bypass passage blown gaskets '85 150 GT with pics

[jriegle04]

J150STLCOH 1985 150 GT Johnson
It all started with sluggish acceleration then progressed to little to no performance above idle. I smelled more gas than I thought I should. I removed the cover and found gas/oil mix running down the crankcase. It wasn't obvious where it was coming from. I looked over all fuel lines and checked OMS for leaks and found nothing. Then I noticed a bubble from the bypass passage cover on cylinders 4 and 6 both on port side. 6 is the cylinder the OMS gets its pulse from. I ordered new gaskets yesterday and they will be here Thursday, I had never heard of this happening before. Does anyone have any insight as to why this would happen.

 

[jriegle04]

Re: bypass passage blown gaskets '85 150 GT pics added

Re: bypass passage blown gaskets '85 150 GT pics added

I seem to have some groves on the number 2 piston. It is the top piston in the middle picture and the next to last picture also. The cylinder walls look good though. The other 2 pistons on the port side both look very good as do the cylinder walls. Does anyone have any thoughts regarding the grooves on the piston from cylinder 2.

 

[jriegle04]

Re: bypass passage blown gaskets '85 150 GT pics added

Re: bypass passage blown gaskets '85 150 GT pics added

bump

 

[emdsapmgr]

Re: bypass passage blown gaskets '85 150 GT with pics

It's not normal to see this many grooves on a piston. To get this way, the piston is scuffing against the side of the cast iron cylinder liner. Perhaps insufficient lubrication on that cylinder. Could be running lean-from the leaking side covers. If fuel is leaking out, then air is probably leaking in-creating a lean condition. New gaskets and some sealer will cure that. Could also be a carb problem. Just in case, I'd pull the carb apart that feeds that cylinder and check the side of the carb that feeds #2. Pull the jets and look for any debris in them, esp the high speed jet. Debris could also cause a lean condition. Does not appear that you have any carbon around the rings, which can also lead to excess heat and scuffing. When you get it back together, you'll want to verify your compression readings on all 6 cylinders, noting how #2 compares to the rest.

 

[jriegle04]

Re: bypass passage blown gaskets '85 150 GT with pics

what kind of sealer. high temp atv silicone? or just some blue atv.

 

[emdsapmgr]

Re: bypass passage blown gaskets '85 150 GT with pics

OMC gasket sealing compound 508235, about $7-similar to a Permatex sealer.

 

[jriegle04]

Re: bypass passage blown gaskets '85 150 GT with pics

i just rebuilt the carbs on that cylinder. it wasn't getting any fuel flow previous to that thanks to previous owner not winterizing. the rubber tip of that needle had pushed its way out and the clogged the seat. After rebuild the carbs are now allowing fuel. That is when I noticed the leak on those bypass gaskets.

 

[nymack66]

Re: bypass passage blown gaskets '85 150 GT with pics

Do compression test and note in a log book you will have a bench mark for later on, That much scuffing on a piston is not a good thing you will see at lease a 7-8 lbs less on this one.