Drilling holes in thermostat to help overheating problem.

[stingraymax]

hello,

i am having some problems with my engine overheating at higher rpm's and only when the water temp is high. ( 99 johnson 90Hp looper)

I have replaced waterpump, thermostats and headgasket but still have an overheating problem.
There is a strong tell tale so water gets around...

I read somewhere on the forum that some people drilled holes thru the thermostats to cool the engine a litle bit more.

Can somebody tell me how I should do this, where to drill and what kind of diameter I should take.

Thanks,

 

[dsinger]

Re: Drilling holes in thermostat to help overheating problem.

I am intersted in seeing how this in done to if you find out and do it will you post a few pics.

 

[freddyray21]

Re: Drilling holes in thermostat to help overheating problem.

i am not an expert, but it seems to me drilling holes in the thermostat would allow a larger flow of water, BUT that motor is running properly should not overheat with the proper thermostat working well it in better to fix the problem of overheating then rigging a solution

 

[Walker]

Re: Drilling holes in thermostat to help overheating problem.

is it a saltwater or freshwater motor. At higher rpms the t-stats should come off their seats and allow water to bypass the t-stats, so I wouldn't blame the t-stats for the overheating you describe.
Are you sure the motor is overheating. Does SLOW kick in?

 

[iwombat]

Re: Drilling holes in thermostat to help overheating problem.

We used to do something similar with stock cars. Just remove the thermostat and replace with a metal plate and properly sized holes. That said, I wouldn't recommend it for anything other than an engine you plan on rebuilding often, or plan on running WOT all of the time. You're likely to run too cold most of the time and risk some really nasty carbon build-up and fuel consumption.

 

[stingraymax]

Re: Drilling holes in thermostat to help overheating problem.

It is a salt water engine but I flush the engine every time with fresh water.

Slow does kick in, with the stats removed no overheating...

 

[Walker]

Re: Drilling holes in thermostat to help overheating problem.

I suggest one of two things.
Pull a head and see if you have any build-up in the water jackets, or put her in a barrel of water just above the water pump. Get the skeg sitting on the bottom if possible. We want to use as little water as we can. Now add 5 gallons of pickling vinegar and run the motor til she reaches operation tem. Shut her off and let cool for 30 minutes or so. Repeat this procedure about 20 times and then try her and see if she still overheats. You can also try something called "Saltaway" but I'm not familiar with its procedures for use.

 

[stingraymax]

Re: Drilling holes in thermostat to help overheating problem.

I will try this thanks for the info.