Yanmar 1GM Questions

[Bob Dugan]

I've noticed a couple of things about my engine, and I'm wondering if any of you have seen or heard about anything like this:

Problem #1: Different Max RPMs in and out of gear
-------------------------------------------------
In gear the RPMs go up to 3400, but I can't get them to 3600. Out of gear I can't get the RPMs much higher than 2200.

Problem #2: Engine overheating at less than maximum load
--------------------------------------------------------
If I let the engine run above 2500 rpm in gear, in less than an hour the overheating light comes on. To make the light go off, I reduce the RPMs... I seem to be able to run forever at 2400 rpm.

I'm noticing some smoke coming from the exhaust even at 2400 rpm. After 30 hours on the engine last week, I can see a little bit of black residue on the transom.

*** I think this problem is because the boat is over-propped. A previous owner put a 3 blade prop on (I still have the original two blade in a box)... a Mack-Boring instructor explained that if you put a bigger blade on your boat you are asking for trouble. Apparenlty there is a delicate balance between blade size and the transmission because the transmission and the engine have an agreement about the number of rpms the propeller shaft will spin in relation to the engine rpms. This is called the "reduction ratio". If the prop is too big for the transmission then the engine has to work too hard to maintain this reduction ratio. The result is smoke and overheating at high rpms, and a smaller amount of smoke, and slow gradual engine damage at lower rpms.

Problem #3 - Sad looking engine mounts
---------------------------------------
Two of the four engine mounts on the boat look rusted and the rubber looks brittle. Has anyone replaced these on a 25D? Where did you get the mounts? How did you do it?

Any help with these questions would be great!

Thanks

Bob Dugan
"Cricket" CD25D #92
Wayland, MA



bdugan@stepzero.com

[Bill]

Hi Bob

Here is a link to a thread from several years ago. I replaced my mounts and if you search under "engine" then "mounts" and finally 1GM you will get to several threads. TOrrenson Marine is very good, but the standard 1gm Mounts WILL NOT work. so tell them that.

I have the part numbers on the boat and can get them this weekend. But maybe someone else can chime in before then.

Hope this helps.

<A HREF="http://www.toolworks.com/cgi-bin/tw/wwb ... 68">Engine Thread Link</A>

and here is a link to Torrensen Marine <a href="http://www.marinedieseldirect.com/yanmar/">Torrensen Marine</A>

Fair Winds

Bill
Captain Commanding
S/V Rhapsody (the Original)
CD25D #148
Oklahoma Contingent of the NE Fleet of the CDSOA
Galley Wench Evening Light
<A HREF="http.www.applegatemarina.com">Kerr Lake, OK (Oklahoma's Outlet to the Sea)</A>

I've noticed a couple of things about my engine, and I'm wondering if any of you have seen or heard about anything like this:

Problem #1: Different Max RPMs in and out of gear
-------------------------------------------------
In gear the RPMs go up to 3400, but I can't get them to 3600. Out of gear I can't get the RPMs much higher than 2200.

Problem #2: Engine overheating at less than maximum load
--------------------------------------------------------
If I let the engine run above 2500 rpm in gear, in less than an hour the overheating light comes on. To make the light go off, I reduce the RPMs... I seem to be able to run forever at 2400 rpm.

I'm noticing some smoke coming from the exhaust even at 2400 rpm. After 30 hours on the engine last week, I can see a little bit of black residue on the transom.

*** I think this problem is because the boat is over-propped. A previous owner put a 3 blade prop on (I still have the original two blade in a box)... a Mack-Boring instructor explained that if you put a bigger blade on your boat you are asking for trouble. Apparenlty there is a delicate balance between blade size and the transmission because the transmission and the engine have an agreement about the number of rpms the propeller shaft will spin in relation to the engine rpms. This is called the "reduction ratio". If the prop is too big for the transmission then the engine has to work too hard to maintain this reduction ratio. The result is smoke and overheating at high rpms, and a smaller amount of smoke, and slow gradual engine damage at lower rpms.

Problem #3 - Sad looking engine mounts
---------------------------------------
Two of the four engine mounts on the boat look rusted and the rubber looks brittle. Has anyone replaced these on a 25D? Where did you get the mounts? How did you do it?

Any help with these questions would be great!

Thanks

Bob Dugan
"Cricket" CD25D #92
Wayland, MA

cd25d@rhapsodysails.com

[Bob B]

In gear and out of gear doesn't make much sense to me. Mine is just the opposite, I can get more RPMs from her out of gear.

I usually cruise at 2,400RPM-2,600RPM. I have had no problem with this boat, also a 25D. I did have a CD 27 and it put out black smoke when I overloaded the engine. It also had worn rings and did not have good compression so would smoke some while running it hard. I ended up having it overhauled and this solved the problems.

I do think that your 3 blade prop may be a bit much. Try the smaller one and see if there is a difference. If not then you may be looking at some more extensive problems.

Good luck with it.

Bob Bundy
CD25D Tiva
Charleston, SC



BundyR@aol.com

[Bob Dugan]

Hi Bill,

I have the part numbers on the boat and can get them this weekend. But maybe someone else can chime in before then.

I sure would appreciate those part numbers... thanks!



bdugan@stepzero.com

[Randy Bates]

I don't think it's a good idea to try to run an engine to max rpms w/o any load. This goes for ALL engines. A wrong prop is either like starting off in your car in third gear or trying to go 65 in first. Neither is good. You'll either spin the engine too much or lug it. It's the torque curve of the engine and the final gear ratio of the transmission that the prop must match.

