Overheating saildrive
QI have a Westerly Spirit fitted with a Volvo Penta 10hp and saildrive.
I moor the boat on a swinging mooring in the Dee Estuary which has a very soft sand/clay/mud bed on which my boat sits when the tide goes out.
Occasionally the saildrive will dig into the sea bed but never deep enough to cover the upper vents. They are, however, prone to being blocked with barnacles which I clear once a month.
I recently stripped down the saildrive to replace the main seal and clean it out after a bad season of overheating last year.
I replaced the thermostat and impeller, and thoroughly cleaned all the ports on the engine and saildrive.
On my second trip out this year after lockdown the heating alarm was triggered once again. If I take the revs off, leave it a few seconds then apply the revs again the alarm goes off for a short while then returns. Sometimes full throttle will switch the alarm off but then it returns quicker.
What do you think is the problem?
I’ve now fitted an emergency pipe with a bypass valve that I could use to draw water from a bucket.
Will bypassing the saildrive with the lack of coolant damage it?
Could I fit a through-thehull fitting and bypass this altogether? Roy Sheriff
STU REPLIES:
These sail drive units do have a problem with beasties growing in the internal waterways. However you’ve said you’ve cleaned yours out so that shouldn’t be the problem in this case.
Friends of mine with similar torubles have actually taken the drastic step of blanking the ports off and taking the sea water pump intake off one of the other through hull fittings or installed another through hull fitting and so bypassing the troublesome water gallery in the leg altogether – much the same as you suggest.
Assuming that this engine is an MD2010 I’d first check that the heat exchanger end where the raw water goes into the engine from the pump isn’t partially blocked with old broken pump impeller bits etc.
Basically you have to determine whether the issue is a blocked gallery in the leg or a blockage somewhere else in the cooling water circuit.