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engine power

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Joined: 08 Jun 2004
Posts: 5

PostPosted: Tue Jun 08, 2004 12:22 pm    Post subject: engine power Reply with quote

I am purchasing a 1988 Pearson 31. It comes with a 16 horsepower engine. Is a 16 horsepower engine strong enough to pull the boat at hull speed even in a chop?

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Joined: 26 Sep 2003
Posts: 16
Location: Lake Rathbun, Iowa

PostPosted: Tue Jun 08, 2004 2:35 pm    Post subject: 2GM20F Reply with quote

I only have about 3 months of P31-2 experience, but have not found it to be at all an issue. I have a Gori 2 bladed folder which probably is not as efficient as most props and have never felt underpowered. Granted, I'm on an inland lake and have no currents, but comfortably cruised into a 20 knot headwind with short choppy conditions with no problem. A similiar question was asked on the Pearson sailnet newsgroup regarding the 33-2 (uses same engine) and all the responses were that the boat is sufficiently powered (some of the responses were from areas that do deal with currents). The 2GM20 is also used in the Tartan 31, Irwin Citation 32, and C&C 33.

Congratulations on purchasing a great boat. I have found her to be well put together and fun to sail, haven't had a moment of regret.
Trevor Richards
s/v 'Cecilia', P31-2 #231
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Joined: 07 Jul 2003
Posts: 21

PostPosted: Wed Aug 25, 2004 5:51 pm    Post subject: Engine Power Reply with quote

I think you will find the 2gm20 adequate. I have a 1987 version and was very dissapointed with engine performance..engine wouldn't rev past 2800rpm, smoking etc. I changed the exhaust elbow and it was like I had a brand new engine! I can make 6-6.5 kts, essentially hull speed at 2800-3,000 rpm.

This is a common problem on older Yanmars and is relatively easy to replace. I an provide guidance if you find it's an issue
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PostPosted: Tue Sep 14, 2004 3:41 pm    Post subject: Reply with quote

Could you tell me more about the elbo replacement that made your enging run like new?

Lastr year I was having problems with unburnt fuel being blown out the exhaust. Over the winter we pulled the injectors and sure enough there was a bad spray pattern and they were retipped. Upon launch the transom sooted up upon starting the engine for the first time and I thought all was for not. After a few outiongs the exhaust seemed top clean itself up much to my relief. The mechanic said it would take a bit to clean out the residual deposits. Thered are still some problems, however.

There are two things that make me interested in your comments. Upon initial starting of the engine with the throttle fully engaged there is a momentary burst of black smoke and a little slick of what looks like unburnt fuel coming out the exhaust. This happens for a second or so and then the exsaust discharge looks normal (clear). If the engine is started later in the day it can be started at low throttle and there is not a problem. The engine starts without a problem every time and runs like a champ At @ 2300 rpm the back of the boat squats deeply into the water resulting in the transom becoming fouled by the exhaust discharge after a short time. This is driving me nuts and would like to correct the problem. I mentioned it to my mechanic and he thought that there may be some resistance in the exhaust causing the problem, thus I am interested in your suggestions/theory on what may causing the sooting. I notice this on many boats and wonder if it may be a fact of life when a boat squats under power.

Thanks in advance,

Pu'uhonua #193
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Joined: 07 Jul 2003
Posts: 21

PostPosted: Tue Sep 14, 2004 5:42 pm    Post subject: engine power Reply with quote

I have the same problem when starting cold. I have to give it nearly full throttle and get a big gout of black smoke, then it settles down and starts easily later in the day. I don't think it's anything to worry about, just a simple engine going on 20 years old, but you might want to post a query on a very good Yanmar discussion board at
http://yanmarhelp.com/msgboard. They seem to have a guy who is a professional mechanic that answers posts. Very helpful. Please let me know what you find out.

As to the stern squatting you didn't mention what spped you werre going when this happens. My understanding is that this is more a function of the boat reaching hull speed (I hit it about 6.5 kts) than the engine itself.

If its happening at a slower speed, say 4-5 kts I wonder if it is a trim issue.

The P-32 has a theoretical hull speed of 6-5 kts or so. Much faster ant it will start to do what you are seeing. If it's squatting i.e reaching hull speed at 2400 rpm, I'd say your engine is working pretty darn well.

Good luck.
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Joined: 18 Jun 2003
Posts: 31
Location: Westfield, NJ

PostPosted: Mon Sep 27, 2004 9:10 pm    Post subject: Reply with quote

One point to keep in mind is that the cruising rpm for the 2GM20 is around 3200 rpm. Ideally this is where the engine will run at hull speed. If you're hitting hull speed at 2300 rpm you may be overpropped. Running routinely at well below cruising rpm is actually not good for the engine. I went to the maker of my variable pitch prop, PYI, and gave them my boat and engine specs and they recommended the correct pitch. It seems to be working well.
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PostPosted: Wed Oct 06, 2004 11:59 am    Post subject: Reply with quote

Thanks for bringing the notion of being overpropped into the mix. When I bought the boat a couple of years ago there wes a three blade prop installed but there was also a two blade prop in the truckload of spare stuff which also came with the boat. Under certain conditions my wife has thought that the engine seemed to be straining a little (making more noise than appropriate for the speed and conditions). This seems to be less noticable at higher RPMs and I am thinkling that there is less strain turning the prop at higher rpms than at lower rpms when less power is needed. I will be checking this out during the seemingly endless Maine winter about to begin.
Thanks again.
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