75 Johnson 50 hp...no compression bottom piston.....help???

[barrieboi]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

Yes cylinder walls look mint....top cylinder even look like it was done recently...do i need to replace it? I am wondering if my waterpump isnt working and thats what happened cause I had this boat out a few weeks ago and it ran fine. How would i check that? I have water coming out the top little spout and the top side spouts so i think its workin finre but like I said I am no expert and have to do most work myself....I could just happen cause of age or you think something causeed it....it was pretty chewed?My neighbour has an old motor he said I can take apart and see if the cylinder fits?

 

[barrieboi]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

Thermostat was full of ****....Pine needles and everything.....what do i look for to figure out what happened?<br />It was all chipped on the end?

 

[barrieboi]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

Well anyone have an old broken down 50hp Johnson....or anything similar? Or know where I can get one in Ontario?Canada?

 

[papasage]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

i have some parts for a 74 dont know if they will fit a 75 . i know 72 to 74 is the same. e mail me at papasage10@yahoo.com. i am not in the outbord buisness .i have a couple of 50 that i use and got some extra parts.

 

[sparkroost]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

cylinder wall was mint? What did the piston look like? did the head gasket fail?

 

[barrieboi]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

Im notsure the piston looked like a little piece of metal was stuck inside the motor the top of the piston had a whack of little nicks in itbut the walls were fine?????? I have no idea.....If anyone in Ontario has a piston for this they want to sell cheap get in touch with me @ cchambers6159@hotmail.com...Id appreciate it.

 

[Hooty]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

Could you possible post a foto of the piston top?<br /><br />c/6<br /><br />Hooty

 

[barrieboi]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

I have no way of posting a photo but picture someone with a really sharp screwdriver stabbing the top of the piston a thousand times or more.......lots of little dents.......I want to know what caused it befor ei fix it...

 

[sparkroost]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

was the piston top clean or black? You could have had carbon buildup and snapped a ring. The dents are from the ring getting smashed on top of the piston. If the piston is clean you got water in the cylinder. What I don't understand is why you have no compression. Even with no ring you should get some air. Have you rotated the flywheel so that the dented piston reaches the top, then rotate left and right to see if the piston stops moving with slight left to right movment of the flywheel(it will stop moving for about 1 deg, and that should be it)?<br /><br />Was the plug gap closed after removal?

 

[Hooty]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

Might have swallowed a read or a screw or a nut or a ring.<br /><br />c/6<br /><br />Hooty

 

[barrieboi]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

nope the plug gap wasnt closed...i know what u mean...but its clean and i know it must be somethin got in there......metal...i think may be it was just time....

 

[barrieboi]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

Hey all I just finished my motor put new piston in...but before i try it I wanna know what would blow a hole in the piston....side? Plus the thermostat thing was all jammed? Loss of cooling?

 

[barrieboi]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

Also what about the high speed jet on the carbs? The usual one and a half turns?????

 

[sparkroost]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

Did you remove all the carbon? Also.. did you check your reeds to see if they are all there? Were the shavings all aluminum? Hate to see ya blow her up first time out.

 

[jim dozier]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

The low speed (idle) jet would be about 1 1/2 turns out from stopped. The high speed jet would be fixed. Rebuild the carbs while you have it out with particular attention to the fixed high speed jets. You don't want to run this sucker leaned out and fry the new piston.

 

[barrieboi]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

hey im back everyone well the boat runs well......if I wanna keep squeezing the ball to keep the gas flowing....it idles and everything great but as soon as im in gear and try to go fast it bogs out but if i keep squeezing the ball on the hose it just kicks right in and fly's.....any suggestions?

 

[jburch]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

Your story sounds familiar, I have the same problem. My problem leads to the vacuum line from the crankcase that provides the vacuum pulses which actuate the fuel pump. I don't have any vacuum at this port, but perhaps the hose on your engine is bad or leaking or pinches off if its not a vacuum rated hose. I'm considering an electric fuel pump. Hope you find the problem, it'll probably solve mine as well! Good Luck!

 

[JerseyJim]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

its possible that your fuel pump went south and leaned the motor out - and that cylinder just went first... <br /><br />If you are squeezing the bulb to keep pressure in the engine, 9/10 its a fuel pump.

 

[jburch]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

Your problem was mine.... recently rebuilt engine, runs okay, but have to keep squeezing the primer bulb. Take the vacuum line off the carburetor while the engine is running and see if you have any vacuum pulses. If so, then possibly a fuel pump, etc. But if not......<br />My engine didn't have any vacuum at the fuel pump, so it won't pump. I took the carb's off and the plate that the vacuum port is mounted to, the gasket didn't have a hole at the vacuum port location, so it was blinded. I opened up the hole and reinstalled, it runs okay now... at least in the barrel, it doesn't run out of fuel anyway. If all else fails, check the gasket behind the vacuum port on the block.<br />Good Luck!

 

[barrieboi]

Re: 75 Johnson 50 hp...no compression bottom piston.....help???

k...I think it could be a fuel pump cause right now im using a skidoo fuel pump until i get a new one from an old Johnson....think thats the problem though?