Hi,
I own an N343 which is equipped with an VP MD17D
engine with VP fresh
water cooling system. I had exchange the fresh
water pump 3 years ago as the one before did leak.
Last
winter the
engine got fitted with a new (used but tested)
exhaust manifold. The engine did never make any problems, starts immediately, never had heat problems, smokes a little (grayish, definition no stream).
We put the
boat in the
water end of May and had to
motor from ship yard into the marina, which is in total 2.5 hours. For the first 2h10min everything was OK, temperature around 75-78C (at the thermostat housing). We motored at around 1800-1900
rpm. Then the temperature started slowly to increase. We still made it into the marina. When reducing
rpm in the marina the temperature started to increase towards the red an just touched the red when we finnished
docking.
What did we do since then:
- checked and changed impeller (the old one was not worn at all and just fitted during the
winter, ... anyway)
- flip the seawater
pump lid around as it was a bit worn
- checked the seawater intake
- dismounted the
heat exchanger and checked it for blockage (i was newly fitted last year)
- checked the piping of the fresh water side
- drained the
coolant to see whether the is any dirt, mud ... - comes out fine and clean
- checked the thermostat
What we can see is, that the freshwater pumps (I do at least a good amount of
coolant being pushed into the expansion tank). What I cannot judge is whether the
pump develops sufficient pressure to pumps a sufficient flow through the heat exchange and the cylinders.
We can run the engine without load in different rpm with no issues. As soon as we put load on it it starts to overheat. The temperature of the heads and the cylinders is as well considerably higher then the temp at the thermostat housing (20 degrees more). The
heat exchanger gets warm, but I somehow feel that it used to be hotter in the past (but have no data to prove).
Anyone any idea what else to do/check?
Thanks for any idea.
Frank