Oil or fuelin exhaust Raw Water

[Capt Paul]

Hello all,

I posted this on Boat Diesel.com but thought I would also ask here.

I just had my entire cooling system overhauled. The hose to the intercooler was blowing off and there was some blockage causing it. Anyway, long story short. I take the boat out a couple of times and after being out on the water a couple of hours I put the boat in the slip and see an oil slick coming out of the exhaust (when warmed up , I usually do not see anything, other then water).

I’ve talked to my mechanic and he will be on the boat tomorrow to see what it could be. He tells me there are too many places that it could come from and maybe a chemical analysis of the oil slick needs to be made to determine what type of oil it can be. This will obviously save him for backing out everything he put in to check proper alignment and sealing.

Other then the cooling system is there anything else that could be causing this??

Any info or shared experience very much appreciated!

[chiefrcd]

Paul,
Are we talking a "lot" of oil slick or a slight sheen on the water. I asked because I always have a slight sheen around the exhaust. I have seen that with other vessels as well. I've always attributed it to excessive fuel from some point, either the engine being cool or a posible injector issue. I will say that I switched to using ValveTech fuel last year and two things happend right away. The black soot that I use to suffer with is completely gone and the sheen on the water was greatly reduced. I think before I did a complete pull apart, I'd get the injectors checked and cleaned to make sure you're not getting excessive fuel through the engine and also make sure you're running hot enough.

[Capt Paul]

Cheif,

I had the same light sheen until the engine warmed up. This is much more substancial and it is happening after the engine is up to temperature. I did notice that the temperature guage is running a few degress cooler (expected, since the cooling system was clogging up) but I'm thinking you meant the fuel temeprature, correct?

I'll have him check the injectors, it just seems strange that this happened right after he did his work on the cooling system.

Valvetech sounds interesting, is it a fuel additive?

Thanks !

Paul

[chiefrcd]

Yes, engine temp was what I was refering to. I read your post over at boatdiesel.com and I would imagine that getting the mechanice to check it over would be the very best advice. Sounds like maybe there is something to the fact that all that work was done and then you had this issue.

Valvetech is a fuel brand that is avaliable here on the east coast. I'm not sure if they are nation wide. I know little about what all is added or why it's different but my limited understanding is that the fuel is fortified with the appropriate additives and cetane by the refiner and you don't have to add any additives yourself. I'm not sure what all they add, but the results seems, at least for me to be a much cleaner burn and a boost in top speed. I use to add cetane boost and a algecide (sp?) with limited success, since switching to valvetech fuel, I don't add anything and have had a boost in performance and I sure don't miss scrubbing that soot off the side of my boat.

[Mariner]

It could just be some fuel or oil that made its way into the exhaust system while the repairs were made. Give it some time. If it persists, then I would become concerned.

[Capt Paul]

Well my mechanic and I went out on a run on Antoinette to see what the source of the oily substance is/was. Once the engine warmed up he asked me to take it up to WOT. We did and the engine purred!!! My tack was about 150 RPM low so that needs to be checked for accuracy before we do anything with the prop. Anyway after a short run we drifted and monitored the exhaust. Not a trace. Took the boat back to the slip and needed to run the last 3/4 of a mile or so at about 6 kts do to wake restrictions. Back at the slip a little bit of sheen on the water but nothing like it was a couple of weeks ago. So no issue for know. I will keep on monitoring it.

Story doesn’t end here though. While we were up at WOT he opened up the engine cover and looked around. Raw water pump is leaking.. But wait there is more! Back at the dock he removes the pump to inspect the bearings and the seals. While doing so more water winds up in the bilge and starts accumulating on the low point just forward of the helm. I take a look and gasp... I see red in the bilge water.. Sure enough diesel fuel.

We look around the main tank and it has signs of fuel all around it. He Quickly determines that it is coming from the top of the tank. He says let’s pop the back deck off and see what going on. I gasp again.

Anyway it came off allot easier then I expected it to do. And sure enough the inspection port cover and the fuel fill/return and sender cover are leaking around the bolts and gasket seem. Look in the picture section for some photos if you have never had the back deck off. At some point you may need to do this. Some of the bolts were loose, vibration does its job. Anyway hopefully tomorrow it will all be back together again as the Queen Mary II is coming into San Francisco on Sunday and I hope to be on the water when it does!

[Mariner]

Well, it looks like you found the source of your sheen. It was probably getting shipped over the side by the bilge pump and simply appeared to be pooling near the exhaust.

You're lucky though, those sound like cheap and easy repairs. I check the bilge regularly. If something's leaking, it's going to turn up there. Anything abnormal in the bilge should be an indication something is wrong.