GNJ

I'm leaning towards the pump acting up but I would like to see if any one else agrees.

The water pressure guage on 1 motor is acting up. The other motor is fine. At idle, it oscillates from 5psi to 0psi about every 30 seconds and stays at 0 psi for about 5 - 10 seconds then returns to normal. At 3000 rpm I have 22psi and then in about 30 seconds it drops to about 4 - 5 psi for about 5 - 10 seconds. This worries me. The left side riser gets too hot to touch when the water pressure gauge drops, but the right side says cool. The other engine's 2 risers stay cool to the touch. The oil temp on the problem motor is about 20* higher than the other. They are rebuilt motors with about 6 hours. I tried swaping the mercrusier stat housing from one motor to the other thinking the thermostat or something in the housing was acting up but the problem did not follow to the next motor.

The raw water pump is about 2 years old but not a whole lot of time on it maybe 20 - 30 hours?
Could the pump be worn and cavitating causing a kind of cycling effect? Any one experience this before? I've checked up stream and down stream and water seems to be flowing through coolers and the exhaust risers. So I'm stumped....
Can anyone help?
Thanks,
Gary

32' Fountain:
Roller 502's
ZZ502 cam's
Merlin Single Plane intakes
850 DP Holleys
Revolution Marine Exhaust

lowfunds

i am guessing you are using bravo drives. if so if you are running in saltwater sometimes the water hose in the transom assembly is the problem. if your x-dimension is high what happens is the water neck entering the boat is above the water line and see's the air and corrodes around the hose causing it to collapse the hose which will restrict water flow. in order to check this problem you need to remove the plastic neck in which the 1 1/4" hose is connected. after removing the nech look at the hole coming into the boat on the transom assembly it is probably full of white salt build up and collapsing the hose. if all is good there i would more then likely replace the raw water pump as a assembly meaning impeller ,wear plate and pump housing. oh don't remove that neck unless your boat is out of the water. i just did a fromula the other day with this problem. it is very common in saltwater applications.

zt260

It's doesn't sound like the pump. Switch the pumps and try again. A restriction sounds more likely.

GNJ

Thanks Lowfunds and ZT260 - Yes bravo drives with high X dimension and salt water application. Now that you mentioned the transom assembly, it makes sense. Did yours make the H20 gauge act up as well?

mats

Sounds like a restriction. Considering the psi variations, I would guess the suction side as have been suggested.

cig1988

I would with the easy process of elimination. Unhook your psi line and run a wire thru both the line and fitting. Unhook from the guages and blow with compressed air. Make sure the hoses are somewhat secured in the bildge to avoid the garden hose snake effect. Switch the hoses that connect to the gauges but remember port/starboard will be reversed. If it still reads low switch the hoses back where they belong.

Lowfunds hit a nail on the head with the restriction problem in the gimbal housing. Had that problem myself years ago. If everything else checks fine your sea water pumps are the problem. Sort of a PIA to switch them from side to side but may be worth doing it as a process of elimination.
Let us know how you make out. Hope this helps.

jdub

iTrader: (1)

mechanical or electric sender?

GNJ

The H2O gauge is mechanical. When the motors were out both lines from the engine block to the water pressure gauge were cleaned out since I had found them plugged up with sand. I am gonna try getting to the gimble housing tomorrow and will post results once I find the issue.Not gonna be easy, sSince these motors are in a 32' fountain and there isn't much room to work on it. You have to be a contorsion artist to reach many things. URRUGH!

blownincome

I would back flush the coolers to make sure there is no debris(sea weed/impeller parts stuck in line)up stream from the raw water pump.

lowfunds

welcome to my world. i got a lot of cuts,brusies and a bad back from being a marine mechanic for 20+ years. trust me i am burning out of this business and i am not even 40 yet.