Engine smoking, and leaking intake manifold

[rtmt91]

1987, 260hp merc, alpha one

This is my second season with this boat and when I took it out for the first time this season I noticed a little smoke coming from the exhaust while at idle. It never smoked last season. I ran it about ten miles, so the fogging oil should have burnt off by then. Other than the smoking it seemed to run fine. I took it home and ran it on muffs the next weekend and after a few minutes it started smoking again. I does not do it at start up, it only seems to do it after the engine warms up. Temp gauge reads between 120?-140?. I put a can of restore in the oil, a mechanic told me he has seen some people have good luck with it. I also put two cans of seafoam in the gas. (I figured it wouldn?t hurt)

So this past weekend I noticed smoke again while sitting at idle. It also seems to have lost some top end speed compared to a few weeks ago, and when I am running at about 3000-3500 rpm and push the throttle hard it has a bit of hesitation, I did not see this the first weekend I had it out.
I could usually run about 4200-4500rpm and would show close to 49mph on the speedo. But this time it seemed to push really hard to get to 45mph at the same rpm. All that could be in my head too since I am more aware and looking and listening for anything. Also the oil pressure gauge started to bounces from 20-40 pretty erratic.

One problem I know I have is that I have oil leaking onto the top of the intake manifold. I tried to tighten the intake manifold bolts but I couldn?t get a good angle on them without removing the carb, so I didn?t. I had this issue last season but forgot about it when I had it winterized.

Could the leaking intake manifold be causing any of my problems?
Could the seafoam dislodged some debris and clogged up the fuel filter. I was told there is a small filter right at the carb at the fuel line connection is that so?
Could the type of oil used be a factor? I had a local merc shop change the oil and I am sure they probably used merc oil. They seem to always want to use genuine merc parts.


Last season before I purchased the boat the broker/dealer said they put a rebuild kit on the carb.
Like I said it ran great last year.

One more thing on the intake the leak used to show up towards the front of the motor now it showing up towards the middle to back.

Thanks for any info.

 

[Windykid]

Re: Engine smoking, and leaking intake manifold

Your intake manifold should not leak oil. It is probably leaking from the valve cover to the manifold. As for the rest you need to perform a compression test first and post the numbers.

 

[rtmt91]

Re: Engine smoking, and leaking intake manifold

Is the intakes similar to automotive type. I have had two vehicles that needed gaskets replaced in the past due to oil leaking and both were chevy 350's.

 

[RubberFrog]

Re: Engine smoking, and leaking intake manifold

Fix all the known problems before you try to diagnose the new ones.

 

[Reel Poor]

Re: Engine smoking, and leaking intake manifold

Also check the crankcase ventilation system. Make sure someone has not replaced the fittings in the valve cover with PCV valves. If PCV valves have been installed the engine cannot breath.

 

[Limited-Time]

Re: Engine smoking, and leaking intake manifold

A compression test, on all 8 cylinders will give you a good indication of the general health of your engine.
Another indicator is the color of the smoke, blue indicates burning oil, (mechanical seal break down) bad rings, or valve guide seals, black an over rich condition (fuel delivery system), white or steam indicates a cooling system leak into the combustion chambers, again a mechanical seal issue.

 

[rtmt91]

Re: Engine smoking, and leaking intake manifold

The color seems to be white kinda like steam.
Could a leaking intake do this. Or Should I look to the exhaust manifolds.
The engine oil does not appear to have water in it.

 

[Cptkid570]

Re: Engine smoking, and leaking intake manifold

You said that you can't tighten your manifold bolts because the carb is in the way.. are you sure you can't tighten them with a wrench (not a socket)

 

[Limited-Time]

Re: Engine smoking, and leaking intake manifold

If the intake manifold is leaking you have a bad gasket. It's not likely re-torquing will cure the problem..........but you can try. Just don't over do it and warp the manifold. Sounds to me like a head gasket, I'd do the compression check to either confirm or rule out that possibility,and go from there.