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Over heat with smoke 1998 5.7 L

C

canal_cruiser

Member
I'm running a '98 5.7 mercruiser. Last year had alot of problems with props/hubs, finally upgraded to a SS prop. Went out last weekend had no problem with the prop, after about two miles noticed temp gage was climbing, engine started to sound funny, so I shut down. Opened the engine compartment and smoke was pouring out. Saw no flames but still hit it all with fire extinguisher to be sure. Had to be towed in as I didn't want to chance more damage. Suspect the impeller died, will replace this weekend, just wanted to ask what other issues should I be looking for after something like this happening. Any help is better than none. Thanks.
 
Re: Over heat with smoke

It may be your gimbal bearing or engine coupler. The only way to know for sure is to pull the engine. The coupler is what the drive shaft from the outdrive mates with at the back of the engine. The gimbal bearing is what the driveshaft passes through at the transom. Your impeller is down in the lower unit of the outdrive. You wouldn't see smoke from that in your engine compartment.
 
Re: Over heat with smoke

At this time pulling the engine is not an option. Don't have the needed equipment or experience. I can take a look to check the engine coupler for damage. It's buried deep but I got to it last year when I was trying to trouble shoot the prop problems. If you are right I may be in over my head.
 
Re: Over heat with smoke

you would see smoke if the rubber tube that connects the riser to the exhaust tube melted, that happens everyday.

Ok Ready to test it ?

The long hose that comes in from the transom goes where, to t-stat housing ?

Or to a heat exchanger? Ether way disconnect it at th t-stat or exchanger, put water to the drive start the boat and hold the hose straight up, should have 12 inch's shooting up do it for 3-4 seconds and shut off the motor.

Good water there then it's down further the problem, no good water coming out the hose it's the impeller.

You forgot to mention what drive, alpha the impeller is in the drive, bravo it's engine mounted.

Ok so say you replace the impeller cause it's bad, or the impeller is good cause of the hose test you got to figure whats clogged.

If the hose goes into a heat exchanger, then that could be clogged, or the t-stat is bad or frozen closed. So say you replace the t-stat cause it's bad or you find you have those dreaded little check balls and they stick all is good to the riser, then maybe the riser is clogged.

But be aware getting the rubber to melt on the risers, you also probably melted the shutters/ flappers clean off now that maybe clogging your exhaust.

Only way to know is pull the risers or with the drive off looking up the exhaust hole.

Say you find the impeller is toast and there is nothing left i wouldn't be surprised if you melted the whole water pump housing.

Do the test then work from there.

No matter what your in for a couple of day's work in the least.

May the force be with you .
 
Re: Over heat with smoke

chiefalen, Thanks for the advice. I think I'll try your tips before I spend money that I don't have to fix something that is not broke. Just don't want to spend another summer with the boat sittin' in the driveway.
 
Re: Over heat with smoke

Chiefalen, After starting to follow your advice I think I may have found the problem.The hose coming off the T stat to the exhaust manifold(I think, it's under the riser.) was fried at the manifold where the drain valve is.Couldn't see it befor cuz it was sitting close to where it should be(and poor troubleshooting on my part) So do I get away cheap and just replace the fitting or do I need to follow thru the system looking for more damage? The force is strong with you..:)
 
Re: Over heat with smoke

That sir maybe the whole problem, always when trouble shooting, a person changes one thing at a time, run the motor if it is fixed fine if not, then you move on to the next thing on the list.

Welcome aboard !
 
Re: Over heat with smoke

Thank you for your advice. I was incorrect when I said the HOSE was fried, it actually was the elbow connector( some type of plastic by the looks of it) melted to crap.. Parts shop opens Monday and I'll go from there. Sorry for the delay in response, internet has been down all day. Could not have gotten this far with out your help. Can not thank you enough!
 
Re: Over heat with smoke

Ok, I'll continue with your instructions after I replace the elbow fixture. Can't do that until Monday, but I'll see what I can check until then. Teach me o' wise one! And Thank you!
 
