low rpms volvo md7a

[Ben Thomas]

One thing leads to another. problem solved leads to next question.

I have the volvo md7a (1982) after talking to other folks with more experience with this engine. they were telling me that it runs nicely at 2400-2600 rpms. mine on the other hand tops out at 2000 rpms. with a lot of heavy black exhaust at lower rpms. tends to ease off at 2000 rpms. air cleaner is very clean, no obstruction of passage or filter, my next quess is the injectors, but a mechanic mentioned it may be an oversized prop. now, I don't really know the actual size of it, I never thought to measure it when it was on the hard.
what size is standard prop on 82 30' cutter?
will haul out in two weeks for new rigging and mast work so thats the time to replace it with the cutlass if needed. It also could be the injectors malfunctioning more obvious at lower rpms blowing fuel in to rich of mixture. don't know. any opinions?? thanks ben




btlandscapers@imagina.com

[Larry DeMers]

Ben,

My vote is the prop is too aggressive. You should be able to maintain 2200-2400 rpm without too much trouble, and have a speed somewhere in the 5.5-6.3 range (from my incredibly precise memory of last summer ;^) ). My top end is at 2600 r's exactly.

Larry DeMers
s/v DeLaMer
Cape Dory 30

One thing leads to another. problem solved leads to next question.

I have the volvo md7a (1982) after talking to other folks with more experience with this engine. they were telling me that it runs nicely at 2400-2600 rpms. mine on the other hand tops out at 2000 rpms. with a lot of heavy black exhaust at lower rpms. tends to ease off at 2000 rpms. air cleaner is very clean, no obstruction of passage or filter, my next quess is the injectors, but a mechanic mentioned it may be an oversized prop. now, I don't really know the actual size of it, I never thought to measure it when it was on the hard.
what size is standard prop on 82 30' cutter?
will haul out in two weeks for new rigging and mast work so thats the time to replace it with the cutlass if needed. It also could be the injectors malfunctioning more obvious at lower rpms blowing fuel in to rich of mixture. don't know. any opinions?? thanks ben

demers@sgi.com

[Ken Cave]

Ben:

I am presently replacing my prop, shaft, and putting in a dripless
unit in my "new" Cape Dory 28.

The yard, Cap Sante Marina in Anacortes-found a three blade prop to fit my boat with a number of modifications. I did not realize that they make different props for sailboats verses motor yachts! The sail props are much thinner in diameter-thus my prop will be machined to match the old two bladed prop that came with the boat. Cost is about $325.00-but should be worth it!

Ken Cave
Cape Dory #227




bcave@whidbey.net

[Bob B.]

Overloading or clogged injectors are the usual problems associated with black smoke. Injectors are easily replaced. You should have a couple of spares aboard anyway. Overloading could be anything from a prop too large to a line or barnacles on the prop or shaft. One year, a trip with a knife below to scrape barnacles off of the prop cleared up the black smoke.

Check the fuel filters for trash and take a sample off of the bottom of your tank to check for items that could clog injectors. Do you treat your fuel? How often would you burn up a tank full? All of this could contribute to problems. When you change fuel filters, make sure that you clean the canister too.

I hope that all of this is some help. Aren't you glad that you have sails?

Bob



BundyR@aol.com