engine stat

[andreworiordan]

Hi, I recently bought a 10hp 2003 Mercury 2stroke engine, she is a long shaft tiller controlled model, I have ran the engine and found that the stat isnt working and the water is coming out boiling, i removed the stat to confirm it was not the impeller, sure enough it few through and runs fine now, Can i leave the stat out or am i better off replacing it? I have a 15hp engine that i have for spare parts, I went to take the stat out of that one and found there was not one there, so again can i run the 10hp without a stat? thanks!

[Boats&Outboards]

People often remove them as with that model it does not have a constant flow of water, rather it pumps when the stat opens as required then stops. The problem with that is your forever worried when you take a look and see nothing coming out.

Not sure of the risks running without but I'd suggest replacing it with a restrictor plate. Basically that can be a washer with it's hole drilled out to allow a constant flow but not too much to allow it to cool too much.

Peter ~ Boatsandoutboards4sale ~ askboatsandoutboards4sale@sky.com ~ 07930 421007

[Fenlander]

I have the 15hp Mariner from 2001 which is a very similar model to yours. The advice B & O gives will get you up and running cheaply and will be fine. I'm a bit of a by-the-book guy so in the same circumstances I bought a new stat. Cost about £40 inc post though.

[Boats&Outboards]

Originally Posted by Fenlander

I have the 15hp Mariner from 2001 which is a very similar model to yours. The advice B & O gives will get you up and running cheaply and will be fine. I'm a bit of a by-the-book guy so in the same circumstances I bought a new stat. Cost about £40 inc post though.

It's not advice. It's just experience of how they come in to me. I'd always suggest running as per manufacturer specifications but I know people do prefer a constant tell-tale rather than not

Like you say cheap enough to replace. Each to their own I guess

Peter ~ Boatsandoutboards4sale ~ askboatsandoutboards4sale@sky.com ~ 07930 421007

[Fenlander]

Hope you didn't think I was saying you were wrong Peter... just giving the alternative option. No doubt the variable tell tale via the stat on this model is a pain to keep an eye on.

[Boats&Outboards]

I know don't worry just did not want people thinking I'm suggesting to "bodge" things up that's all

Peter ~ Boatsandoutboards4sale ~ askboatsandoutboards4sale@sky.com ~ 07930 421007

[uncle al]

your obm will run cold with a risk of glazing the bores because the fuel mixture hasnt been completely burned,it will not run as eficiently either

[Courageous]

As Al says - FWIW I advise with thermostat or nothing at all. If you start playing with orifice plates how will you "guess" the size of the hole? Before you know it you'll have a cracked block!

[Searider]

I couldn't believe the cost of outboard thermostats.

Just bought a secondhand 4hp Yamaha 4 stroke and thought that it the thermostat was cheap i'd replace it as a precaution - Nearly £50 though!
Tested the old one and it was fine, so happy.

[9D280]

The 50 / 60 clamshells seemed to get it removed as part of the factory build! The thermostat dissappears from the microfiche for the last three or so variations!

I would agree with Uncle Al ref. the running cold, but I reckoned that if Merc removed it, then they presumably must have tested before doing so, and as my boat spends most of it's time either moving... If I am helping out as a rescue boat I give the starter quite a lot of exersise, which also saves a bucketload of fuel.

The only real difference I've noticed to operation since I removed it is that I need to use the fast idle lever for 1 min or so on a cold start & 10 - 15 seconds on a warm start as opposed to not needing it at all.