Tohatsu 8 Hp 1993 2 Stroke Model # M8b Thermostat Question

[davio47]

I just bought this motor. This motor sat in a basement for 3 years. I have run it in a barrel and it runs nice. The motor exhibits a strong flow of water from the rear port and indicator tube. The water pump seems to be working fine. This motor was used primarily in the Chesapeake Bay on a Dingy. My concern is the possible corrosion in the water jacket and its effect on the thermostat operation. Is this something I should be concerned about and pull the head and replace it? If the thermostat fails or clogs would this cause a over-temp condition? If fails would it usually fail open? Interested in your thoughts on this.
Thanks,

Dave

 

[pvanv]

Re: Tohatsu 8 Hp 1993 2 Stroke Model # M8b Thermostat Question

Yes, the stats usually fail open.

If it overheats, suspect pump problems first, then proceed to troubleshoot the cooling passages if that's not at fault.

 

[davio47]

Re: Tohatsu 8 Hp 1993 2 Stroke Model # M8b Thermostat Question

Thanks, it seems to be cooling and pumping water fine. What would be the primary indicator of an overheating condition, other than smoke and heat?
Thanks

 

[pvanv]

Re: Tohatsu 8 Hp 1993 2 Stroke Model # M8b Thermostat Question

If the telltale is squirting, you're probably OK. If the motor is too hot to even touch briefly, that's unusually hot. In the extreme, the motor would slow down and seize.

Testing is done with special crayons, which have specific melting temperatures, or with an IR thermometer gun.

 

[davio47]

Re: Tohatsu 8 Hp 1993 2 Stroke Model # M8b Thermostat Question

Thank you so much for your very knowledgeable information. I feel comfortable now that it is cooling as it should. I love this motor, its simple to work on and it runs beautifully.
Thanks