Yanmar 1GM Riddles (in CD 25D)

[Dean Abramson]

I know that we have been down this road before, but please indulge me. I am confused.

When I first got my 25D about 9 yrs ago, the Yanmar 1GM turned about 3100-3200 prm under load, and moved the boat at what seemed to be hull speed. (My knot meter showed just over 6 knots, which is a little optimistic, but that jived with the reading I got when I was sailing fast, in good wind, on a beam reach. I still get that reading while SAILING fast.)

Gradually it got to the point where I was getting only 2700-2800 rpm, and the boat moved a full knot slower through the water. It also came to deposit more and more black grundge on the transom. I dove under and looked at the prop; it is not fouled.

I have just spent about a thousand bucks chasing this problem, with two different mechanics. The injector was sent out and serviced, the lift pump was serviced, the valves have been adjusted, the air filter checked, the fuel filters replaced, and the second mechanic did an "engine wash," in which he injected some concoction through a syringe into the air intake while it was running. I have also tried additives in the fuel. Net result (hardly any): I am only up to 2900 rpm, and still get lots of grundge on the transom. And the boat goes no faster through the water. Despite optimistic predictions before the work, both mechanics, AFTER the work, decided that the propeller needs work!

From what I can gather, the engine should turn about 3400 under load, and 3600 in neutral. I do actually get MORE than 3600 in neutral. I will probably get the prop re-worked at the end of the season, but unless I want to incur signifigant extra expense (launching/hauling), I will not be able to test the results until next season. Is this a bad idea?

What I don't get is that, IF IT IS the prop, then why did the problem establish itself only gradually? The prop has not changed. (And why did Cape Dory put the wrong prop on the boat?) AND, if I get the prop "detuned" so that the engine turns higher revs under load, isn't there a chance that the boat will then actually go SLOWER? (Since the prop will have less "bite?") The theory is that if the engine cannot turn the recommended revs, then it burns fuel inefficiently, hence the black soot coming out of the exhaust. The first mechanic said he thought that the boat was going hull speed at about 2500 rpm, and anything beyond that was laboring the engine. I don't buy that; the boat used to go a full knot quicker through the water, at the same recorded (by the knot meter) speed as sailing fast. Now it won't.

Any input would be MOST appreciated. And not just from 25D owners. My guess is that a lot of you folks out there know at least as much about this as these two mechanics. Both mechanics, btw, work for Yanmar dealers.



dabramson@mainephoto.com

[Warren Kaplan]

I don't have the same engine, but its a "close cousin". I have a 22 yr old YSM8 on my CD27. Do you sail in salt water? I had to get towed this year because my engine was running but I literally was going nowhere. The weather on the east coast has been so warm that the barnacle fouling problem on the props in my marina has become epidemic. My yard manager knew the problem as soon as we got in from the tow. The engine checked out fine (by my mechanic) and the next day we sent a diver down and the prop was a mess. He cleaned the prop and the boat bottom too (also slimed up) and..low and behold...no more problem! Maybe this doesn't apply to you in your "environment". But if you think it might, send a diver down and it may "cure" your problem and save the rest of your season. By the way, my diver cost me $65. If I knew that earlier I'd send him down once a month during the warm weather. Perhaps this will help. Hope so.
Warren Kaplan
Sine Qua Non
CD27
Oyster Bay Harbor, NY



Setsail728@aol.com

[Dean Abramson]

I did dive down and look. The prop is clear.



dabramson@mainephoto.com

[Gary L.]

I did dive down and look. The prop is clear.

Dean,

Are you overheating? Are you experiencing more vibration? You state that you have the power in neutral, but not under load. If your prop is not fouled (clean of barnacles and weed), it could be your shaft.

I experienced the same with Red Witch III recently and posted that I dove and cleaned the prop and changed thermostat (for overheating). When I cleaned the prop, I also cleaned the inch or two of exposed shaft at the cutlass bearing using the extra course 3M scrubber.

I don't know if this helps any, but keep us informed.

