Opinions on Sea Foam Use In Diesels

[robertsapp]

I asked this question in Ask All Sailors but didn't get much of a response, so I'm posting it here. I was hoping to get some feedback from people who had actually tried this, or had good reasons why it wouldn't be a good idea. Information on the Sea Foam website says to fill your fuel filter bowl with Sea Foam and run it through your diesel to decarbonize the cylinders, free stuck rings, and clean the injectors. I'm tempted to try it, but I'm curious if anyone out there has done it and/or has any advice on the subject. I've used it in my cars and gas powered boat for years, but never thought to put it in my diesel tank or use it straight as a decarbonizer.

 

[Steve Dion]

I really do not think that this is necessary to decarbonize the cylinders if you run the boat at the recommended 70-80% of the max rated RPM.

On the other hand if you have been running your engine at lower RPM's and there is a problem it may be worth trying.

 

[robertsapp]

The previous owner of the boat, who owned it for 15 years, ran the engine at about 1500 rpm rather than deal with an alignment issue that causes a significant vibration at higher rpms. Although the engine starts easily and runs smoothly, I know there is a significant carbon buildup issue as I had to put a new exhaust elbow on the boat within six months of buying it - it was completely plugged up. Lately, I've had a knock from the number one cylinder that doesn't appear to be speed dependent, and one of the many things that can cause such a noise is a carboned up injector that sprays late and/or produces a poor spray pattern. So I'm interested in giving the decarbonizing a try, particularly since I'm familiar with Sea Foam and it's always seemed to work well, but I'm a bit concerned about putting anything through my diesel that might cause a problem.

 

[Steve Dion]

Robert: I would pull the injectors and take them to a shop to have them checked out. Then you can deal with the alignment issue. I doubt that you are going to have much of an issue with using this additive in the proper amount.

I also doubt that it is going to completely take care of the carbon build up with a single treatment.

I think running this engine at 3000 - 3200 rpms for an hour or two at a time is going to do more good than any additive. These engines are very robust. Obviously you do not want to over heat it, but common sense will prevail.

I would contact the Yanmar Distributor in your area for additional advise. Especially if you have any doubts.

 

[robertsapp]

Thanks Steve. I'm pretty sure the previous owner must have wrapped a line around the prop or something, because I've moved my front motor mounts as far to port as they can go, and I still have a .008 to .01 gap on the port side of the coupling that I just can't close. I suspect a bent strut, and I intend to address it at my next haul out, along with getting the shaft checked for straightness and balancing the prop. In the meantime, I really can't run the engine as hard as I'd like, because I'm concerned about damaging the transmission due to the vibration. As for the sea foam, I feel very confident that adding it to the fuel will be fine, but I was concerned about following their recommendation to fill the filter bowl with it, which means the engine would be running on 100% sea foam for ten minutes or so. The stuff is an amazing cleaner though. A dirty little secret is that's all an induction system cleaning for your car amounts to. Remove the brake booster line, and pour a can of sea foam into the vacuum line to be sucked into the intake manifold while the engine runs to clean the carbon and crud out of the top end. A mechanic will charge you $189 for an induction system cleaning, but it's really only ten minutes work and an $8 can of sea foam.

I haven't worked up the nerve yet to pull the injectors - I need to dive into the service manual again and make sure I know the potential rocks and shoals for a job like that.