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Old 24-10-2015, 06:49   #1
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Replacement Engine for Volvo MD3B

So I adopted a wooden sailboat a few weeks ago specs are 34 ft 10 ft breadth 4'3" depthgross tonnage was 8.18 net/ registered tonnage was 5.56. Motor claims like 28 HP at the prop. What can I use as a replacement? I am not concerned about speed. Would a 15 hp yanmar suffice? Or do I need to stay at least 30 HP to run hull speed calculated at like 5.5 knots..I plan on mostly learning on the Chesapeake Bay, and at some point maybe doing some longer trips. I just need to know what to expect out of a 15 hp diesel.....will i be vastly disappointed? I am just on a shoestring budget, and the motor in it now the volvo, is stuck, I have freed it somewhat, but I really do not expect it to be up to using without removing and overhauling it..which I can do. So would a yanmar 15 suffice for now? or should I go ahead and keep looking for something larger? thanks for any help! Jeff
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Old 24-10-2015, 16:00   #2
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re: Replacement Engine for Volvo MD3B

WE had an MD2B with a two bladed prop in our Westsail 32, 10 tons displacement. It was fine for us but I'm not a big engine user. Never had a problem powering at 5 knots in calm conditions and about a 1.2 gallon an hour consumption. The one or two times we had to buck into a chop and strong headwind, motor sailed largely because the motion was easier.

Delivered 2 Westsails from SF to SoCal, one with an MD3B and the other with a 4-107. No question, you could do more with the extra power and big three bladed prop like stop the boat under full sail in Santa Ana winds by throwing the bigger engine into reverse and red lining it. Not something I did but a clueless owner who tried to sail up Newport Beach Bay into a narrow deadend channel.

Today people seem to think that a bigger engine is a replacement for good seamanship and are going for bigger and bigger engines. Seem to recall someone re-enginging a boat similar to yours questioning whether he should go from the current 50hp engine to a 70hp. Personally think for optimum power and resaie value an engine around 25hp would be the best size. That is what we've go on our current 7 ton boat and it has been just right. If you want the best fuel economy and are content to use the engine for getting in and out of the slip and no wind condition powering then a 15hp engine would suffice.
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Old 24-10-2015, 16:06   #3
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re: Replacement Engine for Volvo MD3B

I'll second roverhi.

Our boat is 32', 7.5tons empty, with a 28 horse engine that I normally only utilize to about 10 horsepower of.The extra power is nice but not mandatory, I feel on my boat with a 15 horse engine I could still do what I needed to do, it just might take longer at times.


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Old 24-10-2015, 16:30   #4
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re: Replacement Engine for Volvo MD3B

The better the boat and the sailor, the less engine one needs. Another huge factor is how much wind / wave / contrary tidal current you may encounter.

You will see anything from 2 to 5 hp per metric ton pretty common. E.g. us in a 4t metric boat are fine with a 12 hp donkey. I think we normally use only btw 6 and 8 hp out of it. This would be like having a 16hp engine in your boat.

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Old 24-10-2015, 16:36   #5
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re: Replacement Engine for Volvo MD3B

Then again, if you think you can fix that old VP, I would at least give it a serious try. I think old cast iron VP are good engines.

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Old 24-10-2015, 17:21   #6
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re: Replacement Engine for Volvo MD3B

Interested in selling some parts off md3b
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Old 24-10-2015, 17:25   #7
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re: Replacement Engine for Volvo MD3B

I will probably overhaul it as a winter project . as I have a new alternator, and 3 (1 bad) transmissions...
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Old 24-10-2015, 17:27   #8
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re: Replacement Engine for Volvo MD3B

But I may put a yanmar half the size for now. There are lots more of them around here.
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Old 24-10-2015, 18:01   #9
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re: Replacement Engine for Volvo MD3B

Quote:
Originally Posted by retired2015 View Post
But I may put a yanmar half the size for now. There are lots more of them around here.

You could probably buy a yanmar for the price of gasket on the old volvo


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Old 24-10-2015, 18:07   #10
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re: Replacement Engine for Volvo MD3B

Im thinking parts availability may be better with a yanmart too......
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Old 24-10-2015, 20:35   #11
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re: Replacement Engine for Volvo MD3B

I love those old MD Series Volvos. If there was a way to save it, I'd go for it. The best thing is they can be hand cranked which I did for 10 years with the MD2. The extra mass of the MD3 takes a bit more oomph to get rotating and start but I've done it. The cylinders are separate and can be removed individually. You can do a near total rebuild in the boat all except the crank and crank bearings. Volvo did it on mine after it ingested water and shortened the rods. As others have said, the real issue for a rebuild is cost and availability of parts. The engine has been out of production for around 30 years so parts have got to be getting scarce and Volvo is notorious for rip off replacement part pricing.

One benefit of a new engine is it will be considerably lighter for similar horsepower. My Yanmar 3GM30 feels like it ways less than the flywheel on the MD Volvo. Of course, it's that flywheel and compression releases that make it possible to hand start the Volvo.

If you have an interest, still have a crank for the MD2 which I think will fit all the hand crank Volvos in the MD Series.
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Old 25-10-2015, 03:22   #12
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re: Replacement Engine for Volvo MD3B

I do not have the hand crank, this is what makes it difficult, I do have a giant breaker and socket, but in order to rock it in direction of travel, if I push too hard it unscrews the flywheel nut, and id prefer not to try to hand crank it backwards.i dont mind rocking it till i feel resistance. so ive been soaking the cylinders.with oil..I was actually going to try to make a hand crank this week, so I could try and get a few forward rotations going before i hit her with the starter, at this point all ill do is smoke the brushes in the starter by trying that
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Old 25-10-2015, 03:35   #13
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re: Replacement Engine for Volvo MD3B

would this be a good replacement? I talked to the guy and he swears its new or rebuilt, says the ports etc are spotless....and looks like its not been run ............... 15hp yanmar and the transmission is included....I figured it would get me back moving and I could go ahead and pull and overhaul the volvo somewhere clean , Like in my shop on a bench. and repaint it..and either save it for a spare or put it back in and save the yanmar for a spare or another boat
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Old 25-10-2015, 05:04   #14
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Re: Replacement Engine for Volvo MD3B

and yes I may be interested in the crank. but shipping it may be kind of prohibitive. May I ask you for a few pictures? I was thinking of notching a socket and welding it to a old boat winch crank to serve as one,,,,
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Old 25-10-2015, 09:58   #15
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Re: Replacement Engine for Volvo MD3B

One problem you may encounter if you want to go with yanmar.
I believe your volvo transmission has a 7 degree downward offset while the yanmar is a straight output. it means having to manufacture wedges to compensate for it
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