Puzzling features of the F38 engine

Engines, Drive trains, Propellers, Steering, Ground Tackle and other mechanical system

Puzzling features of the F38 engine

Postby Belanich » Sun Dec 13, 2015 10:00 pm

A couple of questions about my recently acquired F38 came to me today as I pretended it was spring (it was in the 60s today on Long Island) and sat in the lazerette staring at the the engine.

1. The engine not original. It is a 40 hp Yanmar (3JH3E). The geniuses that designed this engine placed the raw water pump facing aft! Also since the engine is bigger than the 27 hp there is absolutely no room on the port side where the pump is located. Does anyone have experience replacing this impeller?

2. Why is the engine not ventilated to the outside? The engine compartment is completely enclosed except for a small area open where the fuel line enter the engine compartment from the aft cabin.

3. I bought a Tides marine shaft seal from Paul Dennis to replace the leaking Syntron seal. Once installed there will be only about 1/2 inch clearance from the shaft coupling to the forward end of the Tides seal. Is this enough? Does anyone else have this type of seal?

Michael Belanich
s/v Dolcetto (Freedom 38 hull#65)
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Re: Puzzling features of the F38 engine

Postby F32Circle » Mon Dec 14, 2015 4:12 pm

We've been happy with the Tides Marine shaft seal in our F32. Only thing to remember is to "burp" the bellows when the boat goes in the water at first of the season. It will squeak if is running dry.
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Re: Puzzling features of the F38 engine

Postby Belanich » Mon Dec 14, 2015 5:04 pm

Hi Dale,
How much clearance to you have between the forward end of the shaft seal and the shaft coupler (in other words how much shaft is showing)? I haven't installed the new shaft yet but I calculate that I will only have about a half inch.

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s/v Dolcetto (Freedom 38 hull #65)
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Re: Puzzling features of the F38 engine

Postby GeoffSchultz » Tue Dec 15, 2015 6:49 am

Since this is a different engine than the boat was supplied with, I doubt that you'll get comments from other F38 owners, unless they repowered with the same engine.

However, my 40/40 utilizes a 3JH-2TBE, which has the same issues. The impeller replacement is a by-feel job. Get yourself a set of long arm 90 degree needle nose pliers and be prepared to curse a lot! I also got a Speed-Seal which utilizes knurled hear screws which are much easier to install blind than the standard ones.

-- Geoff
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Re: Puzzling features of the F38 engine

Postby bobr » Tue Dec 15, 2015 5:42 pm

Michael,

I plan on changing out the impeller on my 3GMF30 next spring. Rather than try to do it by feel I have thought about disconnecting it from the hoses and the belt and do it off the engine.

In your engine room, you may want to investigate installing a blower. Your engine will be happier with cool air.
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1995 Freedom 35 (Pedrick)
"Liberty"
Old Saybrook, CT
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Re: Puzzling features of the F38 engine

Postby sailmon » Fri Dec 18, 2015 3:57 pm

Standard impeller change procedure on our 3GM30F involves removal of the water pump from the engine. Once removed (takes no more than 5 minutes), we throw it on the Nav Desk and are able to change the impeller, in comfort, in about 5 minutes. Reinstallation is also quick and easy.
Sailmon (Captain Bob Allenick)
S/V Her Diamond
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Cleveland, OH
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Re: Puzzling features of the F38 engine

Postby Belanich » Sat Dec 19, 2015 8:57 am

When to the boat yesterday to take another look at the water pump to see if I can remove it from the engine. With a struggle I have access to the two top bolts. The only way I might have access to the bottom bolts is to remove the alternator. I hope I never have to change the impeller while at sea! The engine has 500 hours on it, is it possible that the impeller it was never changed? I am beginning to realize that the Yanmar 3JH3E should never have been installed in this boat! Also, when I was looking at the pump I started inspecting the engine mounts and noticed that one of the top bolts was missing and was lying next to the mount! That got me thinking about replacing the mounts since I am replacing the shaft. Any suggestions?
Thanks

Michael Belanich
s/v Dolcetto, Freedom 38 #65
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Re: Puzzling features of the F38 engine

Postby sailmon » Sat Dec 19, 2015 11:36 am

We have the standard 3GM30F on our 1991 F38 and have sometimes longed for a few additional horse power. Our boat easily goes to hull speed in flat water - but struggles going into strong headwind or waves in excess of 2'. Your issues/challenges are definitely an eye-opener when thinking about repowering.
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Re: Puzzling features of the F38 engine

Postby Mike Holibar » Sat Dec 19, 2015 8:24 pm

The lack of air supply to an engine is quite common and a result of bad practice. Having been in the engine business, we conducted commissioning tests which included measuring the air supply to the engine. Often we had to insist that extra holes were cut or a blower installed.

On Fyne Spirit, the engine was purchased two years before the boat was launched. It certainly supports the appearance that the boat was built around the engine. No pathway for air, and appaling service access. I am hopeing to pur the service access right in Malaysia by rebuilding the engine box completely. The other problem that comes for restricted air supply is the black stain that appears on the hull/transom in the area of the exhaust outlet. After any extended use of the engine we would have a sooty coating over the back of the boat. My first attempt, cutting in an engine room vent reduced the soot, but it was only the installation of a blower that fixed it completely. The soot of course comes from incomplete combustion due to lack of oxygen.

1/2 inch between coupling and seal seems quite close if you have flexible mounts, and the thrust is taken on the gearbox.

To Sailmon, 30 hp seems a bit on the low side for a 38 footer, but there are a couple of things to look at before going to repower.

Propeller efficiency is one. The bigger and slower a propeller is, the more efficient it will be. I had a 35 footer with a 30 hp engine. I changed the gear ratio to 3:1 and went to a larger prop and got consierable improved up wind motoring. There was of course a drag penalty when sailing. Prop size and speed is always a compromise.

I once had a thirty footer with a similar performance, very good in light airs, trotted along nicely, but could barely make any headway in strong winds. It had a severely over pitched propeller. When I set the propeller up correctly, it not only fixed the upwind problem, it substantially reduced fule consumption. Previously the engine was nearly always in a state of overload. Not good.

When over propped, the overload situation prevents the engine reaching full rpm which means it cannot develop its rated power. An over pitched prop can turn a 30hp rated engine into one that can only develop 15 hp, plenty for light airs, useless when real power is required. By carefully setting up engine,ratio and prop size to give maximum thrust, which will be bigger prop, bigger reduction, pitched to allow the engine to reach full rated rpm, the performance of a 30 hp engine can easily be as good as a 40 hp with a small fast prop. But there will be more drag from a sailing point of view.
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Re: Puzzling features of the F38 engine

Postby daletournier » Thu Dec 31, 2015 6:23 am

Hi Michael, I use a tides marine shaft seal on Freeform. Im guessing I have approx 3 inches between seal and coupling. I don't see 1 inch being a issue accept for there not being enough room to fit the spare seal carrier on the shaft. Having the spare seal on the shaft is a great option. My seal did leak at one stage due to me nicking it when I put the shaft back in after changing the cutlass. Being able to replace the seal in the water is a great option to have. Dale, its a tides marine seal you have, lip seal? I only ask because mine cant be burped as its a water injected lip seal.....do you have the water injected version. The PSS needs to be burped.
Also its important that the shaft is fairly free from scratches when using a lip seal, often the shaft is marked if you have been using Pss seal prior to a tides seal.
Cheers Dale.
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