Exhaust noise coming out from under cowl

[15hpevinrude]

So I had a full week on the lake with my 1996 Johnson 35HP motor. Ran great, starts first try every time, idles nice, until the last day. I had three people in my 14foot boat( 2 of which are "Heavy") it was working pretty hard, and having trouble plaining with all the weight in the boat, I heard a "pop" sound and the motor got really loud and died. I managed to get it re-started and it sounded like exhaust noise coming from under the cowl cover. I pulled it off and it was very loud. I could get it running but when I tried to put it in gear it would die. Tried this 4 or 5 times and the boat moved maybe 20 ft, to the point that it wouldn't start any more. I got towed back to the dock, which prob. took most of an hour, when I got there the engine had cooled, and would start and drive, but had the very loud exh. sound, and no power, I am thinking the tube that transfers the exh. to the prop. came off, or blew a gasket, or something like that. I don't know what exactly is under the powerhead, if there is a gasket, or "o"ring or what. Does anyone have any thoughts as to what this may be, and how hard is it to fix?
Thanks

 

[nwcove]

Re: Exhaust noise coming out from under cowl

check the exhaust plate....it may have blown that gasket? with the engine running on muffs or in a barrel, you should be able to feel the blow by around the plate....if thats what it is.

 

[15hpevinrude]

Re: Exhaust noise coming out from under cowl

I assume you mean the plate on the side of the motor? It kind of sounds like its coming from under the powerhead, but the exh. plate should be easy enough to rule out. I'll have to try that

 

[Daviet]

Re: Exhaust noise coming out from under cowl

Check the base gasket, #8 below, it sounds like it blew on you. You didn't list a model number, so I just grabbed the first one.
http://www.ishopmarine.com/ishop/js...cCatFilter=BRP&eCatSupFldr=supplier-100-005-E

 

[15hpevinrude]

Re: Exhaust noise coming out from under cowl

Thanks, It sounds to me it might be something like that. I assume I would have to dissassemble and remove the whole powerhead to get to that? there is alot going on under that hood, not as simple as my 1980 35hp motor

 

[Daviet]

Re: Exhaust noise coming out from under cowl

Yes, the power head will have to come off. You can locate the leak by running it on a hose and squirting some oil into the carb and look for smoke coming out between the block and the midsection.

 

[mr rookie]

Re: Exhaust noise coming out from under cowl

hey guys how do i start a thread is there a wait when u first sighn up?

 

[Daviet]

Re: Exhaust noise coming out from under cowl

Go to the first page and look in the upper left side, there is a blue block that you click on that says, Post A New Thread.

 

[mr rookie]

Re: Exhaust noise coming out from under cowl

dont have that

 

[Daviet]

Re: Exhaust noise coming out from under cowl

Here you go, look for the blue box on the upper left.
http://forums.iboats.com/forumdisplay.php?f=24

 

[15hpevinrude]

Re: Exhaust noise coming out from under cowl

So I finally got around to checking to verify if the base gasket was leaking. I was going to start the motor and spray oil in the cyl. to see if there was smoke coming out from the bottom of the power head. I put the muffs on, went to start it, and I did see a puff of smoke, but it didn't come from where I thought it might. It came out of this HOLE in my crankcase!

View attachment 110725View attachment 110726


Now I am really confused, The motor still runs, and doesn't sound bad, aside from a loud exhaust sound coming from it. You can see the hole in the crankcase, but the connecting rod is still intact, and there doesn't appear to be any dammage inside. It turns over by hand freely, and I can turn it over and look inside the hole and see the piston /connecting rod moving back and forth. It doesn't appear to be broken? The rod bolts are both there and intact. Where did this hole come from?. I do notice the rod swings very close to the case, Is it possible that when I was driving(and the boat was very heavily weighted down, and was having trouble getting on a plane) the stress caused the crank to deflect a bit and kiss the case, without breaking anything?

 

[slag]

Re: Exhaust noise coming out from under cowl

Holy Schnikes!!!

Tried duct tape yet?

 

[15hpevinrude]

Re: Exhaust noise coming out from under cowl

Are you actually being serious? Because someone else said that to me also. To duct tape it up and see if it would run correctly, to tempararily seal the crankcase, and if nothing was broken inside, to weld it up where it is!

 

[slag]

Re: Exhaust noise coming out from under cowl

I was being facetious. Something punched a hole in the case, probably a connecting rod, and it will happen again.

 

[nwcove]

Re: Exhaust noise coming out from under cowl

your power head is done! amazing that it still runs, but the loud exhaust noise is probably masking the rattle.....still cant believe that it still runs and can be used!!!!

 

[15hpevinrude]

Re: Exhaust noise coming out from under cowl (UPDATE)

Re: Exhaust noise coming out from under cowl (UPDATE)

So I decided I have to get going on figuring out what is going on with my motor. I did a compression test on the motor, and all 3 cyl. are between 135 and 140lbs. In the pics you can see both rod bolts are intact, the rod, rod cap, are all good. There is no noise when I turn the motor over by hand or doing the compression test. And this motor was still running when I shut it off last. There also is no indication of a problem by looking through the spark plug holes, pistons look good. Is it possible this could be a fluke. As I said in an earlier post, the rod cap runs extremely close to the crankcase, Is it possible maybe the crank deflected just enough to kiss the case, and there is nothing wrong with it?



View attachment 120405View attachment 120406View attachment 120407View attachment 120408View attachment 120409

 

[WernerF]

Re: Exhaust noise coming out from under cowl (UPDATE)

Re: Exhaust noise coming out from under cowl (UPDATE)

If the rod cap is running that close to the crankcase, will a broken reed valve inbetween be able to shoot a hole like this?

 

[boobie]

Re: Exhaust noise coming out from under cowl (UPDATE)

Re: Exhaust noise coming out from under cowl (UPDATE)

Could have also been the lower part of a piston broke off.