Tohatsu 25 hp overheat 4 stroke

[Pinter Boat]

After running for about 10 minutes above 5000 rpm, I get an overheat alarm with rev limit. Dealer read the code and said he thinks the motor is mounted too high on the transom, not getting enough water flow. I have been running this boat for almost 90 hours this season and the problem just started, so I don't have much confidence in his theory, but right now it's all I have. I checked the water pump/impeller = good shape. Tell tale is flowing, thermostat seems to be working. NB. When I shut the engine off and restart, it goes again, no alarms. Any thoughts?

 

[pvanv]

When was the last time a water pump kit (not just the impeller) was changed?
Is this a long shaft motor? What is the actual model/serial?
What temperature has the ECU recorded? What is the water temperature where you are running?
What oil are you running, and what is the level on the dipstick?
Does the surface of the water flow between the splash plate and antiventilation plate when at speed?

 

[Pinter Boat]

Water pump kit was changed at the end of last season along with thermostat. It's a short shaft,model MFS 25B. Tech didn't tell me the actual temp. Water temp where I am running is 85. Oil = mercury four stroke 10 30 FCW. Reads full on dipstick. I have to check about the flow between splash and anti-ventilation plate.

 

[Sea Rider]

With OB sitting at 90? and weight well deck distibuted, go for a wot spin on flat calm no wind water cond, make a close tight turn at speed and plane and check if prop aereates, if so, lower OB on transsom till aeration disappears. Is it a clamp or unclamped OB version ? Ideal transom height is for water flow to pass skimming right under upper small water deflector plate.

Happy Boating

 

[Pinter Boat]

Thank you Sea Rider. Will report back.

 

[Sea Rider]

Thank you Sea Rider. Will report back.

This is the ideal transom height for any Tohatsu OB,



Can visually check it out by sitting on deck, seat next to transom and pulling your head out transom while at a straight water course. When you dial that precise setting OB will work fantastic well in any water cond along nice close tight turns at speed.

Vid : https://www.youtube.com/watch?v=oBeZjaA76VM

Happy Boating