Gary Lapine
Red Witch III
CD30C, #339
Somerset, MA



dory26@attbi.com

[Dean Abramson]

I have had no overheating at all. And I have had no indication that the shaft or stuffing box needs adjusting. No excess dripping; no lack of dripping. No excess vibration. In fact, the engine sounds and "feels" pretty good. Just slowish under load, and putting out this grundge which seems more carbon-ish than oil-ish.



dabramson@mainephoto.com

[D Gates]

I ran my 25D with 1GM over 5,000 hrs with a 2 blade prop. I experimented with other props. The bottom line is as hull resistance (drag) increases .. engine load also increases. I found that @ 2,500 to 2,600 rpms was the most efficeint and best overall performance. The 1 knot you might have gained was with a fresh cutless bearing etc; but your fuel efficiency would be much lower at max rpm. I have seen run many sailboats with diesel engines over the past 30 years and all diesel display this characteristic. (Even my personal car is a diesel and fuel economy goes in the bucket after 75 mph.
Less pitch will give you more power and more rpms.. with a full displcement hull speed will remain the same which is close to theoritical.



dsgsgt@sisna.com

[John R.]

There are only a few things that can cause the black carbon build up. Check for dirty or poor fuel quality, transmission problems (drag and loading), running rich, exhaust restrictions, dirty or clogged air filter.

More than likely most of that stuff should be fine after having two Yanmar mechanics checking things out. Since you say it runs okay in neutral my focus would now be somewhere in the driveline as a beginning of a process of elimination. If the prop is clean and it hasn't been damaged then there should be no problem with it. Make sure the engine hasn't shifted on it's mounts and you can eliminate alignment problems. Perhaps something in the transmission could be giving you problems.

FWIW - It sounds to me like you have a drag or resistance problem and that makes me think transmission, alignment, shaft, cutless etc.

I know that we have been down this road before, but please indulge me. I am confused.

When I first got my 25D about 9 yrs ago, the Yanmar 1GM turned about 3100-3200 prm under load, and moved the boat at what seemed to be hull speed. (My knot meter showed just over 6 knots, which is a little optimistic, but that jived with the reading I got when I was sailing fast, in good wind, on a beam reach. I still get that reading while SAILING fast.)

Gradually it got to the point where I was getting only 2700-2800 rpm, and the boat moved a full knot slower through the water. It also came to deposit more and more black grundge on the transom. I dove under and looked at the prop; it is not fouled.

I have just spent about a thousand bucks chasing this problem, with two different mechanics. The injector was sent out and serviced, the lift pump was serviced, the valves have been adjusted, the air filter checked, the fuel filters replaced, and the second mechanic did an "engine wash," in which he injected some concoction through a syringe into the air intake while it was running. I have also tried additives in the fuel. Net result (hardly any): I am only up to 2900 rpm, and still get lots of grundge on the transom. And the boat goes no faster through the water. Despite optimistic predictions before the work, both mechanics, AFTER the work, decided that the propeller needs work!

From what I can gather, the engine should turn about 3400 under load, and 3600 in neutral. I do actually get MORE than 3600 in neutral. I will probably get the prop re-worked at the end of the season, but unless I want to incur signifigant extra expense (launching/hauling), I will not be able to test the results until next season. Is this a bad idea?

What I don't get is that, IF IT IS the prop, then why did the problem establish itself only gradually? The prop has not changed. (And why did Cape Dory put the wrong prop on the boat?) AND, if I get the prop "detuned" so that the engine turns higher revs under load, isn't there a chance that the boat will then actually go SLOWER? (Since the prop will have less "bite?") The theory is that if the engine cannot turn the recommended revs, then it burns fuel inefficiently, hence the black soot coming out of the exhaust. The first mechanic said he thought that the boat was going hull speed at about 2500 rpm, and anything beyond that was laboring the engine. I don't buy that; the boat used to go a full knot quicker through the water, at the same recorded (by the knot meter) speed as sailing fast. Now it won't.

Any input would be MOST appreciated. And not just from 25D owners. My guess is that a lot of you folks out there know at least as much about this as these two mechanics. Both mechanics, btw, work for Yanmar dealers.

[Boyd]

Hi Dean...

I dont have that engine but here are some thoughts about why you may be having problems.

