Overheating westerbeke

[jfhspike]

This isn't so much a question as an answer that I hope others might find helpful.

I've had a Westerbeke 4-107 and later a 4-108, and at various times have had to diagnose overheating problems on them. So what do you do when you know that the engine should be running at 180F, but the needle on the meter says 190F, or even 200F?

There are a ton of good answers here, and there's no great need to repeat them, although I'll make a particular pitch for checking where the output of the water pump">raw water pump enters the oil cooler, probably through a 45 degree elbow. That's a prime spot for a broken bit of impeller blade to fetch up, and an even MORE prime spot for scale to form. My engine started running hot when that elbow was so clogged that there was just a 1mm hole through the middle of the obstruction...until then, things seemed fine!

But before you do any of that, here's a tip I've never seen mentioned on this forum, and one that's been the answer for me twice:

check the ground wire on your temperature gauge!

If there's corrosion there, or a bad connection, then the ground-point of the gauge ends up raised a volt or two above true ground and this (for gauge-design reasons I don't entirely understand) causes the gauge to read high. On cars, this is seldom a problem, because "ground" is everywhere, and the case of the meter is grounded, etc. But on a boat, instruments may well be installed in fiberglass, and need a ground wire. In this diagram from Teleflex, you can see the ground wire ("G") gets attached at a post that also holds the bracket that holds the instrument in place (shown as a wide horizontal strip here):
https://imgur.com/4RnT4tZ

Typically you put the meter through a hole in some thin metal (or fiberglass) panel, put aluminum bracket in place over that post, put the ground-wire ring terminal on, then a lockwasher, then a nut. Tightening the nut presses the "feet" of the bracket against the panel, and then the crossbar of the bracket eventually presses against the instrument itself, the nut locks in place, and everyone's happy.

But if your panel is, say, 1/2"-thick cored fiberglass, then the legs will "bottom out" long before the crossbar gets anywhere near the meter, and the resistance to tightening the nut comes only from the bending of the crossbar. That works fine...until it doesn't.

One solution is to trim the legs to the exact length needed, which is a pain in the neck. Another is to do the following: spin an EXTRA nut well onto the post. Then install the bracket, and press everything into place, and then back off that extra nut until it's almost touching the back side of the bracket. Then put on the ground wire ring terminal, the lockwasher, and the normal nut, and snug it up. The bracket will bend a tiny bit, and then the extra nut will provide something for you to tighten the first nut against...

Here's a picture showing a typical installation:
https://imgur.com/7UOmKBl

You can see the aluminum bracket running left-to-right, and the post with a wire, lockwasher, and nut. What I'm suggesting is another nut, on the OTHER side of the aluminum bracket, to give you something to screw against. The most enthusiastic among us might even want to put a bad of loctite on that "backing nut", but it's probably not necessary.


Among all possible "overheating" fixes, this is surely the easiest -- you don't even need to get near the engine! Don't be like me, and get to this stage only after checking out every single other portion of the cooling system.