Re: Over heat with smoke

OK, Got the t-stat replaced, old one looked bad and stuck in the top of the housing, real fun to get out. I'll have to hold off on the rest of the troubleshooting until I get the elbow connector for the starboard side exhaust manifold. Don't want to replace the impeller until I do the checks that chiefalen suggested, such as water to outdrive, pull hose from outdrive that leads to T-stat housing and see if there's a 12 inch fountain. Then on to exhaust manifolds and risers. Anything else I can do until the parts arrive? Thanks to all who have given advice that so far has helped!!
 
Re: Over heat with smoke

your welcome, new t-stat new rubber that melted run the boat, one thing at a time.

Also happens to be the cheapest way why buy what you don't need.

But be aware if you had a flapper and it got hot enough to melt the rubber then it might have melted off the flapper.

Just wanted to make you aware.

Might want to pull the riser and peek down the tube i hate to tell people to do that alot of things can go wrong trying to remove a riser.
 
Re: Over heat with smoke

Ok, manifold exhaust elbow came in early, to much rain in delaware to install today. No garage (sucks for me)Question for all you experienced guys, why would my replacement part be made of metal while the original definitly appears to be some sort of high temp plastic? I know cuz plastics is what I do for a living..any ideas? I'm thinking they saw the error of their ways,Also I'm thinking I should replace both elbows with the metal replacment parts.. All good advice welcome! Thanks!
 
Re: Over heat with smoke

The t-stat could have been the problem right there. Mine went bad and i blew the u shaped hose to the circulating pump. That was fun, thank g-d the dog house was over the motor, steaming water all over the motor.
 
Re: Over heat with smoke

I'm pretty sure I got the right part. The merc dealer did the ordering and the instructions came showing install instructions for my engine etc. I'll install after work and see what happens!
 
Re: Over heat with smoke

Chiefalen, OK wrong part! after you stop laughing your butt off, could you tell me where I could get a parts listing for 5.7 liter? Apparently my merc dealer is as smart as me..I had the original part (although burnt ) with me and they didn't even bother to look at it. Just ordered from the computer. And I trusted them!I have the part number I need and will find out tomorrow (of course they are closed now) if I can return and probably re-order the correct part number..what would have been a couple hour job for you and other senior members is turning into a couple of weeks for me. I do learn from mistakes and this one won't get me again! Thanks for any help!
 
Re: Over heat with smoke

Guy, Thanks!I remember you from my prop problems last year! You're good! As are all of the senior members that make this a great site!
 
Re: Over heat with smoke

Hey i want to meet the man who never got the wrong part at least once.

Whats worse getting a part that is defective and you don;t find out till you spend a day putting something back together.

I feel your pain.
 
Re: Over heat with smoke

OK, Chief I hope you or other senior members are on today..I finally got the elbow to the the exhaust manifold installed. I had to take a tap and clean the threads out from the plastic fitting that burnt up. went to check if the impellor is working as previously instructed. I got nothing when I went to start, no click no nothing. the shifter won't let me go into neutral or reverse. Saw a previous thread that said maybe lower cable is shot?? I can get it to go into gear but obviously still no start since it should be in neutral to start, HELP I've already missed most of the season, I'd like to get her out at least a couple of times before I have to winterize!!
 
Re: Over heat with smoke

Chit ok remove the lower cable from the shift converter. See f the throttle will move. if yes then the lower is shot if not then remove the top one is if it moves, in other words figure out which cable went.
 
Re: Over heat with smoke

Thanks Chief, OK, I'll give it a try tomorrow. In my disgust, had a few beers and now won't be a smart time to try, I can see the throttle moving but only when I put it in gear??? wtf? I'll follow your instructions in the morning and see what happens. Can't thank you enough for the help.. starting to think boating is only for the rich, or mechanics who know them inside and out! Thanks again!
 
Re: Over heat with smoke

Naaa it's like a woman you got to hit them once a week if you don't know what they did they will.

Just kidding.
 
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