Black residue on swim platform

[gregpallen]

I am getting black residue on the swim platform on my 290. I purchased the boat last fall so I have not had a lot of experience. I believe it has been doing this since I owned it. In the past I was able to clean it off fairly easily with soap and water but yesterday it seemed a bit more stuborn. It seemed perhaps it was a little oily. I only have 250 hrs on the Yanmar 18hp and the engine runs fine. I did install a max prop last winter according to the manufacturer's instructions based on engine model and gear reduction and I was wondering if it might be over propped causing incomplete combustion. The engine runs at about 3200 RPM wide open and I normally cruise at approx 2300 rpm. Anyway, if any of you experienced sailors have had this issue I would love to hear from you. I am not sure if it is something to be concerned about aside from the inconvenience.

Greg

 

[Bill Roosa]

Well not to put too fine an edge on it, its a diesel, they do this.

 

[seadaddler]

My 290

Sorry to say my 2001 290 did the same thing but a year or two after owning it I had to clean out the mixing elbo and it did help and the boat did run much better than new or just seemed like it ran so good after cleaning the bottom hull cleaning the 2 blade prop and cleaning the mixing elbo which was very clogged up with soot so any way it performed so much better and less soot on the stern for sure.
Nick

 

[bigsick]

Black soot on swim

Sorry to say my 2001 290 did the same thing but a year or two after owning it I had to clean out the mixing elbo and it did help and the boat did run much better than new or just seemed like it ran so good after cleaning the bottom hull cleaning the 2 blade prop and cleaning the mixing elbo which was very clogged up with soot so any way it performed so much better and less soot on the stern for sure.
Nick

I have the same problem with my 326. I thought it was residue from the diesel. Want to try to clean out mixing elbo, what ever that is. I have a fresh water 2GM20F, does it have a mixing elbo.

 

[Steve Dion]

Greg:

I would think the prop may be your problem. You have probably read that the tach on the Yanmars are normally off by a few hundred RPMS. I would get your tach checked out and then persue the pitch on the prop.

The normal cruise speed on these engines should be about 2600-3000 rpms, but the engine should also rev to approx. 3600 at WOT.

Can this prop be adjusted in the water? If so I would think that 1-2 deg less pitch may fit the bill.

I would suggest that you clean the sooty area and give it a good coat of wax to make future cleaning a little easier.

 

[seadaddler]

Yes

Yes you have a mixing elbo but if you are not handy with tools and know some mechanical engine back ground it is not easy taking the mixing elbo 2 parts apart to get at where it needs to be cleaned and cleaning with a pick or any pointed tool is not very easy,need a good plumbers tools to take apart.
The black sooot could be from a few different things,my engine did become hard starting in cold tempertures and in the spring was very hard starting and that's when I removed the mixing elbo and the engine started up in a second so that's when I checked the mixing elbo and after very hard work took it apart to see all the buildup and very small hole,I used ice pick and many sharp pointed tools to clear the hole to normal size and with clean hull and clean prop with cleaned mixing elbo the boat reached hull speed with less rpm's and less soot.
Nick

 

[gregpallen]

Thanks all for your comments. I think I will take a shot at the mixing elbow just because the boat is 10 years old and I dont know if anyone has ever looked at it. May be worth just replacing it. The prop is a three blade max prop but its the classic so I would probably wait till haul out to adjust pitch if it needs it. I will double check the WOT rpm to see where I am with that. I also now have another theory and that is that I ran the engine last weekend without the thermostat. (I removed it to trouble shoot an over temp problem which turned out to be a bad impellar). I am now thinking that the engine is running too cool to efficiently complete combustion...thus increased carbon out the exhaust. I have a new thermostat and will intall it this weekend.

Greg

 

[Steve Dion]

Greg:

It is a good idea to check the elbow. I do not think that the coaking problem is as much of a problem in fresh water as in salt water, but it is a good idea to check it out regardless.

I would not purchase one until you do your inspection. When you remount it be sure to use never sieze on the bolts and threads. This is NOT an easy job so be prepared. Depending on you access it can be very time consuming. Be sure to order an exhaust gasket before you start, you should replace the gasket even if the elbow is okay.

When you take the unit apart, you sometimes need to have large pipe wrenchs and a torch to break the parts apart.

Please let us know your outcome.

 

[gregpallen]

Greg:

It is a good idea to check the elbow. I do not think that the coaking problem is as much of a problem in fresh water as in salt water, but it is a good idea to check it out regardless.

I would not purchase one until you do your inspection. When you remount it be sure to use never sieze on the bolts and threads. This is NOT an easy job so be prepared. Depending on you access it can be very time consuming. Be sure to order an exhaust gasket before you start, you should replace the gasket even if the elbow is okay.

When you take the unit apart, you sometimes need to have large pipe wrenchs and a torch to break the parts apart.

Please let us know your outcome.

Thanks Steve, I'll give it a go and let you know what I find

Greg

 

[seadaddler]

Easy

If I remember plenty room getting off but 10 years spray WD-40 or something so the 4 bolts don'tive you a problem and come off or the studs may come out,the problem will be getting the mixing elbo apart and the threads are reverse threads if I remember,I think I added some heat and good big vice and big wrenches and that is the hard part.
If it does not come apart maybe bring it to a shop to help take apart,I used ice pick type tools slowly chipping away at the passage and hope yours is in good shape and not need to be replaced.
Nick

 

[jmhoffman]

Greg,
I also have the same issue on my 290 with about the same engine hours as yours - just noticed it this year. Looks like I will be looking at the mixing elbow as well.
Jeff

 

[Dellcom]

The soot problem can be corrected by adding a sulfur additive to the fuel. The engines were designed to be used with high sulfur content, today, the fuel is ultra ultra low sulfur content. The additive can be found at the local auto parts store...choose the one that makes sense to you.

 

[Nelsonhow]

When I had to replace the mixing elbow on my 1 GM I removed the elbow from the engine and then had to separate the mixing elbow from the engine fitting. PB blaster and a propane plumbers torch were not successful. I took it to a muffler shop and tipped the worker $10 bucks. He put the elbow in a vice on the bench and used an acetylene torch to heat it cherry red. The parts came right apart.

 

[Steve Dion]

Greg:

We just used Totally Awesome on the stern of a boat. Carbon is gone with the wipe of a rag. Same thing on a stern fender. Spray on and wipe off the crap. At a buck a bottle you cannot beat it.

 

[jmhoffman]

Greg, did replacing or cleaning out the mixing valve resolve this issue? Can someone explain to me why a restricted mixing valve would cause this condition (soot on swim platform)? Thanks, Jeff

 

[TR6]

It chokes the exhaust flow. I had my old elbow hot tanked at a rad shop and it lasted 2 years before needing re doing. I decided to put a new one in and no more issues...... On the oplder 31's it's not a bad job, 30 mins max !