Out of all the mechanics work did either of them do a compression test? This could be part of the problem. Does the engine start hard? Poor compression would result in lower hp output and hard starting. If this checks out ok then we have eliminated this possible source.

What type of filters have you got on the engine? Lack of top end can be from plugged filters. You may have got a load of bad fuel. Changing the filters would help the problem but only for a few hours. I clogged up two primary filters in less than 4 hours running time. Had lots of crud in the tank. I would suggest pumping out the tank and filling with all new stuff. Then replace the filters. Its a DIY job. It would eleminate the fuel as a source.

Check the exhaust system for clogs.. especially at the water injection point.

If everything is working well (prop, trans, engine, etc) you should achieve hull speed at about 80% max rpm. At 100% max some light black smoke is ok. You should not be crusing at much over 80%. Save the 100% for Beta mode situations. (Beta mode... Big eyes tight ass).

Let us know what you find...

Boyd
s/v Tern
CD30 MkII
Fort Lauderdale, Fla.

I know that we have been down this road before, but please indulge me. I am confused.

When I first got my 25D about 9 yrs ago, the Yanmar 1GM turned about 3100-3200 prm under load, and moved the boat at what seemed to be hull speed. (My knot meter showed just over 6 knots, which is a little optimistic, but that jived with the reading I got when I was sailing fast, in good wind, on a beam reach. I still get that reading while SAILING fast.)

Gradually it got to the point where I was getting only 2700-2800 rpm, and the boat moved a full knot slower through the water. It also came to deposit more and more black grundge on the transom. I dove under and looked at the prop; it is not fouled.

I have just spent about a thousand bucks chasing this problem, with two different mechanics. The injector was sent out and serviced, the lift pump was serviced, the valves have been adjusted, the air filter checked, the fuel filters replaced, and the second mechanic did an "engine wash," in which he injected some concoction through a syringe into the air intake while it was running. I have also tried additives in the fuel. Net result (hardly any): I am only up to 2900 rpm, and still get lots of grundge on the transom. And the boat goes no faster through the water. Despite optimistic predictions before the work, both mechanics, AFTER the work, decided that the propeller needs work!

From what I can gather, the engine should turn about 3400 under load, and 3600 in neutral. I do actually get MORE than 3600 in neutral. I will probably get the prop re-worked at the end of the season, but unless I want to incur signifigant extra expense (launching/hauling), I will not be able to test the results until next season. Is this a bad idea?

What I don't get is that, IF IT IS the prop, then why did the problem establish itself only gradually? The prop has not changed. (And why did Cape Dory put the wrong prop on the boat?) AND, if I get the prop "detuned" so that the engine turns higher revs under load, isn't there a chance that the boat will then actually go SLOWER? (Since the prop will have less "bite?") The theory is that if the engine cannot turn the recommended revs, then it burns fuel inefficiently, hence the black soot coming out of the exhaust. The first mechanic said he thought that the boat was going hull speed at about 2500 rpm, and anything beyond that was laboring the engine. I don't buy that; the boat used to go a full knot quicker through the water, at the same recorded (by the knot meter) speed as sailing fast. Now it won't.

Any input would be MOST appreciated. And not just from 25D owners. My guess is that a lot of you folks out there know at least as much about this as these two mechanics. Both mechanics, btw, work for Yanmar dealers.

Boyd@wbta.cc

[Bill]

Dean

At what RPM do you run the engine? I have run mine ar or above 3000 only once or twice and only then to see if it would do that. I typically run about 2800 and that gives me 5.5ish (by GPS) knots if the hull is fairly clean....I compute hull speed at 5.3 ish (Sqrt of 19.5x1.2ish)????? Should we expect more than that?????

Fair Winds
Bill

I know that we have been down this road before, but please indulge me. I am confused.

When I first got my 25D about 9 yrs ago, the Yanmar 1GM turned about 3100-3200 prm under load, and moved the boat at what seemed to be hull speed. (My knot meter showed just over 6 knots, which is a little optimistic, but that jived with the reading I got when I was sailing fast, in good wind, on a beam reach. I still get that reading while SAILING fast.)

Gradually it got to the point where I was getting only 2700-2800 rpm, and the boat moved a full knot slower through the water. It also came to deposit more and more black grundge on the transom. I dove under and looked at the prop; it is not fouled.

