inboard engine

[robbo1973]

i have just replaced an inboard engine on my boat. like for like. it is an escort mk1 mexico 1600 engine. when i took the old one out, i never checked to see if there was a thermostat fitted. when i fitted the replacement engine, i also fitted a new thermostat. but i have been told that you shouldnt fit the thermostat, as the engine can never get up to pressure to open it fully and may damage the head. any advice would be great

 

[tillergirl]

A thermostat enables an engine to get up to a working temperature - i.e. it restricts the flow of cooling water until the engine is hot enough to open the thermostat. Its an issue of temperature not pressure. I would leave it in!

 

[Bunny]

If a thermostat is not fitted the engine cannot get up to normal operating temperature, this will use more fuel and also cause condensation inside the engine, eventually emulsifying the oil. I would leave it in.

 

[robbo1973]

thanks for the above advice.
another thing. is it natural for the engine to throw alot of steam out of the exhaust. i have noticed that some people add pipes to the end of the exhaust to semmerse in the water. is that a good idea. it just looks quite bad, when i am going up the river and it looks like smoke bellowing out the exhaust.

 

[Norman_E]

That is not an engine often used in boats, how is it cooled? Is it cooled directly by water from the sea (or river) being pumped through its cooling system, or indirectly by sea water being pumped through a heat exchanger to cool the engine coolant? If it is the former the thermostat may be restricting the flow through to the exhaust and causing it to get too hot, thus boiling the cooling water that is getting through. You should have a good flow of water coming out the exhaust (often in spurts rather than continuously).

 

[Ramage]

That motor is usually marinised as a Watamota Sea Tiger.

 

[robbo1973]

it is pumped directly from the river through the engine to cool it

 

[Norman_E]

In that case try it with the thermostat removed, as it may be reducing the flow too much, and see if you get more water and less steam out of the exhaust.
Let us know the results. If that does not solve the problem there may be someone here who can offer further advice.

 

[Lakesailor]

A closed circuit cooling system builds pressure by design as it's a closed loop and the already heated water recirculates around the engine until the thermostat opens and allows the water to the cooling device - radiator or intercooler.
The point about the pressure is that it raises the boiling point of the water so vapourising doesn't occur at the temperature the system is designed to run at.
With raw water cooling it's unlikely that a pressure can build up as it would bleed back through the water pump. Hence the heat range of your thermostat would be very important as it may not open early enough to prevent water vapourisation in the cylinder head and possible vapour (steam) lock. This would create localised hotspots in the cylinder head and cause problems. If you are going to fit a thermostat it needs to be a much lower temperature range than the car specification.
Good luck as whenever I try to buy a part for a project I meet a stone wall of "yes, but what model car is it for?" it seems that the wonder of databases doesn't allow searches on things like size or heat range etc.
For instance if you want a lower temp thermostat for a Mini you need to ask for an old Mk11 Jag thermostat as they are lower temp ones.
If you decide not to use a themostat it's often a good idea to use the mounting plate for the thermostat valve, just cut the valve off, as the restricted opening of the plate can provide swirl in the cylinder head to scavenge pockets of hot water. If there is no restriction there will be an "easy" route for the water to flow through the head, leaving overheated water in the hard-to-reach corners.

Quote from a specialist kit car manufacturer

"Do not on any account remove the thermostat, as that will cause the rear pistons/cylinders to overheat with eventual piston failure. There is a restrictor plate that replaces the thermostat, available from Mini specialists and used on racing “A” series engines."

disclaimer: Most of these comments refer to Mini engines, but can't see why the theory doesn't transfer to Ford Kent engines. (but their heads are fundamentally different in that they don't have combustion chambers in the head)

 

[Avocet]

I think the Mini advice is peculiar to A-Series because of the way the galleries are cast in the block - same with Ford's V6 "Essex" engine (I'm told)! There's no particular reason why it would be the same on any engine.

As far as the thermostat thing goes though, surely there is a bypass somewhere in the system? The water won't stop circulating round the head, block and heater matrix just because the thermostat is shut will it?

If it were my engine (and most DEFINITELY if it went anywhere near salt water!) I'd be inclined to make it a heat exchanger and run it like a car engine (normal thermostat etc) and let the heat exchanger dump the heat back into the river. That way, you can run it (the heat exchanger) as cold as you like and the engine will be working as designed. Presumably, being a car engine, it has no sacrificial anodes and (probably) some quite small water galleries which could end up getting blocked?