1990 90hp sticking rings?

[mignic]

Need some advice on Johnson 90 90. ser. R 08530852 Lower starboard cylinder only has 85 compression. The rest were 114-116. Did not do a decarb before we pulled the head last night. I wasn't aware it could help. There is some carbon in the ports in the cylinder but the walls look good to me but I am not very experienced with boat motors. What should I look for? I couldn't see any obvious leaks in the head gasket. What's my next step? Is there a way to pull the carbs n take off the rod bearing cap from the other side and pull that one piston? I was thinking of just puttin new rings on it. Any help appreciated. PS I did compression with good batt, throttle open, and all plugs out.

 

[wilde1j]

Re: 1990 90hp sticking rings?

You wouldn't be able to see carbon stuck rings by pulling the head off. Carbon, if there, packs the lands in the piston and causes the rings to get stuck. Install a new head gasket and get some SeaFoam and decarb. Hopefully one or two treatments might show improvement.

 

[tashasdaddy]

Re: 1990 90hp sticking rings?

Decarb, take a can of seafoam put 3/4 of it in the gas tank, with only 1 gallon of premixed gas. put the rest in a spray bottle. start the engine, and let it come up to temperature. then remove plugs, and them some real good shot of seafoam into the cylinders, replace plugs, let sit 15 minutes. restart, and spray the rest of the seafoam into the carbs, so the the motor almost stalls, wait and repeat until the seafoam is gone.then take for a wide open spin. then put in new plugs, ad premixed gas to the tank, and take it for a wide open throttle spin. it is going to smoke like a house on fire, during this process.

afterwards compression.recheck

 

[mignic]

Re: 1990 90hp sticking rings?

Ok thanks I have one more question. Lakes are far and few between in west texas, can I do this with water hose muffs? And about how long to run it?

 

[tashasdaddy]

Re: 1990 90hp sticking rings?

run it until the motor gets to operating temperture, then put in cylinders, and let sit. do not rev the motor over 1500 rpms, as it could cause a runaway, which cannot be shut down, other than removing fuel source.

 

[emdsapmgr]

Re: 1990 90hp sticking rings?

Once you get the decarb done on the engine, check both heads for temperature when warmed up. If either of the two thermostats is stuck open, it will cause that side of the engine to run cool, promote poor combustion-and that will eventually cause carbon buildup around the rings. Both heads should run 143-155 when idling in the water. Check temps with a laser temp gun.