Missing Thermostat! 1996 25 hp

I have a recently acquired 1986 25HP ML and in checking the motor I find that it does not (and never did) have a thermostat. How hard would it be to put one on this motor. I understand that some new parts would need to be purchased in order for this to be done. Has anyone done this and did it help with maintaining an idle speed for a longer time without it gumming up. I'm concerned that without a thermostat it will not stay warm enough to idle for long periods of time. It is the only motor on my boat and I really would like to be able to troll with it. In the past I have put out a couple small sea anchors or five gallon buckets to slow me down enough.

GD

Re: Missing Thermostat!

Many people toss 'em out to prevent them from sticking closed and frying the motor. Are you sure the idle adjustment is set correctly? That makes a bigger difference than having a t-stat.

Jeff

Re: Missing Thermostat!

I have great respect for Jeff's opinions, however, in this particular case mine is quite different.

Merc did not install thermostats in their "portable" line (25 horse and under) when they built them - can't really figure why, it maybe saved them a buck a motor by leaving them out.

They SHOULD be installed - a thermostat and a gasket sells for a little over 20 bucks - and is all you need to do the install.

Many believe since they only run their motors in the summer that the water is "warm enough".

Since most outboards like to operate in the 140-175 degree range, unless you are running in water that has a temp of about 100-110 F you probably need a thermostat.

On larger outboards the thermostat will drastically lengthen the life of the internal parts and should always be there.

On smaller outboards, it will likewise increase the life of pistons/rings/cylinders (which is particularly important on 15 horse and under model Merc's which can not be "rebuilt" - if you toast a cylinder, the powerhead is scrap), but it will also greatly improve the idle - particularly in cooler weather.

I put it in this perspective - a new 25 horse 2 stroke Merc (still available in most countries outside the US) sells for close to 3K (all in) - isn't it worth 20 or 30 bucks to protect it and have it run "as designed"?

Re: Missing Thermostat!

t-stat in

why would they install them???

Missing Thermostat Cover!

I'm not sure I made myself clear! The cover on my engine will not accept a thermostat. See the image below; The left half is for Thermostat equipped engines, mine is like the one on the right. Can I get the parts for the left and put them on the right? Clear as mud right!

Re: Missing Thermostat!

I see, yes, you can retrofit it - will all bolt up the same..