Pressure Relief Valve ?- '98 Johnson 70

[goldenmonkeyboy]

I have noticed when I go full throttle high revs the water stops coming out of the water pump telltale. Its a Johnson 1998 70hp and the manual says the water circulation in the cooling system is controled at low revs by the thermostat when the engine goes to high revs the water is controlled by the pressure relief valve. Is my valve faulty or is it common for the water telltale to switch off at times

 

[sharkcat]

Re: Pressure Relief Valve ?- '98 Johnson 70

I dont have alot of experience with johnson engines but I think if there is no water from the tell tale there is not a lot of water going thru the engine.I would check the poppet valve & the water pump as you could do alot of damage if you overheat it!!

 

[Joe Reeves]

Re: Pressure Relief Valve ?- '98 Johnson 70

Golden..... You are describing a failing water pump. There may be another explantion but the above is the most likely one.<br /><br />Drop the lower unit, dismantle the water pump and inspect it. In all probability, it will require replacing. It would be a good idea to replace the thermostat at the same time.<br /><br />To check the warning horn, have the key in the ON position, then ground out the heat sensor at the cylinder head (tan wire). If it sounds, fine. If it doesn't, find out why!

 

[goldenmonkeyboy]

Re: Pressure Relief Valve ?- '98 Johnson 70

Hi Joe<br /><br />Thanks for your help. But can I check with you before I dismantle it all. I do get a strong telltale jet when in low revs its only when I am planing at say 20-30 knots I notice no telltale water. I have a manual and have tried to do a temperature horn warning test but can not find the right wires!! I ran the engine this morning on some muffs and the water from the tell tael got quite hot after say 8mins tick over but then cooled - is this a good enough test that the thermostat OK - what about this pressure relief valve? Thanks

 

[goldenmonkeyboy]

Re: Pressure Relief Valve ?- '98 Johnson 70

The colour of a tan wire - is that like dark brown or light beige brown? I'm trying to fing this heat sensor to ground it for the horn test!!

 

[goldenmonkeyboy]

Re: Pressure Relief Valve ?- '98 Johnson 70

The colour of a tan wire - is that like dark brown or light beige brown? I'm trying to fing this heat sensor to ground it for the horn test!!