I have just spent about a thousand bucks chasing this problem, with two different mechanics. The injector was sent out and serviced, the lift pump was serviced, the valves have been adjusted, the air filter checked, the fuel filters replaced, and the second mechanic did an "engine wash," in which he injected some concoction through a syringe into the air intake while it was running. I have also tried additives in the fuel. Net result (hardly any): I am only up to 2900 rpm, and still get lots of grundge on the transom. And the boat goes no faster through the water. Despite optimistic predictions before the work, both mechanics, AFTER the work, decided that the propeller needs work!

From what I can gather, the engine should turn about 3400 under load, and 3600 in neutral. I do actually get MORE than 3600 in neutral. I will probably get the prop re-worked at the end of the season, but unless I want to incur signifigant extra expense (launching/hauling), I will not be able to test the results until next season. Is this a bad idea?

What I don't get is that, IF IT IS the prop, then why did the problem establish itself only gradually? The prop has not changed. (And why did Cape Dory put the wrong prop on the boat?) AND, if I get the prop "detuned" so that the engine turns higher revs under load, isn't there a chance that the boat will then actually go SLOWER? (Since the prop will have less "bite?") The theory is that if the engine cannot turn the recommended revs, then it burns fuel inefficiently, hence the black soot coming out of the exhaust. The first mechanic said he thought that the boat was going hull speed at about 2500 rpm, and anything beyond that was laboring the engine. I don't buy that; the boat used to go a full knot quicker through the water, at the same recorded (by the knot meter) speed as sailing fast. Now it won't.

Any input would be MOST appreciated. And not just from 25D owners. My guess is that a lot of you folks out there know at least as much about this as these two mechanics. Both mechanics, btw, work for Yanmar dealers.

cd25d@rhapsodysails.com

[BobM]

I know that we have been down this road before, but please indulge me. I am confused.

When I first got my 25D about 9 yrs ago, the Yanmar 1GM turned about 3100-3200 prm under load, and moved the boat at what seemed to be hull speed. (My knot meter showed just over 6 knots, which is a little optimistic, but that jived with the reading I got when I was sailing fast, in good wind, on a beam reach. I still get that reading while SAILING fast.)

Gradually it got to the point where I was getting only 2700-2800 rpm, and the boat moved a full knot slower through the water. It also came to deposit more and more black grundge on the transom. I dove under and looked at the prop; it is not fouled.

I have just spent about a thousand bucks chasing this problem, with two different mechanics. The injector was sent out and serviced, the lift pump was serviced, the valves have been adjusted, the air filter checked, the fuel filters replaced, and the second mechanic did an "engine wash," in which he injected some concoction through a syringe into the air intake while it was running. I have also tried additives in the fuel. Net result (hardly any): I am only up to 2900 rpm, and still get lots of grundge on the transom. And the boat goes no faster through the water. Despite optimistic predictions before the work, both mechanics, AFTER the work, decided that the propeller needs work!

From what I can gather, the engine should turn about 3400 under load, and 3600 in neutral. I do actually get MORE than 3600 in neutral. I will probably get the prop re-worked at the end of the season, but unless I want to incur signifigant extra expense (launching/hauling), I will not be able to test the results until next season. Is this a bad idea?

What I don't get is that, IF IT IS the prop, then why did the problem establish itself only gradually? The prop has not changed. (And why did Cape Dory put the wrong prop on the boat?) AND, if I get the prop "detuned" so that the engine turns higher revs under load, isn't there a chance that the boat will then actually go SLOWER? (Since the prop will have less "bite?") The theory is that if the engine cannot turn the recommended revs, then it burns fuel inefficiently, hence the black soot coming out of the exhaust. The first mechanic said he thought that the boat was going hull speed at about 2500 rpm, and anything beyond that was laboring the engine. I don't buy that; the boat used to go a full knot quicker through the water, at the same recorded (by the knot meter) speed as sailing fast. Now it won't.

Any input would be MOST appreciated. And not just from 25D owners. My guess is that a lot of you folks out there know at least as much about this as these two mechanics. Both mechanics, btw, work for Yanmar dealers.

