Well, I hope you do get lucky and don’t have to attack the grommets…Didn’t mean to jump the gun, guess I have seen too many of these. I remember the first one I discovered back in 1981. Just want to make sure I understand your post…The engine didn’t pump well before you replaced the water pump, correct? Any possibility that the water tube is misaligned and not going into the impeller housing grommet correctly? Perhaps someone bent up the water tube on a previous attempt. Perhaps the intake screen is plugged up with debris from your test tank. This engine “looks” fairly clean, has it been used in salt water? The gear housing castings are very thin under the forward part of the SS impeller plate, and erode badly….This might be causing the pump to suck air instead of water…Don’t get this confused with the other scalloped cut out under the impeller housing that is supposed to be there…
You can be fooled by using compressed air to blow through the water tube…The compressed air usually has enough pressure to “open up” the grommet allowing air through it, whereas the water pump doesn’t develop that much water pressure….Keep in mind that this 15hp probably uses the two water tube set up I mentioned in my earlier post, so if the outlet grommet was collapsed, you would still feel air coming out the telltale hose blowing through the intake water tube.
Again, I want to be wrong, so feel free to ask plenty of questions and provide any more info that might help us help you…I surely don’t want you to pull the thing apart needlessly….The grommet job isn’t too bad on fresh water engines, but salty ones usually require the torch…Sometimes trying to pry that powerhead off the exhaust housing can be a challenge also, be careful not to break the motor pan with pry bars.
There is a way to install the new grommets “improperly” that will avoid this issue in the future, hopefully we won’t get that far and it will pump fine with the new thermostat….Don
