'85 25 johnson, serious water circ. issues update: WOOHOO

[RWKellenberger]

Hello, new here. I have an 85 25 horse Johnson and I have serious issues with water circulation. Water will come out of the pee-hole at idle in the water, and when I put it in gear to get underway if I go faster than idle speed, it stops. But I can put it in gear up against a piling at full throttle and it will pump just fine. I have replaced the water pump, water jacket gasket, head gasket, intake grate, thermostat, cleaned everything out and a new gasket around the copper pipe at the powerhead. The motor is on a flat bottom john boat. A mechanic told me its cavitating somehow. any thoughts? EDIT: Cylinders also have 100 psi compresion each, thought head might be warped enough to let exhaust pressure into chamber between piston sleeves and block preventing water circulation, is that possible? seems unlikely since it pumps at WOT against piling. also could pump cavitate because I took off the hydrofoil? never ran w/o it until today.

 

[Cofe]

Re: '85 25 johnson, serious water circ. issues

Re: '85 25 johnson, serious water circ. issues

May have sheared the plastic impeller key. Sometimes it grabs....other times it don't. Were your water tube grommets ok?

Could be cavitation. For optimum performance the plate above the propeller is at water surface level at WOT.

 

[RWKellenberger]

Re: '85 25 johnson, serious water circ. issues

Re: '85 25 johnson, serious water circ. issues

Cofe: I don't think it's the impeller key, when I took the pump out to check it and replace the gaskets, the impeller was siezed onto the driveshaft, it was also on there straight. Although the pump housing seemed to be melted a little bit but the metal dish was still in the right position. The motor has worked fine before, just tried again with hydrofoil on and no luck. Might go for water pump #3 just for piece of mind. impeller might have gotten hot and fins arent stiff enough to give sufficient pressure/suction while water moving over lower unit?

 

[ezeke]

Re: '85 25 johnson, serious water circ. issues

Re: '85 25 johnson, serious water circ. issues

Thermostat OK? if so, you might want to check the three water passage deflectors in the cylinder cooling passages. They are about due if they are originals.

 

[RWKellenberger]

Re: '85 25 johnson, serious water circ. issues

Re: '85 25 johnson, serious water circ. issues

Where are the deflectors located? are those the rubber pieces between the piston sleeves and the block? how do you replace them?

 

[ezeke]

Re: '85 25 johnson, serious water circ. issues

Re: '85 25 johnson, serious water circ. issues

You can usually remove them with needle nosed pliers and just push the new ones in. Trim flush to the flange with a razor blade.

 

[Cofe]

Re: '85 25 johnson, serious water circ. issues

Re: '85 25 johnson, serious water circ. issues

Did the wear plate under the impeller look ok? They must be real Smooth.

 

[RWKellenberger]

Re: '85 25 johnson, serious water circ. issues

Re: '85 25 johnson, serious water circ. issues

so the water intake grate....either wrong model or poorly made. it had extra plastic from where it was molded that was preventing water from pushing up into the pump. this is my third intake grate i have put on here, and they were all different designs. well anyway, problem solved. thanks for all your help.