88 SPL Johnson Ignition/Overheating/Carbon Issue?

[runninfarmer]

I've posted on here a couple times about my 1987 88 SPL Johnson model J88MSLCUS. I've replaced the water pump, new exhaust cover gaskets, new t-stats and replaced the rectifier and starboard powerpack. When idling the starboard head is much cooler than the port side. At higher rpms in neutral though the port side head cools down. Is there something wrong with the t-stats I put in or is it ignition related? The plugs are pretty carbed up. I put mystery oil in the premix, maybe there's some decarbing going on? The motor hadn't ran for 8 years or so. I've got the rebuild kits for the carbs, just been waiting on doing them. I've seen a few similar threads on this. Are the starboard cylinders supposed to run cooler? Here's a couple pics:


Thanks for the help!

 

[fireman57]

Re: 88 SPL Johnson Ignition/Overheating/Carbon Issue?

Sounds like you have a blockage on the one side. You need to pull the head, easy job, and run a stiff wire through the water jackets and then find a nozzle that will fit your hose and the inside of the jackets and flush whatever crud that is in there out. Make sure you use a new head gasket and torque it to specs. Run it a few hours and then retorque. Sounds harder than it really is.

 

[emdsapmgr]

Re: 88 SPL Johnson Ignition/Overheating/Carbon Issue?

Once the boat planes out the pressure relief valves in the thermostat housing open up. When this happens, the powerhead is flooded with extra cooling water and the powerhead temps will go down maybe 20 degrees. (this might happen on the trailer if you rev the engine. Probably why the port head cools down at higher rpm's. At idle, the heads should be 143-150 (maybe 155 in a warm lake in the summer.) If you have new stats, new impeller and still have cooling temp issues-you might want to pull the heads. Check the placement of the rubber water deflectors by each cylinder. Sometimes debris will block/disrupt the water flow inside the block and that can cause uneven cooling. You might consider removing the cyl head covers to visually check the cooling passages in the heads.

 

[Bob_VT]

Re: 88 SPL Johnson Ignition/Overheating/Carbon Issue?

Being the motor has not run in 8 years....... my bets are on the T-stats AND water deflectors in the heads.