83 Johnson 90 Maybe too cool

[Riverrat8428]

Replaced a complete water pump assembly on my cross flow. The new pump from OMC appeared somewhat differant than the old pump. I also replaced the thermostats and the check valves and springs. I took the motor on a fishing trip and it really pumped well maybe too well. I trolled a lot and the mid section of the lower unit where the two square hole are had lots of water coming out and got really black. I have since changed the thermostates again and the check valves and it seem about the same. I have a infa red temperature tool and this morning at the dock while idling in neutral I saw the temperatures on the top of the block just before the head to be about 98 degrees and the cylinder head to be about 114. Could the new pump be the problem may have more volume then the old style.. What should I do.

 

[ezeke]

Re: 83 Johnson 90 Maybe too cool

It is normal to have some exhaust through the exhaust relief ports. If the amount of exhaust is extreme, you may have dislocated the rubber seals on the inner exhaust housing, which frequently happens when servicing the gearcase. If you troll a lot, using a synthetic blend TC-W3 oil like XD-50 and a carbon treatment will help lower the plug fouling and carbon build-up. Champion QL77JC4 plugs are best for trolling in my experience.

The flow of water through the engine's cooling circuit is controlled by the thermostats on the way out of the engine and the rest of the flow is diverted, so the water pump is not the reason for the engine running cold if running cold is the problem.

My V4 crossflow engines did not run much above 110 when trolling, but would warm up a lot when running above 1,000 RPM.

 

[iwombat]

Re: 83 Johnson 90 Maybe too cool

What ezeke said.

The water pump pressurizes the cooling system. The t-stats regulate the water flow.

 

[aclmvh]

Re: 83 Johnson 90 Maybe too cool

Manual says the tstats should start opening at 125f and should be fully open (allowing full flow to the heads) by 144f. My digital thermometer shows my heads and block to be 138-144 at idle after warmup. I think your temp numbers are too low.