8 HP Yanmar Overloading

[Howard]

I have a 1978 H-27 with an 8hp Yanmar. Over the past few years I've noticed a loss of power. The engine starts right up every time, no white smoke or black. I can't seem to get the RPMs up even at the beginning of the seasion and the engine seems to overload when I try to increase the RPMs and I start to get black dirty exhaust & blakc smoke. I don't think it's the blue cloud of burnt oil. My guess is I'm overlaoded? I doubt I got over 1000 RPMs on the way to the winter storage this year. Thank God for sails...but thant's what its all about... but always nice to know the iron genny is around for emergencies.I only use the motor for 30 minutes or so each time I go out since the my harbor has a very narrow entrence with no room to tack. On the return trip this year the prop and hull were a little fouled but not as bad as in the past and I'm beginning to think that there's a bigger problem than a fouled prop or bottom.I've been good about changing oil and filters but have never had any other engine work done. I wanted to know if you had any suggestions. I've heard that the mixing elbow often needs cleaning but am not sure what part they are refering to. The back of my motor where the exhaust pipes are doen't seem to match the shop manuals for the Yanmar.I'm on the hard now and have time to fiddle but don't want to make it worse.Anyone got any ideas?How about a recommendation for a professional to look at it?Thanks,Howard (Greenlawn/Huntington/Northport)

 

[Darrel]

Sluggish Motor

Howard, The problem as you describe it could be caused by all the things you mentioned.Coked up mixing elbow would be my first thought.Smoke and loss of power would be followed by the engine overheating if that is the problem.Fouled prop and dirty bottom. Please don't let your boat sit in the water all summer with out cleaning the bottom, shaft and prop. Those conditions really make your small motor have to work very hard to overcome. Not sure where you are located, but here in Southeast Florida we clean the underwater appendages at the very least once a month, and when looking for better performance before every race/day sail. Its just got to be part of the routine.Dirty fuel can also cause your problems. You can change fuel filters until your blue in the face. If whats in the tank is still dirty then it will make the motor run rough.So, you now have a long list of winter projects.Replace the mixing elbow, clean and paint the bottom, shaft and prop, and drain your fuel tank of fuel, clean the inside of your tank of all the crud thats in the bottom, polish the fuel, add Diesel stabilizer to the fuel you put back into the tank. Check the O-ring on the fuel deck fitting to be sure it is not dry and cracked. If it is replace it. (This can allow water to get into your fuel tank)If you work on all these items over the winter, I am sure that you'll like the improved performance of your boat in the spring. And don't forget, plan on cleaning the bottom, shaft and prop at least once a month while the boat is in the water.Good luck.

 

[Bill O'Donovan]

Mixing elbow, for sure

It may be inaccessible to remove, requiring you take the entire manifold off instead. There's stuff in the Archives on this, it's an every five-year project.

 

[Howard]

Thanks... mixer off and.........

Thanks for the comments...Didn't realize that I had the day off until I had that suit and tie on and my wife said...."OFFICE CLOSED..COME BACK TO BED". Well as long as I was up I went out the the boat (well took a little cuddle first). I'm on Long Island so the bottom growth isn't too bad but I do clean the bottom with a scrub brush at least once a year while in the water... AnywayI took out the 4 bolts that hold the exhaust manifold on and tool it off. TIhere wasn't a lot of crud inside near the exhaust port, only a verly little carbon powder. I can very easily blow through all of the holes. I'll clean the the rest out ... Do I need to replace it or just clean it up? I'll also drain the fuel out and clean the tank. In the past I've done this used new diesel. I've never polished (?)the fuel. It's only about 6 gallons so I bring it to the gas station and they recycle it with used oil. I've also herd that diesel is the same as #2 home heating oil (with the extra taxes added) so I've often though about putting it into my home oild tank. but not yet. I'll also replace the O-ring on the filler cap.The engine runs smooth (as smooth as a 1 cyl. engine can run). How about paying to have a compression check and possible replacing the injector? (Can you have it re-built?). Remember it starts easily... usucal on the 1st or second spin... I can also easily start it with the hand crank.. A little more work. Other suggestion?

 

[patrick]

I would still check the exhaust system

If you use the engine so little that is the most likely cause of the problem. You need to run a diesel engine hard enough to get hot and blow out the crud. I am not sure if you did verify that the exhaust was clear or not. You might try a temporary exhaust to see if this is actually the problem or not.