Metal pieces behind prop

[Paulj128]

I have a 1975 Evinrude 135 Strangler. Last year I found a bolt stuck in propeller. A little while later I found some good sized pieces of aluminum in hub and propeller. Despite this the engine ran real strong with exception of a bad idle and stalling when returning to dock(quite embarassing!)I figured, sooner or later the engine would show me what was the problem. The last time out the motor dropped to about 1800 rpm and would bog out if you didn't let off the throttle. Now the engine won't go past 1800 rpm. Where should I start to look? <br /><br />Thanks for any help in advance!

 

[DJ]

Re: Metal pieces behind prop

Paul,<br /><br />Run a compression check on all four cylinders. <br /><br />Let us know.

 

[Paulj128]

Re: Metal pieces behind prop

Ok, I ran compression test.<br /><br />Cold 1-128 <br /> 2-128 <br /> 3-115<br /> 4-121<br />Warm 1-121<br /> 2-125<br /> 3-101<br /> 4-125<br /><br />Why so much variation in #3 from cold to warm?<br /><br />While I had the cover off the motor, I removed the outer and inner exhaust covers. I discovered the source of the metal. Apparently the exhaust manifold? for 1&3 came loose and has been self destructing! What was left was flopping around so much the remaining bolt hole(1 of 3) is all ovaled and mushroomed. Fortunately the mating surface of block looks perfect. <br /><br />New questions, <br />1. Where to get a new part?<br />2. Should I replace thermostats while exhaust <br /> cover is out of the way? <br />3. Should I replace head gasket(s) and check <br /> compression again?(I had previously noticed <br /> water droplets on spark plug #3) <br /><br />I appreciate your experienced input!

 

[The Marine Doctor]

Re: Metal pieces behind prop

Pull the head of the lower compression side. Inspect the cylinder and piston.<br /><br />TMD

 

[Dhadley]

Re: Metal pieces behind prop

Those are the exhaust deflectors. Dont worry about them. Take out the remaining pieces. They are melting from high combustion temps. The most likely source is lugging the motor -- most often refered to as "overpropping". I would bet your top rpm is in the low 5K range, right? Lots of carbon in the exhaust area?<br /><br />Make sure you are using Champion plugs, good oil and 87 octane.<br /><br />Good luck!

 

[Paulj128]

Re: Metal pieces behind prop

Thanks for the replies. Doc, I will pull head tomorrow and I will let know what I find. Dhadley, you say the piece in question is an exhaust deflector. Does that "tune" the exhaust for HP? Who might have one? My local boat stores don't even know what the piece is! And yes, I have been running around 5k top out and using premium gas. Guess that's a no-no. Thanks again for the info, I'll let you know when I am ready for the dipsy divers again!!!

 

[Dhadley]

Re: Metal pieces behind prop

Like I say -- dont worry about replacing it. To do it "by the book" you have to have the motor apart and mill the exhaust blocks to fit. The last time I looked they were about 100.00 for the part alone. <br /><br />After you get the head off let us know what it looks like. Hopefully you dont have any broken rings from coking damage. If all looks good inside replace the 4 rubber deflectors while you have the heads off.<br /><br />Good luck!

 

[Paulj128]

Re: Metal pieces behind prop

I removed the head. The inside of cylinders, pistons and head look like brand new, no ridge at top of stroke, no scoring and no carbon in head. But, the head gasket was blown and leaking into the water passages. It was the original gasket as it has white factory paint on the edges. Is this just wear and tear, or an indication of some underlying problem? I will check the heads for flatness and if all is well, will reassmble. <br />I can almost taste them lakers now!