Stops pumping water when in gear

"7.5 Honda mid 80's Motor

"7.5 Honda mid 80's Motor stopped pumping water, checked the impellor found it damaged so I changed it. Motor worked for one or two sails then stopped again (motor is on a sail boat so it is not used very much) found some rubber from the first impeller in and around the thermostat. Worked again for a couple trips. This time I found that the impellor housing had over heat and spun loose and that I was given the wrong size impeller so I changed the impellor gaining as well as the housing. This time when I run the motor I noticed that it pumps water great when in neutral but as soon a I put it in gear it the water flow reduce to nothing by putting it back into neutral or increasing the throttle water flow returns. (Might have been like this before but had not noticed) On the suggest of another I changed the thermostat but this did not fix the problem. All ports appear clear when blowing through them. When the pump is working its water stream is thicker then it was before all this started and better then identical motors at our yacht club. Any Ideas? Is there a bi-pass and does anyone know the flow path for it?"

"It sounds more like you have

"It sounds more like you have some "crud" or bit's of impeller still haunting your system. I would suspect as the volume of water increases with the higher rpms, it's causing it to block your water tube, water channel etc.

I would drop the lower end again and try running some air through the system from the top end down to see if you can blow it out...."

"Thank You Graham for your com

"Thank You Graham for your comments, the system has been blown through a few times now. I did find the problem. When I changed the pump housing I did not take the ring seal ,located between the water pump housing and the water tube going up to the engine, off the old housing to put on the new one. Once I did the pump worked great, good as new. With the lower presure cause by placing the engine in gear, the water was able fall back down the tube and out the unsealed area until I increased the throttle."

Honda dude will know
i say u

Honda dude will know
i say u have a clogged water passageway somewhere

"I have a mid 80's 7.5 wit

"I have a mid 80's 7.5 with an interesting problem. The cooling indicator stream stops at mid rpm, but works at very low rpm in gear and at full throttle. Out of gear at idle (faster than in gear) the stream pretty much stops and at fast idle it stops. I've replaced the impeller, which had all it's pieces. Pulled the thermostat, cleaned the plates and scrubbed all the head openings good. Compressed air zips through easily, as does hose spray in the pee hole and in both of the other openings where the cooling hose attaches. Not sure if it is related, but when it stops, it puffs a little steamy air. Also, at low RPM in gear I can get the stream to stop by plugging the two tiny exhaust holes in the case...and it immediately returns when I open them up. The motor starts on one pull and otherwise has good power. I know steam is bad, so I'm determined to figure this out, but I'm stumped this time. Maybe the impeller housing? I also thought maybe the head gasket, but it runs so well...could it be?

-john"

"ok, I've looked some more

"ok, I've looked some more at this and there is definitely a very strong stream so long as the exhaust does not make it down to the bottom of the leg. I suspect a leak around the impeller plate. When I looked in this area under the plate (which was very dirty prior to the impeller change) I'n noticing what looks like a hole (vent type like many of the others on this engine) right under the plate by the shifter shaft. This does not make sense to me, as the rest of the area is sealed pretty good by the plate and a gasket. http://www.tqci.net/~jkriz/pump%20plate.jpg" I don't want to close it up if that is not the issue. pump plate

"Thanks to everyone that helpe

"Thanks to everyone that helped with this one. I'm now very good at taking this little motor apart. The problem turned out to be exhaust gas leaking into the impeller housing from two places. One was the little plastic bridge with two bolts that guides water from the intake to the impeller housing..this had a crack (chip missing) on the underside that was not easy to see and provided a path between the intake water and main leg cavity (which fills with exhaust completely before exiting the bottom of the leg). The other was a PITA! Under the metal impeller plate on the side against the shift linkage, there was corrosion that has gone through and bridged the leg housing to the impeller intake.....JB weld fixed that one. Some ebay parts, gasket material, a pair of scissors, and a tube of Hi-Tack later I can report that the water that comes out of the telltale is strong at all throttle positions and I can't make it stop even when plugging the exhaust idle holes at idle. It is also the temperature of the water at throttle and idle!"