Visable smoke smelling like burnt rubber in engine compartment but engine temp normal

I own a 1997 Coyote Aztec water ski boat that has a inboard PCM Engine Model PLP in it, 351/5.8, 285hp, Holley 4V Carb, Ford based engine. The last time I took it out I noticed it sounded different when in gear like a subtle thump every few seconds I went against my better judgment and decided to still take it out on the water. About 20 minutes later after hauling butt up the river I noticed a smoky smell and cut my engine and lifted up the engine cover and saw some smoke that quickly disappeared. My temp gauge was not running hot. I took it out again with my auto mechanic friend Dan yesterday and the noise I heard was different this time and seemed to squeak near where you repack the shaft but was not taking on water. The burnt rubber smoke appeared again and the engine temp was running normal. Dan previously replaced the inline check valve from a plastic one to a copper one (from home depot parts) with a flap rather than spring with check ball and the fuel pump. I?ve owned the boat since 2006 and Dan has been the only one to work on it for cheap labor since he?s an auto not boat mechanic. Any advice on where to start would be great. This is my first time ever using one of these forums so I hope I posted in the correct area. Thanks! -Alisha from Sacramento.

Re: Visable smoke smelling like burnt rubber in engine compartment but engine temp no

The burnt rubber smoke appeared again and the engine temp was running normal.

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Where is the smoke coming from? I bet that would be a hint as to what was causing it.

An auto mechanic may be ok for preventive maintenance, and it doesn't sound like you do any of your own work, so maybe you need a marine mechanic to find your problem.

Since you have a PCM engine, not a Mercruiser I moved this over to the "Other Brands of I/O & Inboard Engines & Outdrives" forum.

Re: Visable smoke smelling like burnt rubber in engine compartment but engine temp no

The smoke seems to be coming from the drive shaft seal area. It was repacked last season. That area is also where a squeaking noise is coming from. The noise isn?t constant.

Dan has rebuilt my carburetor, replaced my thermostat and it?s sending unit, impeller, spark plugs, fuel pump, wheel bearings, and belts. He?s also taught me to change my own oil and fuel filter as well as change the transmission fluid which I do when needed. The first time I took my boat to a boat mechanic I spent $300 and my issue was not fixed. I don?t have a lot of money to spend so that?s why I?m posting on this site for help.

Thanks Don!

Re: Visable smoke smelling like burnt rubber in engine compartment but engine temp no


Where smoke seems to be coming from.

Re: Visable smoke smelling like burnt rubber in engine compartment but engine temp no

Howdy,

Well, you have a couple of possibilities there. Both of those exhaust "pipes" might be smoking because of overheating.

You may have a failed or partially failed raw water pump that still flows enough water to cool the engine but not enough to cool the exhaust system.

Your raw water pump failure (or a previous failure) may have sent enough impeller fragments into your trans oil cooler, to reduce your overall cooling water flow.

Pretty much all the cooling water usually exits out your "wet" exhaust. if it's not enough, exhaust components will get hot enough to burn/smoke etc.

The other component might be the prop-shaft "stuffing box" if you have the "nut" too tight it might be getting hot. Make sure it's not too tight or it won't be pretty when it seizes.....

Cheers,


Rick

Re: Visable smoke smelling like burnt rubber in engine compartment but engine temp no

Thanks for the info Rick!

Could the exhaust pipes be overheating from a recent replacement of my inline check valve from a spring loaded one to a flap one?



Copper one is the new valve.

Or could a bent shaft cause the smoking? I don't know if my shaft is bent but the prop has a nice ding on it from hitting something in the river.

Re: Visable smoke smelling like burnt rubber in engine compartment but engine temp no

AJB79 said:

Thanks for the info Rick!

Could the exhaust pipes be overheating from a recent replacement of my inline check valve from a spring loaded one to a flap one?

View attachment 168595View attachment 168596

Copper one is the new valve.

Or could a bent shaft cause the smoking? I don't know if my shaft is bent but the prop has a nice ding on it from hitting something in the river.

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I doubt that "clapper" type check valve would restrict water flow much unless it's got some debris in it and is sticking etc...

Those "stuffing" boxes however can get pretty hot if the nut is too tight.

If your shaft was bent, you would probably have a pretty noticeable vibration.

Put your hand on the packing nut and see how warm it is. If it's hot to the touch, (too hot to touch) it's too tight.

Re: Visable smoke smelling like burnt rubber in engine compartment but engine temp no

Or could a bent shaft cause the smoking? I don't know if my shaft is bent but the prop has a nice ding on it from hitting something in the river.

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Yes...