1986 Johnson 150 Running Hotter with Higher Water Pressure

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Author Topic:   1986 Johnson 150 Running Hotter with Higher Water Pressure

vkr posted 07-24-2011 01:00 PM ET (US)
My engine temperature has historically run with the needle in the 2:30 (hour hand) position on the standard OMC green & red temperature gauge. The water pressure historically ran at approximately 5 psi at idle and 18 psi at full throttle.

Unfortunately, given a crazy schedule, I just burned off the winter fogging oil yesterday. The engine temperature is running warmer in approximately the 2:00 o'clock position (this is at the 75% point in the green zone) and the water pressure gauge is running at 15 psi at idle and 28 psi at wide open throttle. It is important to note that I am not overheating in the red zone of the temperature gauge and I am not getting any overheat alarms.

I would have thought I would see a lower water pressure with the higher engine temperature if in fact the impeller, being in it's third year, has relaxed and is not pumping efficiently.
Does anyone have any thoughts as to what may be causing the higher water pressure and higher engine temperature? Thanks!
Tom W Clark posted 07-24-2011 01:31 PM ET (US)
I suspect you have an internal restriction in your cooling system and this restriction is causing higher water pressure at the point where the water pressure TEE is inserted.
The restriction could be anything from Mud Wasps to corrosion.
It is important to figure this out as I believe the temperature gauge is only measuring head temperature on one head. If the water restriction is on the other head, it could be getting quite hot.
You might want to try using an infrared thermometer on your motor while its's running, to locate any hot spots.
vkr posted 07-25-2011 08:56 PM ET (US)
Tom, Thanks for the reply. Given I have only one temperature gauge, you bring up a good point. I'll see if I can obtain an infrared thermometer and take some readings off both heads. I'm hoping my other head is not hotter than the head with the temperature gauge sensor. As I mentioned, I did not receive any high temperature warning horns. I believe the warning system has a temperature switch in each head and they are wired in parallel. If one closes the horn sounds. It is my understanding that the warning horn should sound at or around 211 degree F. In addition, the cooling system should be keeping the temperature below 155 degree F.
I know this is a long shot, but let me know if there are any tricks to flushing/opening the system or relieving any cooling system fouling without pulling things apart too far.

whaler1234 posted 07-25-2011 11:52 PM ET (US)
You could try this:
http://www.saltawayproducts.com/SaltBuildRemoval.htm
I'm doing the same and am noticing the salt is breaking down considerably behind the thermostat.
vkr posted 08-03-2011 01:24 PM ET (US)
With the engine running, I used an infrared thermometer to take temperature readings around the cylinder heads and the thrmostat covers. The temperatiures ranged from 130 to 148 degrees farenheit. I did not feel comfortable hanging over the transome to take temperatures with the engine running at 5000 rpm's as the service manual suggested (temps should be below 120 degree F at 5000 rpm). However, I did take measurements quickly after running at high speeds, and they seemed to return to the 130 to 148 degree F range.
I did notice that my water pressure gauge now is zeroing out at 15 psi when the engine is off. I didn't notice this until today. I'm thinking the gauge is shot and it may just be giving measurements from a "new zero point". Given the acceptable temps, does this seem like a reasonable explanation?
Can someone suggest an available replacement water gauge given the old/1986 OMC gauge design is no longer available? Possibly I should also replace the water temperature gauge. Any thoughts? Thanks

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Author	Topic: 1986 Johnson 150 Running Hotter with Higher Water Pressure
vkr	posted 07-24-2011 01:00 PM ET (US) My engine temperature has historically run with the needle in the 2:30 (hour hand) position on the standard OMC green & red temperature gauge. The water pressure historically ran at approximately 5 psi at idle and 18 psi at full throttle. Unfortunately, given a crazy schedule, I just burned off the winter fogging oil yesterday. The engine temperature is running warmer in approximately the 2:00 o'clock position (this is at the 75% point in the green zone) and the water pressure gauge is running at 15 psi at idle and 28 psi at wide open throttle. It is important to note that I am not overheating in the red zone of the temperature gauge and I am not getting any overheat alarms. I would have thought I would see a lower water pressure with the higher engine temperature if in fact the impeller, being in it's third year, has relaxed and is not pumping efficiently. Does anyone have any thoughts as to what may be causing the higher water pressure and higher engine temperature? Thanks!
Tom W Clark	posted 07-24-2011 01:31 PM ET (US) I suspect you have an internal restriction in your cooling system and this restriction is causing higher water pressure at the point where the water pressure TEE is inserted. The restriction could be anything from Mud Wasps to corrosion. It is important to figure this out as I believe the temperature gauge is only measuring head temperature on one head. If the water restriction is on the other head, it could be getting quite hot. You might want to try using an infrared thermometer on your motor while its's running, to locate any hot spots.
vkr	posted 07-25-2011 08:56 PM ET (US) Tom, Thanks for the reply. Given I have only one temperature gauge, you bring up a good point. I'll see if I can obtain an infrared thermometer and take some readings off both heads. I'm hoping my other head is not hotter than the head with the temperature gauge sensor. As I mentioned, I did not receive any high temperature warning horns. I believe the warning system has a temperature switch in each head and they are wired in parallel. If one closes the horn sounds. It is my understanding that the warning horn should sound at or around 211 degree F. In addition, the cooling system should be keeping the temperature below 155 degree F. I know this is a long shot, but let me know if there are any tricks to flushing/opening the system or relieving any cooling system fouling without pulling things apart too far.
whaler1234	posted 07-25-2011 11:52 PM ET (US) You could try this: http://www.saltawayproducts.com/SaltBuildRemoval.htm I'm doing the same and am noticing the salt is breaking down considerably behind the thermostat.
vkr	posted 08-03-2011 01:24 PM ET (US) With the engine running, I used an infrared thermometer to take temperature readings around the cylinder heads and the thrmostat covers. The temperatiures ranged from 130 to 148 degrees farenheit. I did not feel comfortable hanging over the transome to take temperatures with the engine running at 5000 rpm's as the service manual suggested (temps should be below 120 degree F at 5000 rpm). However, I did take measurements quickly after running at high speeds, and they seemed to return to the 130 to 148 degree F range. I did notice that my water pressure gauge now is zeroing out at 15 psi when the engine is off. I didn't notice this until today. I'm thinking the gauge is shot and it may just be giving measurements from a "new zero point". Given the acceptable temps, does this seem like a reasonable explanation? Can someone suggest an available replacement water gauge given the old/1986 OMC gauge design is no longer available? Possibly I should also replace the water temperature gauge. Any thoughts? Thanks