Can an 8 hp function effectively without a thermostat?

displaced47 · Oct 17, 2012

Hi all,

I have an ancient (1971/1972) yamaha 8A with a Mariner decal and I just checked and there is no thermostat.

Must it have one?

What difference will running without make?

I live in the tropics so cold weather running is not an issue.

thanks

robert graham · Oct 17, 2012

Re: Can an 8 hp function effectively without a thermostat?

The thermostat is an important part of the cooling system, so I'd say the motor is either going to run too cool or too hot....either way is not so good. Hopefully look around on-line or at boat shops for a thermostat that might fit...

ShinnecockMatt · Oct 17, 2012

Re: Can an 8 hp function effectively without a thermostat?

displaced47 said:
Hi all,

I have an ancient (1971/1972) yamaha 8A with a Mariner decal and I just checked and there is no thermostat.

Must it have one?

What difference will running without make?

I live in the tropics so cold weather running is not an issue.

thanks

Use only in an emergency without a t stat. Motor will run too cold thus inefficently and there's always the possibility of a cold seize scenario.

stylesabu · Oct 18, 2012

Re: Can an 8 hp function effectively without a thermostat?

there is a reason it came with one. a cold motor wastes fuel. besides you need the restriction

displaced47 · Oct 18, 2012

Re: Can an 8 hp function effectively without a thermostat?

stylesabu said:
there is a reason it came with one. a cold motor wastes fuel. besides you need the restriction

That being said - if the thermostat that is listed on the parts list is obsolete and not available anywhere how much variation is there in others? Could a different one do the job?

stylesabu · Oct 18, 2012

Re: Can an 8 hp function effectively without a thermostat?

there has to be a replacement available.your motor isn't that old

displaced47 · Oct 19, 2012

Re: Can an 8 hp function effectively without a thermostat?

stylesabu said:
there has to be a replacement available.your motor isn't that old

I have looked everywhere and they do not appear to be available... the motor is a 1971/1972 made for Mariner by Yamaha before Yamaha launched in the US Market...

If you have any ideas I would appreciate them! I wonder how much variation there is in thermostats anyway they all look the same to me!

matt167 · Oct 19, 2012

Re: Can an 8 hp function effectively without a thermostat?

It is obsolete.. Most of the motor is obsolete according to another site ( checked every serial range ). Not much you can do. Only thing that I can say is run it by Yamaha and see if they can get an equivlant thermostat.. Otherwise, run it till it pukes and be prepared to get another OB. Everything I checked is obsolete except for a few small parts.

Silvertip · Oct 19, 2012

Re: Can an 8 hp function effectively without a thermostat?

Remove the thermostat housing and measure the diameter of the cavity where the thermostat flange sits. Now head to your nearest farm supply store or auto store and measure thermostats. Find one that is the same diameter or slightly larger and the temp range you need. Grind down the flange until it fits. Go boating. Be aware that auto thermostats will be 160, 180, or 195 degrees. You will likely need a 160.

displaced47 · Oct 20, 2012

Re: Can an 8 hp function effectively without a thermostat?

matt167 said:
It is obsolete.. Most of the motor is obsolete according to another site ( checked every serial range ). Not much you can do. Only thing that I can say is run it by Yamaha and see if they can get an equivlant thermostat.. Otherwise, run it till it pukes and be prepared to get another OB. Everything I checked is obsolete except for a few small parts.

Yep it's really hard - there is a VERY expensive UK site that sells some of the parts. I did manage to get an impeller through ebay (from the UK) I bought two so I would have a spare too but there was no way of getting any of the other water pump parts...

displaced47 · Oct 20, 2012

Re: Can an 8 hp function effectively without a thermostat?

Thanks Silvertip that sounds like a good idea.

EddiePetty · Oct 21, 2012

Re: Can an 8 hp function effectively without a thermostat?

Failing locating the proper thermostat, procure a stainless steel flat washer, file fit the outside diameter and adjust the inside diameter to provide back pressure (slows the water flow to allow dissipation of heat into the water). An IRThermometer aimed at the water jacket will assist in adjusting the flow rate.

Can an 8 hp function effectively without a thermostat?

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