Renault inbrd overheating...descaling? waterlock?

[txmilke]

Somebody on another post mentioned "descaling" an engine in the hopes of solving an overheating problem. What is this? Is there some chemical that you can run thru it to clean it out?I have a 1980 H27 with Renault RC8D inboard. I can run the engine in the slip at half throttle for a half hour with plenty of water flow and it's totally cool. However, when I head out it overheats in a remarkably short time and water flow stops. I can backflush the engine with a pressure water nozzle and resume water flow, but the same thing repeats...I've removed and cleaned everything I can access. What's next? My local diesel mechanic won't look at it until I tell him I'm ready to repower. I'm not.ALso, this boat has a W.H. den Ouden waterlock (model 50LP?)installed, apparently around 1991. Does anyone know if this boat originally came from Hunter with anything besides hose installed between the exhaust and the transom?I'm starting to get a bit distraught....Zut Alors!!!Tom Milke

 

[Fred Ficarra]

Tom

I have no idea what your setup looks like. But the failure is 'dynamic'. When the boat moves, water doesn't. Do you have a scupper partially blocked? Is this a new problem? What changes were made prior to the condition manifesting its' self? Doesn't sound serious. Plenty of static water flow is a good sign.

 

[txmilke]

dynamic and then again, not...

Hi Fred,Thanks for your comment. The dynamic characterization is true, in that the problem doesn't occur until the boat starts underway. HOWEVER, once the waterflow stops, it stays stopped until I backflush it and start over. Hmmm...I'm attaching a schematic of the flow.Tom

 

[txmilke]

dynamic and then again, not...

Hi Fred,Thanks for your comment. The "dynamic" characterization is true, in that the problem doesn't occur until the boat starts underway. HOWEVER, once the waterflow stops, it stays stopped until I backflush it and start over. I can move large volumes of water OUT thru the strainer, so I'm assuming that it's not blocked (although I haven't gone diving yet).Hmmm...I'm attaching a link to the schematic of the flow.Tom