=================================================

Dean:

I suspect your problem may be bad fuel. This weekend we were out over night on Ranger and coming into our river with the engine hot I tried to run her to max rpm to see what she would do. I noticed that she maxed out at around 2600 RPM. I was making about 6.1 knots according to my knot meter, which I know is accurate. Earlier in the season I was able to hit 3000 RPM under load. I have not added any fuel to the tank this summer as I was trying to burn my old fuel before adding new fresh fuel. I also am having a lot of sooting on the transom, which again tells me I have bad fuel. I would suggest that you pump out your tank and replace with fresh fuel and cetan boost with biocide additives. Also don't forget to add some Marvel Mystery oil as a upper cylinder lubricant for your valves. Make sure your fuel is fresh from a source that pumps a lot of diesel fuel and not lying around in a tank for a while. Then let me know how your engine is running. I believe the first thing you will notice is how much more responsive the engine is to throttle and you should also pick up some more RPM's.

Bob
Ranger #144
CD25D 1984



ranger1442@hotmail.com

[BobM]

Dean

At what RPM do you run the engine? I have run mine ar or above 3000 only once or twice and only then to see if it would do that. I typically run about 2800 and that gives me 5.5ish (by GPS) knots if the hull is fairly clean....I compute hull speed at 5.3 ish (Sqrt of 19.5x1.2ish)????? Should we expect more than that?????

Fair Winds
Bill

============================================================

Bill:

As displacement hulls our CD25D's should hit theorically max hull speed at 5.84 knots, however I know at max RPM I am hitting a smidge over 6 Knots. At that point I am pushing a large wake and not able to break out of the quarter wave.

Bob
Ranger #144
CD252D 1984



ranger1442@hotmail.com

[BobM]

I don't have the same engine, but its a "close cousin". I have a 22 yr old YSM8 on my CD27. Do you sail in salt water? I had to get towed this year because my engine was running but I literally was going nowhere. The weather on the east coast has been so warm that the barnacle fouling problem on the props in my marina has become epidemic. My yard manager knew the problem as soon as we got in from the tow. The engine checked out fine (by my mechanic) and the next day we sent a diver down and the prop was a mess. He cleaned the prop and the boat bottom too (also slimed up) and..low and behold...no more problem! Maybe this doesn't apply to you in your "environment". But if you think it might, send a diver down and it may "cure" your problem and save the rest of your season. By the way, my diver cost me $65. If I knew that earlier I'd send him down once a month during the warm weather. Perhaps this will help. Hope so.
Warren Kaplan
Sine Qua Non
CD27
Oyster Bay Harbor, NY

-----------------------------------------------------------------

Hi Warren:

Good afternoon to ya! My wasn't this weekend a dandy one? I was thinking of you yesterday while passing off Bayshore in a very pleasant 12 to 15 knots of steady southwest wind clocking 5.8 knots to windward. But then I remembered how you abandoned our steady winds for the unpredictable north shore winds of LI Sound. I was thinking this is as good as it gets and worth all the work we do over the winter and spring.

So you say the "east coast has been so warm that the barnacle fouling problem on the props in my marina has become epidemic.", welcome to the waters of LI Sound. This is not untypical for that to happen up north, never had any barnacles fouling props down on the GSB as the ocean keeps us cooler. Deep water of course also has it's advantages.

Best regards,

Bob
Ranger #144
CD25D 1984



ranger1442@hotmail.com

[Chessy MacBay]

I am betting your fuel is old and the c-tane rating is in the dumper. Pump the fuel tank out and get a fresh tank of deisel. Don't forget the bio-bor.

[Larry DeMers]

The formula for max hull speed is actually Sqrt of LWL (19.5 for the 25D)x1.34. This will give a top end of 5.92 kts I believe.
1.34 for the constant has been around for awhile now, and cruising boats seem to fall in the 1.25-1.34 range for that constant.

I think the first thing I need to know is what the spec is for that engine as far as max rpm. Cruising speed should be about 75% of that rpm for best mileage and life of the engine.

