Operating Temp 90 HP 4cyl 1995

[Shadowjaguar1]

Quick question. Overheating problem. Cleaned out water ways behind the heads. They were pretty well clogged. Tell tale is showing good water flow. Temperatures using an IR show 130 -140 F when using rabbit ears and good hose pressure. When I lower water pressure to simulate still water one side goes to 170 F. Impeller and pump issues or (I hate to think it) internal power head clogs? Thanks.

 

[bob johnson]

Re: Operating Temp 90 HP 4cyl 1995

what model number??? I dont think 170 is such a big issue.

actually when its summer time and the water is 75 degrees that temperature at idle might be higher!!! your garden hose is probably suplyying pretty cold water..maybe 50-60 degrees!

can you moniter the temp drop telling you that the thermostats opened and see the temps they did so at??

just make sure the t stats open!! at 130 -140 they might not even open!!

recheck when lake water temps rise and make sure it doesnt go much over 180......you should be ok...cause when you throttle up, the temps will drop!!

bob

 

[Shadowjaguar1]

Re: Operating Temp 90 HP 4cyl 1995

J90TLEOR. I am always in warm water so I removed the thermostats. I am getting ready to drop it in the water (salt) and recheck the temps. What would cause it to overheat when throttling up. That is what happened the previous issue.

 

[bob johnson]

Re: Operating Temp 90 HP 4cyl 1995

that model is a cross flow I think. they have little fingers in the water passages that get clogged or out of place..that can block water flow.

a LEAN condition in one or more carbs could cause a hot running motor..

mechanical friction...galling on the cylinders can cause friction

you have to address one thing at a time...

most guys say not having a T stat is bad ......
a weak water pump..worn impeller could cause an overheating issue

do you have a water pressure guage??

have you ever had the heads off???

bob

 

[Shadowjaguar1]

Re: Operating Temp 90 HP 4cyl 1995

Just put it in the water. I kept it at low RPM's and the average temp was 135 around the block and heads. When I boosted the throttle a little I found 155 at one spot. Tomorrow I am replacing the water pump and impeller. I am praying for the best. Thanks again.

 

[boobie]

Re: Operating Temp 90 HP 4cyl 1995

Did you have the thermos in when you tested it? They should be there to keep the operating temps up at idle and to prevent condensation. The engineers put them in there for a reason. If you know your w/p and the thermos are good you have other probs. The only proper way to check the system out is in the water, not on muffs.

 

[James R]

Re: Operating Temp 90 HP 4cyl 1995

From what has been said you have no history on the water pump. Water pump impellers should be replaced routinely at least every two seasons. To risk blowing an expensive motor for something as cheap as an impeller defeats logic.

 

[Shadowjaguar1]

Re: Operating Temp 90 HP 4cyl 1995

Boobie, I did place it in the water. IR Thermometer was pointed at all points of the motor while running in the water.

James, I agree. I was very careful today when running the motor in the water. But when I noticed that the temp increased with the throttle increase the next logical step is the impeller.

 

[emdsapmgr]

Re: Operating Temp 90 HP 4cyl 1995

A crossflow for sure. Always good to replace an impeller. The stats in that engine should begin to open at 143 degrees. You will get an overheat warning at 212 degrees, and the engine hot horn will silence when the powerhead temp gets back down to 175. If you are getting temps around 170 degrees, during normal running, that's way too high, in my humble opinion-it's just below the overheat range. That engine should idle close to 145-150 normally, perhaps up to 155 when idling in gear in a warm lake in the summer. Normally, when the boat goes on plane, the pressure relief valves inside the thermostat housing will open and will flood the powerhead with extra cooling water. It's normal for the powerhead temps to go down below 143 when planing when those valves open. If the engine idles ok tempwise, but overheats the faster it goes, I'd look for some type of water flow restriction. Such as, salt inside the head covers or similar restriction inside the powerhead water passages. Make sure the 4 rubber water diverters are in their correct position next to the cylinders.