Author Topic: Diesel repower and drive considerations  (Read 7790 times)

RonConner

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Diesel repower and drive considerations
« on: February 09, 2013, 08:53:39 AM »
I am considering buying a used yanmar 3gm30f to replace my A4. I least understand my v-drive issues and answers.  Will I need a new vdrive for this early 90's yanmar?  What drive are current P323 owners using with this engine.  Thanks

Dolce_Vita

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Re: Diesel repower and drive considerations
« Reply #1 on: February 09, 2013, 09:41:04 PM »
Hi Ron.  Welcome to the forum.

There was another thread here discussing repower experiences.  I made a lot of comments on replacing an A4 with a diesel:

http://www.pearson323.com/forum/index.php/topic,40.msg175.html#msg175

I'll summarize them here.

Unless you're really dead-set on converting to diesel, consider going back in with a new or rebuilt A4.
Yes, that's right, they're still being made.  And right here in America too.

Moyer Marine  http://www.moyermarine.com/ started casting new A4 blocks about 2 years ago.  They are the purveyor of all things
Atomic 4, and have helped keep 20,000 of the original 40,000 made still in service. Parts and knowledge are readily available.
And they have an extremely active users forum.

Switching out to diesel is a big job, as many other systems are affected (wiring, fuel tank, controls, driveline) and the engine mounts have to be modified. Costs can easily exceed the entire value of the boat.

When my 34-year old A4 finally died a few years ago, after a lot of consideration of diesel alternatives, I went back in with a rebuilt A4.
I've never regretted that decision. 
The 4-cylinder A4 is extremely smooth and quiet, especially when compared to the original Volvo MD11C that Pearson used.
I can work on it with ordinary tools, and spark plugs are a lot cheaper than injectors! :)
And it was about half the cost of a diesel repower.

If you really must go with a diesel, you'll need to replace the Walter V-drive too.  It's engine mounting is not compatible with modern diesel engines.
This usually means a major engine mount modification, as the diesel v-drives that are available have a different "V" angle than the Walter's.  This means either mounting your engine on a different slope, or completely removing and redoing the shaft tube.  My docs show the Walter's "V" angle as 24 degrees. According to Beta Marine, the closest match in a diesel-compatible v-drive is the Hurth ZF15MIV, which only has a 15 degree "V" angle.  Since the Atomic-4 sits at approximately a 9-10 degree angle, the Hurth v-drive will result in an engine mount that is close to level.

In addition, most diesels have a different mounting rail width than the A4.  The exception is Beta Marine, who sells an option that takes the same mounting rails as the A4.  It will NOT be a "drop-in replacement for the A4 in a P-323 however,  due to the V-drive issues.

If you're going with the Yanmar, the 3gm30f is a good choice from a horsepower standpoint.  The rule-of-thumb is 2hp for every 1000lbs of displacement, so our 12,800 lb P-323s (before supplies!) should have an engine with 26-30 hp.  When I was evaluating engines when I was deciding on whether or not to go diesel, my personal pick was the Beta 28.  In either case, the 3 cylinders will give smoother and quieter operation than a 2-cylinder engine.

@(^.^)@  Ed
1977 P-323 #42 "Dolce Vita"
with rebuilt Atomic-4

Dulcinea

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Re: Diesel repower and drive considerations
« Reply #2 on: February 10, 2013, 10:34:16 PM »
The Yanmar may require a different angle for the v drive to maintain a true alignment.  You may need a different transmission and coupling.  Could require some work on the stringers.  I am a diesel fan and recently repowered with a Beta 25 (replaced a Volvo diesel) which is all the power I need to push my boat easily to hull speed in a variety of wind and current conditions.  You will be money ahead, however if you went back with a new A4 and get much more reliability than with a used diesel. 

RonConner

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Re: Diesel repower and drive considerations
« Reply #3 on: February 13, 2013, 04:57:51 PM »
I looked at the Beta but was being steered towards the 28 because of the ability to relocate maintenance items.  How are you finding servicing the 25 since things are on back side of the engine compartment.  I am glad to hear you are finding enough power.  Thanks for your thoughts

Dulcinea

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Re: Diesel repower and drive considerations
« Reply #4 on: February 14, 2013, 12:16:34 PM »
Ron:
Sure not as easy as if it were a straight dirve, but manageable.  The mounted oil pump is relocatable and I might move it to the side of the engine compartment up front.

selene

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Re: Diesel repower and drive considerations
« Reply #5 on: February 15, 2013, 01:08:39 PM »
Great advice on relocating the oil filter.  <sigh> I wish I could relocate the impeller, which is almost inaccessible for me - making a 10-minute change a 1-hour job!

And if you do decide to swap out the engine, try and put aside some time for getting to some of those hard-to-reach places, e.g the fuel tank, steering, etc., maybe repaint the engine compartment. Maybe even soundproof it - mine is not, and is NOISY!

FWIW my boat was repowered with a Westerbeke 3b3.  I don't have a lot of experience living with Yanmar or Beta, so cannot compare directly, but the Westerbeke has worked for me so far, seems a good powerplant.  Incidentally, do heed Ed (Dolce Vitas)'s advice; there is a lot to be said for rebuilding the A4.  I could fix that puppy in my sleep, but learning diesel mechanics - especially when you need to be double jointed and have 6 foot arms to reach anything - is challenging at times!!

Good luck.