Johnson 15hp 4 stroke water telltale intermittent...

[bolkow]

Good Afternoon.

Johnson
J15R4SR
S23031630
04/2004
Freshwater only

Original problem: no water flow at telltale (pilot water hole).

Verified no blockages in all passage ways and hoses. Back flushed with water no discrepancies noted.

Removed lower unit and water pump housing. Found grommets flexible with top grommet tight on shaft, old impellor pre-set and worn, and interior housing/bottom plate shiny with no grooves. Elected to replace impellor with kit P/N 5033106 (impellor, bottom plate, gasket).

On test run at idle, with motor submerged in barrel, noted steady stream at telltale but at a lower pressure than normal. Increased throttle and stream increased in pressure but then started to pulsate at a constant rate regardless of throttle movement. When returned to idle, water stream returned to low pressure, steady stream.

Rechecked for blockage: none. Pulled thermostat found a bit dirty but function checked good in pan of hot water.

Before disassemble again, are there any other things to check?

I’m leaning to the housing is worn or a grommet is leaking. If nothing else appears faulty, will purchase water pump kit and replace everything.

Can anyone verify that water kit P/N 0394711 is correct for this motor? My parts book only shows individual part numbers and does not show this kit number.

Thanks.

 

[racerone]

Perhaps not enuff water in your test set-up.----Launch the boat and see how tell tale behaves.

 

[bolkow]

Perhaps not enuff water in your test set-up.----Launch the boat and see how tell tale behaves.

Test set up is a 300 gallon stock tank which has worked for a number of motors over the years. But I did take it to the landing and checked. Same symptoms. Anything else? Thanks.

 

[Bosunsmate]

Id remove the LU and attach a hose and run it on that.
That way you may isolate it to the LU or a problem in the head such as compression gases somewhere entering the water jacket.

 

[bolkow]

Id remove the LU and attach a hose and run it on that.
That way you may isolate it to the LU or a problem in the head such as compression gases somewhere entering the water jacket.

Removed lower unit and ran with hose. Telltale stream steady throughout run.

Pulled pump housing and noted water between housing/new lower plate. Installed old lower plate with housing and ran in stock tank. Idle telltale steady but still have pulsing stream at higher RPMs. However, top end stream pressure is much higher now.

I plan to replace the housing rubber grommets and permatex the housing/plate/gasket and see what I get. I rather not use sealant at the housing, but there's no pump kit for a 2004 and I don't see any reason to change the housing at the moment.

Any other possible thoughts? Thanks.

 

[Bosunsmate]

Just check all exhaust outlets in the leg etc are unblocked. Good luck