KAMD43-P overheat

[Wiggo]

Oooh, so after a long time in the wilderness, I'm back. And taking the boat out for the first time in an age, the port lump overheated under load. Fine below 1500 rpm or so, but within seconds of bringing the revs up, the temperature started to creep up.

Checked the strainers (manky, so cleared them), and pulled the impeller, but that was as new. So, does the panel think that I should:

1. check the thermostats, or
2. assume the heat exchanger is blocked and buy in some brick cleaner?

Never having had a problem with heat exchangers before, would I be right in thinking this is a job to be done ashore rather than afloat? Does it involve removing them, or can it be done in situ?

 

[[2068]]

Start with the simple stuff first.
Did the seawater pump prime itself?

Firing up at the dock, the seawater pump faceplate should get noticeably colder to touch as it fills with seawater. A pump face that is getting warmer at idle is not one that has primed. Short term measure would be a couple of pints of water into the strainer, then check the faceplate for wear.

 

[crazy4557]

Get yourself a laser heat gun off ebay or Amazon. Point it all the green bits until you see where the overheat is! Then you can fix that bit, saves that process of elimination.

That's the simple method and easy for me to write, a bit harder for you in practice but those laser guns are brilliant at showing where the potential problem area is.

 

[rafiki_]

I changed the impellers on the 2 Cat lumps in my Snazi recently, had to take the pumps off to withdraw the impellers, but one was leaking anyway, so had to come off for a refurb. The inlet port to both pumps was caked with silt, with a circa 10mm orifice which should have been 35mm ish. If left, these would have caused a significant cooling problem which I dont think would have shown up with a thermal gun, as the water would be cold at this point. No idea if your engine would be the same, but quite easy to find out just by removing the hose where it connects to the pump.

 

[RogerRat]

Oooh, so after a long time in the wilderness, I'm back. And taking the boat out for the first time in an age, the port lump overheated under load. Fine below 1500 rpm or so, but within seconds of bringing the revs up, the temperature started to creep up.

Checked the strainers (manky, so cleared them), and pulled the impeller, but that was as new. So, does the panel think that I should:

1. check the thermostats, or
2. assume the heat exchanger is blocked and buy in some brick cleaner?

Never having had a problem with heat exchangers before, would I be right in thinking this is a job to be done ashore rather than afloat? Does it involve removing them, or can it be done in situ?

Hi Graham,
I don't think you should assume anything for obvious reasons but there has been an extremely large amount of calcium based 'mollusky' growths all last year and late into winter in the Itchen, you can expect heat exchanges to have their water ways blocked at least partially.

Brick cleaning / Rid Lime has to be on the cards.

Good luck,

Roger.