Joel, that sounds Important and Potentially Dangerous to troubleshoot. If it indeed an exhaust leak, I would uncover the engine - engine off - and inspect visually for signs of the leak, as a first step. But one thing I surely would do before trying to troubleshoot with the engine running, would be to have a responsible observer standing by outside the boat who can monitor for safety, able to kill the engine and call 911 if necessary. Someone who would NOT come in after me until *after* they'd called for help.

Joel,

One specific point to check is the connection between the exhaust riser and the engine manifold at the flange. If the riser had not been really tightened into the flange, there could be blow by there.

Other places to check are the connections at the muffler, and if you haven't replaced the exhaust hose from the muffler to the transom, you should consider inspecting the hose.

Joel,

I will weigh in with the others here, exhaust leaks along with our 110 volt electical systems and propane system are the three systems with the most risk on our boats. Checking out this system is critical for your and your guests safety.

That said, there may be a simple cause for your odors. Check to make sure the crankcase vent is firmly up against the air filter on the engine. If it is just dumping the fumes in the engine compartment and not into the intake it can make for a lot of odor in the area. True exhaust system leaks usually show up pretty obviosly as you will note a lot of soot and exhaust stain in the area of the leak. The breather will put out a great deal of oily mist and the smell of burnt oil and some exhaust smell.

Steve
My crankcase breather has a hose that goes to the bottom of the engine I put a bottle under it to collect any oil,my engine is a 1990 25xp and it looks like it came from the factory this way. Are you saying I should reroute to run it into the air filter.

Bill, many skippers have done that, I do your bottle trick, been working for me for 15 years. Your boat, your choice. I'll let Steve comment further.

Bill,

I am not certain about any changes made to later installations, my boat is a 1988 with an 25XP installation. The breather does often emit an oil mist along with a great deal of vapor. My installation I think is typical, it has the breather hose from the valvel cover going to and lying against the foam air filter element. Some I know have modified there intake to put a hose barb on the intake manifold to connect this breather line to. This makes for a cleaner enginge compatment as at times oil that collects from the breather can drip off the foam filter. Some later air filter housings have the incorprated into the airbox.

As for your installation the jar on your boat, will collect oil emited from the breather but I will assume it is vented and will emit a lot of fumes that still will fill the engine compartment. I would bet a previous owner installed this.
I would think a tee from this jar with a hose to the intake would do a lot to eliminate fumes in the engine compartment as they would be fed back into the engine rather than just building up in the engine area. With the engine at RPM there is a significant blow by coming out this breather hose.

Hopefully other will speak up if my input is inacc.urate

I put the container a1 qt oil container for the hose to go into but I do like the idea of running a hose up to the breather and sealing the container . The oil stays in the jug and the fums go into the engine any one else with other ideas?

I've mentioned this before, but will repeat it, as I think it's important. I would not under any circumstances modify the engine so that the crankcase vent goes directly into the intake manifold, or even directly into the metal air filter housing (on engines that have one). Diesel engines are oil burning engines (diesel fuel is sometimes called diesel [I]oil[/I]). If for any reason a quantity of oil gets blown from the crankcase vent directly into the intake manifold, the engine could 'run away' and destroy itself. Pulling the fuel shutoff would not stop the engine as it would be running on the oil coming from the crankcase vent. Think about how little fuel your engine consumes, and you can see that it won't take much from the crankcase overflow to cause this to happen. If my engine had that modification, I'd remove it.

While you may consider this to be a small risk, I recall someone responding to my prior post on this topic: he'd personally seen a large diesel engine do just what I'm describing, so it can happen.

My M35A came from the factory with the crankcase vent run to the air intake and attached so the hose points in the same direction as the air intake (aft). Any fumes will be sucked into the intake, but oil would not.

Sorry for posting this again, but I feel it's important.

Gary,

I am quite aware of this issue, I purchased a core engine and rebuilt it that had experienced a run away. Your concern would warrant a sump jar or air oil separator between the crank case vent and air intake to reduce this risk but, the fumes should be routed back to the engine intake, it is a standard practice, at rpm all internal combustion engines produce a high volume of blow by, this is just pumped into the engine compartment and bilges if not routed to the intake.

Do you run bilge blowers any time your engine is running? This too will prevent fume build up, I do not but the engine compartment stays fresh smelling on my boat.

Yes, my crankcase vent terminates right by the engine intake so it sucks the fumes right back in. I've only ever had a couple of oil drips, and I always have sheets of oil absorbent cloth under and around the engine so they show up if it does drip (and gets absorbed). I do run the blower, but mainly to try to keep engine compartment temps down to keep the alternator happy; not sure it does anything, but makes me feel happy..!!!

Gary,

Sorry, I did not read your post closely enough. I was confusing yours with Bill's installation. A sump jar and tee sounds like set up that assures both fume return and preventing excess oil from getting back to the intake.

By the by the engine I purchased that experienced a run away had been over serviced with oil.

[QUOTE=Steve Frost;19011]By the by the engine I purchased that experienced a run away had been over serviced with oil.[/QUOTE]

I have been 'over served' at a bar, but never realized engines had the same problem. :rolleyes:

Bill-
I had a 1986 C30 with an M25. The exhaust riser (the part of the exhaust between the manifold flange and muffler) was wrapped in fiberglass tape insulation a good 3/4 thick (at least I hope it was fiberglass and not asbestos). The insulation looked fine upon quick inspection, but we too had fumes going into the cabin and cockpit. Upon further study, the top of the wrapped pipe ( in a difficult to see the spot) had exhaust blowing out of it. Not a lot of discoloration around and not a large hole it. With a mask, I removed all the insulation and found that pretty much the entire riser had disintegrated beneath the wrap- just rusty debris left and the wrap was the only tube that had been directing the exhaust flow.I had to remove the manifold flange and replace (with new gasket) and rebuild the riser from black pipe elbows and straight sections purchased from the hardware store. The bronze water injection tube was in great shape near the muffler. The C30, at least for my year, used black pipe for the riser. With your similar engine and vintage 36, this might help.

Paul

Duane,

When you were over served, did you run wildly out of control and smoke heavily?

Steve

[QUOTE=Steve Frost;19021]Duane,

When you were over served, did you run wildly out of control and smoke heavily?

Steve[/QUOTE]

I was over served by a friends wife who didn't know the difference between Bicardi's dark rum and Bicardi's 151....:eek: I definitely didn't RUN, but I was certainly out of control, spinning at ever increasing RPMs :cool: (so was everyone else.!) And I wouldn't start the next morning.