Larry DeMers
s/v DeLaMer
Cape Dory 30

Dean

At what RPM do you run the engine? I have run mine ar or above 3000 only once or twice and only then to see if it would do that. I typically run about 2800 and that gives me 5.5ish (by GPS) knots if the hull is fairly clean....I compute hull speed at 5.3 ish (Sqrt of 19.5x1.2ish)????? Should we expect more than that?????

Fair Winds
Bill

I know that we have been down this road before, but please indulge me. I am confused.

When I first got my 25D about 9 yrs ago, the Yanmar 1GM turned about 3100-3200 prm under load, and moved the boat at what seemed to be hull speed. (My knot meter showed just over 6 knots, which is a little optimistic, but that jived with the reading I got when I was sailing fast, in good wind, on a beam reach. I still get that reading while SAILING fast.)

Gradually it got to the point where I was getting only 2700-2800 rpm, and the boat moved a full knot slower through the water. It also came to deposit more and more black grundge on the transom. I dove under and looked at the prop; it is not fouled.

I have just spent about a thousand bucks chasing this problem, with two different mechanics. The injector was sent out and serviced, the lift pump was serviced, the valves have been adjusted, the air filter checked, the fuel filters replaced, and the second mechanic did an "engine wash," in which he injected some concoction through a syringe into the air intake while it was running. I have also tried additives in the fuel. Net result (hardly any): I am only up to 2900 rpm, and still get lots of grundge on the transom. And the boat goes no faster through the water. Despite optimistic predictions before the work, both mechanics, AFTER the work, decided that the propeller needs work!

From what I can gather, the engine should turn about 3400 under load, and 3600 in neutral. I do actually get MORE than 3600 in neutral. I will probably get the prop re-worked at the end of the season, but unless I want to incur signifigant extra expense (launching/hauling), I will not be able to test the results until next season. Is this a bad idea?

What I don't get is that, IF IT IS the prop, then why did the problem establish itself only gradually? The prop has not changed. (And why did Cape Dory put the wrong prop on the boat?) AND, if I get the prop "detuned" so that the engine turns higher revs under load, isn't there a chance that the boat will then actually go SLOWER? (Since the prop will have less "bite?") The theory is that if the engine cannot turn the recommended revs, then it burns fuel inefficiently, hence the black soot coming out of the exhaust. The first mechanic said he thought that the boat was going hull speed at about 2500 rpm, and anything beyond that was laboring the engine. I don't buy that; the boat used to go a full knot quicker through the water, at the same recorded (by the knot meter) speed as sailing fast. Now it won't.

Any input would be MOST appreciated. And not just from 25D owners. My guess is that a lot of you folks out there know at least as much about this as these two mechanics. Both mechanics, btw, work for Yanmar dealers.

demers@sgi.com

[Larry DeMers]

Theoretically, if you stuck a jet engine on the transom, you could plane that beast..but it would take all of that power to do so (would be a kick to see though).
As the boat tries to exceed hull speed, it squats in the water more, while trying damn hard to climb up and out of the hole it has carved for itself. Add more HP and it will climb up that wall in front..a bit. Add more HP..it's a logrithmic function I believe, so the amount you add goes up very fast, for a given gain...and the stern is way down in the hole, the nbow way up and above the water, and the boat may even teeter on the brink of planing off (we're neglecting wetted surface effects and that pesky keel here). Lasers and a few other keel boats do plane off when overdriven by wind. They lose control in a limited way, and I saw one skitter across the wind while beating. It just flew though.

Larry DeMers
s/v DeLaMer
Cape Dory 30

Dean

At what RPM do you run the engine? I have run mine ar or above 3000 only once or twice and only then to see if it would do that. I typically run about 2800 and that gives me 5.5ish (by GPS) knots if the hull is fairly clean....I compute hull speed at 5.3 ish (Sqrt of 19.5x1.2ish)????? Should we expect more than that?????

Fair Winds
Bill

============================================================

Bill:

As displacement hulls our CD25D's should hit theorically max hull speed at 5.84 knots, however I know at max RPM I am hitting a smidge over 6 Knots. At that point I am pushing a large wake and not able to break out of the quarter wave.

Bob
Ranger #144
CD252D 1984

demers@sgi.com