I recently repowered my CD28 with a Yanmar 2GM20F. I have a 3 bladed
prop. I have difficulty getting out of my slip beause the boat
backs to port and I need to go to starboard. I am always using a
spring line on the starboad side.When I approach a dock starboard
to and hit reverse the stern swings away to port.
When healing while motor sailing the engine vibrates the boat
significantly at a certain point. I am being sold it does not mean
anything. Also at 1800 RPM the engine vibrates a lot.
Can anyone share some knowledge or experience or advice?
Margrit Keyes
Salacia/CD 28
margrit@earthlink.net
Yanmar engine
Moderator: Jim Walsh
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Mark Yashinsky
Re: Yanmar engine
Look at earlier post on backing of full keel (like Cape Dories) boats. Also, single screw boats have prop walk which gives them a tendancy to turn a particular direction, in reverse. Bet you had these problmes before, maybe just as much (smaller/2 blade prop???). There are two books mentioned earlier, that talk about boat handling under power and offer a number of hints and ideas to use.
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Jim Stull
Re: Yanmar engine
Hi MargritMargrit Keyes wrote: I recently repowered my CD28 with a Yanmar 2GM20F. I have a 3 bladed
prop. I have difficulty getting out of my slip beause the boat
backs to port and I need to go to starboard. I am always using a
spring line on the starboad side.When I approach a dock starboard
to and hit reverse the stern swings away to port.
When healing while motor sailing the engine vibrates the boat
significantly at a certain point. I am being sold it does not mean
anything. Also at 1800 RPM the engine vibrates a lot.
Can anyone share some knowledge or experience or advice?
Margrit Keyes
Salacia/CD 28
I am about to replace the old Yanmar 1GM in the CD27 that I am rebuilding with the same engine you are now using.
In preparation, I have purchased the 3 Yanmar manuals as well as Calder's Diesel book and Dave Gerr's prop book. What you describe happening are clearly mentioned in these sources.
The "prop walk" is normal and can be used to advantage with some experience.
The vibration is another matter. This should be delt with before it possibly causes further problems.
There are very important minimum clearances between the prop and ALL the surrounding surfaces, keel, rudder, deadwood etc.
On my boat I will have to do some trimming and reglassing to meet these critical requirements.
You may wish to check to see where your prop does not meet the clearances detailed in these books and make the necessary changes.
Cheers
Jim
jtstull@earthlink.net
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Bill Goldsmith
Re: Yanmar engine
Margrit,
I echo Jim and Mark's comments.
I have the same engine on my 27. But the issues you raise in your first paragraph about prop walk are universal. My 27 does the exact same thing. I have a two-blade prop--I don't know if the effect is more pronounced with a 3, but my guess is that it would be. My finger float is on the right side of the boat. If I were to apply constant power in reverse to get out of the slip, the prop walk would turn the stern to port, bow to starboard which is the direction I do not want to go.
What I do depends on the conditions. First of all, the wind blows my bow down wind while under power. If the wind is favorable (pushing the bow to port), I just apply a short burst of power to get the boat moving in reverse, and then neutral it, using the rudder and the wind to coax the boat in the right direction while coasting backwards out of the slip. It helps if there is an extra crew member to fend off the boat tied up on my port side.
However if the wind is unfavorable (pushing the bow to starboard), I must use a slip line (spring line, pivot line, warp line, there are many names). It is a tried and true, seamanlike approach that should not be viewed as a nuisance. It helps you control your boat. Keep one ready to use when conditions warrant. I use a 65 foot length of braided polypropylene (10 bucks at Home Depot). It's weak (only 200 pound test) but it floats, it's light and it's cheap, and I wouldn't dream of pressing it into service for any other task, so it's always available.
When arriving back at my slip I try to come in very slowly, because the act of reversing the prop to brake the speed has the same effect as you describe--the stern shoots away to port. In calm conditions I approach the slip slowly and glide right in. Sometimes I don't reverse the engine at all, but instead walk forward, hop on the finger and tie a line around my midship cleat to stop the forward motion. Without midship cleats, you could use a winch or grab a long bow line.
In heavier weather, you have to guage what mixture of power and braun work best for you. If there is a boat on your port side, just make sure you have a couple of well-placed fenders out in case the prop walk pushes you over a bit when landing.
