reduced exhaust water

[rsford]

Any ideas about cleaning out the Yanmar diesel heat exchanger on a PSC 37? When the engine is running, seawater still come out the exhust, but it's a lot smaller volume than formerly. I've cleaned out the thru-hull for the seawater intake as well as the seawater strainer. With the seawater pump cover off and the intake line open, seawater flows out freely at the open pump. I've also replaced the seawater pump impeller even though the old one looked fine.

I'm concerned that, despite the above actions, the volume of exhaust water remains diminished, even though the engine has not yet over- heated. In case marine growth built up during a period of disuse, I've wondered about pumping Liquid Plummer into the seawater inlet of the exhanger for a little while and then flushing it out. Removing the heat exhanger looks like rather serious engine work to me, so I was hoping for a simpler fix. Thanks.

Bob Ford
s/v Talos IV, 1995 PSC 37 #306

[camaraderie]

First step is making sure you have full flow of water between the through hull and the perko filter. Often barnacles, kelp, plastic can restrict water flow. Liquid plumber won't help...but often a dive overboard with a long screwdriver and/or coathanger can dislodge whatever is restricting the flow.
If that is not the problem...and you think the impeller is good...check the flow by removing the connecting hose for a few seconds with the engine running. If that check out...it is on to the heat exchanger I'm afraid but it is NOT that difficult a job. Alternatively to removing the exchanger if you are pretty sure the blockage is NOT a piece of impeller...is to use muriatic acid solution at the engine intake and let it run through until you see it coming out the exhaust...let it sit for a few minutes and then flush it thorugh by running the engine normally. That will often clear the pipes. Otherwise they need to be reamed out physically.
Good luck.

[sailaway21]

Discharge of which upon the navigable waters of the US will earn you a $10,000 fine. But it will probably work.(g)

[SailorMitch]

There also could be a blockage in the exhaust elbow. Need to remove and clean that if you have no idea when it was last done. I'd check that before I'd check the heat exchanger.

[rsford]

Thanks for the suggestions.