I've noticed a couple of things about my engine, and I'm wondering if any of you have seen or heard about anything like this:

Problem #1: Different Max RPMs in and out of gear
-------------------------------------------------
In gear the RPMs go up to 3400, but I can't get them to 3600. Out of gear I can't get the RPMs much higher than 2200.

Problem #2: Engine overheating at less than maximum load
--------------------------------------------------------
If I let the engine run above 2500 rpm in gear, in less than an hour the overheating light comes on. To make the light go off, I reduce the RPMs... I seem to be able to run forever at 2400 rpm.

I'm noticing some smoke coming from the exhaust even at 2400 rpm. After 30 hours on the engine last week, I can see a little bit of black residue on the transom.

*** I think this problem is because the boat is over-propped. A previous owner put a 3 blade prop on (I still have the original two blade in a box)... a Mack-Boring instructor explained that if you put a bigger blade on your boat you are asking for trouble. Apparenlty there is a delicate balance between blade size and the transmission because the transmission and the engine have an agreement about the number of rpms the propeller shaft will spin in relation to the engine rpms. This is called the "reduction ratio". If the prop is too big for the transmission then the engine has to work too hard to maintain this reduction ratio. The result is smoke and overheating at high rpms, and a smaller amount of smoke, and slow gradual engine damage at lower rpms.

Problem #3 - Sad looking engine mounts
---------------------------------------
Two of the four engine mounts on the boat look rusted and the rubber looks brittle. Has anyone replaced these on a 25D? Where did you get the mounts? How did you do it?

Any help with these questions would be great!

Thanks

Bob Dugan
"Cricket" CD25D #92
Wayland, MA

randy.bates@baesystems.com

[Dean Abramson]

On the revs question, could it be simply that you cannot push the throttle as far forward when the gear-shift button is out? (That is the case on my 25D.) For this reason, I start my engine by pushing the lever aft (out of gear). You might try that, briefly. But I agree that to rev it high with no load is not good. Just try it for a second, after the engine is warmed up, to see if you get more revs. If so, then either that button is in the way, or there is something loose in the linkage. That's my guess, anyway. I find that my engine starts more readily with a bit more "gas," so I do it that way, but as soon as it catches, I back off the revs instantly. I wind up with less smoke and grundge this way. I do have a general problem with the transom getting a black smudge. Interestingly, it gets it on a line that is above the resting waterline, but rather at what seems to be the motoring waterline, and NOT by the exhaust pipe opening, but on the opposite side! The grundge applies itself while I am underway. I think that the exhaust grundge mixes with the stern wake, and "paints" this stuff on as I motor. I know this sounds nuts. But the other 25D in my marina has this exact same grundge-pattern on her transom too. Any theories out there? Anyway, my impression is that this particular one-cylinder diesel just doesn't run that clean. But the darn thing seems perfectly happy in her slovenly ways, and runs just fine. If it ever dies, I will probably replace it with the Yanmar 1GM10. I like the engine a lot.

Dean Abramson
"Mariah"
25D

I've noticed a couple of things about my engine, and I'm wondering if any of you have seen or heard about anything like this:

Problem #1: Different Max RPMs in and out of gear
-------------------------------------------------
In gear the RPMs go up to 3400, but I can't get them to 3600. Out of gear I can't get the RPMs much higher than 2200.

Problem #2: Engine overheating at less than maximum load
--------------------------------------------------------
If I let the engine run above 2500 rpm in gear, in less than an hour the overheating light comes on. To make the light go off, I reduce the RPMs... I seem to be able to run forever at 2400 rpm.

I'm noticing some smoke coming from the exhaust even at 2400 rpm. After 30 hours on the engine last week, I can see a little bit of black residue on the transom.

*** I think this problem is because the boat is over-propped. A previous owner put a 3 blade prop on (I still have the original two blade in a box)... a Mack-Boring instructor explained that if you put a bigger blade on your boat you are asking for trouble. Apparenlty there is a delicate balance between blade size and the transmission because the transmission and the engine have an agreement about the number of rpms the propeller shaft will spin in relation to the engine rpms. This is called the "reduction ratio". If the prop is too big for the transmission then the engine has to work too hard to maintain this reduction ratio. The result is smoke and overheating at high rpms, and a smaller amount of smoke, and slow gradual engine damage at lower rpms.

Problem #3 - Sad looking engine mounts
---------------------------------------
Two of the four engine mounts on the boat look rusted and the rubber looks brittle. Has anyone replaced these on a 25D? Where did you get the mounts? How did you do it?

Any help with these questions would be great!

Thanks

Bob Dugan
"Cricket" CD25D #92
Wayland, MA

dabramson@mainephoto.com

[Bill]

Hello Bob

I am cross posting this information just in case anyone else needs it. Here is a reply I sent Bob about 1GM Engine Mounts that were direct replacement for those found aboard Rhapsody (my 25D).

Hello Bob you are in luck

I found a receipt from where I ordered the mounts.

part number is Bus/DF 265 @ $54 each (in 1997).....

Now the disclaimer....thats was the direct replacement for the one aboard Rhapsody (a 25D).

Hope this helps

Bill

Problem #3 - Sad looking engine mounts
---------------------------------------
Two of the four engine mounts on the boat look rusted and the rubber looks brittle. Has anyone replaced these on a 25D? Where did you get the mounts? How did you do it?

cd25d@rhapsodysails.com