With the vibration, try moving the throttle a little lower or higher. Each engine installation has "sweet spots" and "rough spots." If the rough spots are too rough you may want to have the installation reviewed by a trusted mechanic.
Bill Goldsmith
CD27 #173
Second Chance
goldy@bestweb.net
I echo Jim and Mark's comments.
I have the same engine on my 27. But the issues you raise in your first paragraph about prop walk are universal. My 27 does the exact same thing. I have a two-blade prop--I don't know if the effect is more pronounced with a 3, but my guess is that it would be. My finger float is on the right side of the boat. If I were to apply constant power in reverse to get out of the slip, the prop walk would turn the stern to port, bow to starboard which is the direction I do not want to go.
What I do depends on the conditions. First of all, the wind blows my bow down wind while under power. If the wind is favorable (pushing the bow to port), I just apply a short burst of power to get the boat moving in reverse, and then neutral it, using the rudder and the wind to coax the boat in the right direction while coasting backwards out of the slip. It helps if there is an extra crew member to fend off the boat tied up on my port side.
However if the wind is unfavorable (pushing the bow to starboard), I must use a slip line (spring line, pivot line, warp line, there are many names). It is a tried and true, seamanlike approach that should not be viewed as a nuisance. It helps you control your boat. Keep one ready to use when conditions warrant. I use a 65 foot length of braided polypropylene (10 bucks at Home Depot). It's weak (only 200 pound test) but it floats, it's light and it's cheap, and I wouldn't dream of pressing it into service for any other task, so it's always available.
When arriving back at my slip I try to come in very slowly, because the act of reversing the prop to brake the speed has the same effect as you describe--the stern shoots away to port. In calm conditions I approach the slip slowly and glide right in. Sometimes I don't reverse the engine at all, but instead walk forward, hop on the finger and tie a line around my midship cleat to stop the forward motion. Without midship cleats, you could use a winch or grab a long bow line.
In heavier weather, you have to guage what mixture of power and braun work best for you. If there is a boat on your port side, just make sure you have a couple of well-placed fenders out in case the prop walk pushes you over a bit when landing.
With the vibration, try moving the throttle a little lower or higher. Each engine installation has "sweet spots" and "rough spots." If the rough spots are too rough you may want to have the installation reviewed by a trusted mechanic.
Bill Goldsmith
CD27 #173
Second Chance
Margrit Keyes wrote: I recently repowered my CD28 with a Yanmar 2GM20F. I have a 3 bladed
prop. I have difficulty getting out of my slip beause the boat
backs to port and I need to go to starboard. I am always using a
spring line on the starboad side.When I approach a dock starboard
to and hit reverse the stern swings away to port.
When healing while motor sailing the engine vibrates the boat
significantly at a certain point. I am being sold it does not mean
anything. Also at 1800 RPM the engine vibrates a lot.
Can anyone share some knowledge or experience or advice?
Margrit Keyes
Salacia/CD 28
goldy@bestweb.net
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Mark Yashinsky
Ideas
Who did the repower and has this vibration been present since the repower??? Is it only when motor sailing??? All engine mounts snug (and the mounts are rubber based)??? All nut and bolts should be retorqued after a certain amount of running time. Double check the engine/trans to the prop tube alignment. Was teh cutlass bearing replaced (new tube/shaft???)??? Goldsmith's, Second Chance does have certain rpm's that get things (various cockpit hatches) to resonate. But diesels were never known for smoothness.
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Warren Kaplan
Re: Yanmar engine
I agree with Bill on this. I use a slip line ALL THE TIME when reversing out of my slip since its a tight marina with NO room for error. That line controls the direction my stern goes each and every time no matter what the wind and current conditions are. I'm Bill's poor relative as my CD27 only has a little 8 hp YSM8 (but it does have a 3 bladed prop) and there are sweet and rough spot with the throttle. The hardware on the cockpit lazarettes vibrate like crazy with certain throttle settings. Just move the throttle a little one way or the other and the vibrations should stop.
Warren Kaplan
S/V Sine Qua Non
CD27
Setsail728@aol.com
Warren Kaplan
S/V Sine Qua Non
CD27
Setsail728@aol.com