2000 tohatsu m70c cooling issue

[Bassmaster229]

I purchased a used boat 2 weeks ago. Came with a 2000 tohatsu m70c. The guy said he replaced the water pump and thermostat himself. I ran it twice last weekend. At wide open throttle for extended periods the high temp alarm sounds. I can run 3/4 throttle about 4000 rpm all day with no issues. I have good flow good out the tell tail. Well today I started it in my driveway with the ear muffs on to warm it up before i got to the boat ramp. I noticed water coming from a hole im pretty sure it’s not supposed to. It on what’s called the drive shaft housing maybe? Looking for an idea of what it could be before I tear into. I’m pretty tech savvy. Been an auto mechanic and millwright all my life but never touched marine. Hoping to save a few dollars and tackle this myself

 

[Sea Rider]

Being a 20 year oldie and if used during its entire boating life in salt water expect huge salt formations inside all the water passages which will eventually trigger the audible temp alarm when the motor runs towards max wot rpm range due to poor water cooling, doesn't matter if counting with a new water pump install..

Happy Boating

 

[Bassmaster229]

Being a 20 year oldie and if used during its entire boating life in salt water expect huge salt formations inside all the water passages which will eventually trigger the audible temp alarm when the motor runs towards max wot rpm range due to poor water cooling, doesn't matter if counting with a new water pump install..

Happy Boating

I pulled the foot off today to see if I could determine how the water was making it’s way to the hole in the picture. I also pulled thermostat and the exhaust cover to look for signs of salt deposit. The guy I bought it from used it for stripper and hybrid fishing and supposedly so did the guy he bought it from. But being this boat is 20 years old it’s pretty much safe to say it’s been in salt. But i don’t believe it’s been in it very much. I didn’t see the usual build up of salt behind the thermostat or in the exhaust manifold cover. So I’m not sure if that’s the problem. With the foot off I rigged up my garden hose to the water tube that comes out the top of the pump and ran water through the engine to see if it was coming from somewhere it shouldn’t be. Water only exited the tell tail and the exhaust. So that leaves me to believe that it could of been leaking form the pump itself. Leaking water especially the amount i was seeing could definitely cause poor cooling. The rubber grommet that seals water tube to the pump fits rather loose and I’m thinking that may be it. Also the guy used a bunch of blue RTV on the thermostat. So much that it was restricting the water passages. This could also contribute. I went ahead and ordered a water pump kit, thermostat, and tube grommet. Im going to see if this stops the leaking and see what happens at WOT. Unfortunately the mill I manage just starts it’s annual shutdown Monday so I’ll have to wait 3 weeks to see if the leak is gone or not.

 

[Bassmaster229]

Another question. Is it safe to run compression test with foot off. Like I said in the OP I’m new to marine repair. It runs strong but I want an idea of the engine condition before I start to venture off miles deep into the marsh. I wasn’t sure If it was safe to do it with foot off or not but I would like to test it tomorrow if it’s okay.

 

[Faztbullet]

Is it safe to run compression test with foot off.

Yes...

 

[pvanv]

The water is coming out of a drain hole. Normal.

 

[Sea Rider]

Have you checked the Overheat Sensor condition ? probably shot and triggering prematurely the audible alarm at higher than 4K rpm.

Happy Boating