dt115 overheats at high rpm's

[Happy_Camper]

History; 90's dt115, blew up the motor 2 years ago, bearings went - rebuilt the entire motor. dropped in the water last year, ran like a champ all summer, not a single issue, could pull water skiers (24ft sylvan pontoon). shut it down for the season, my brother (a mechanic) winterized it. Pulled it out this weekend, cleaned it up and dropped in the water. started right up, nice little pee stream at idle at the dock, took it out at low rpm's (2k) ran perfect. after 10 minutes, pushed it up to 3500 and after 5 minutes, the high temp warning sounded, shut it down. popped the cover, it was hot to the touch, and we noticed the pee stream had stopped. put it back on and ran successfully at 2k for 10 min no problems, pushed back to 3k and after a bit high temp light and beeping. shut down, cooled off, took it back to the dock and pulled it out of the water.

my brother thinks;
1. the thermostat might be stuck.
2. the impeller might have broken some fins.
3. something could be clogging water pathways.
4. the water pump might be whacked.

the water pump was replace in the rebuild.

I've searched for thermostat replacement videos for this motor and dont find any. Is there anyone that has a opinion on what to do next? thanks for your help. we wanted to boat this weekend (july 4th!)

[Moonlighter]

I think your brother's ideas are on the money. Start with eater pump and impeller, then check for blockages if nothing untoward found with water pump.

[Solarman]

overheats at higher RPMs, dt115, 140, and many others.

The problem sound just like my two dt140's, and the 115's are just alike.
The exhaust gases were blocking water going into the water pump at higher rpms. Be careful removing the housing, it seals the shaft into the gear case/foot.
Remove the water pump housing and check/ replace the sub water pickup grommets. I found that fixed my prblem with overheating above 2500 rpms.
And make sure you check both ends of the tube, screens and any corrosion that would allow exhaust to get over to the water pump chamber, I had to epoxy the aluminum housing where corrosion ate through just above the pump. Both of my 140's had this same problem. Also, make sure you install the stainless protective plates in correct, they protect the grommets from overheating.
Good luck.

[Happy_Camper]

Thanks for the advice!

i appreciate your responses, my brother ordered the manual, but in the meantime is there anywhere to see a video of the process of removing the water pump? I tried searching and found some generic ones, but not for this motor, or am I asking too much?

btw, Solarman, wouldnt i have experienced that issue with the exhaust last year? we ran at high rpms all summer no issues, I'm trying to understand what could cause that to happen over the winter, and it was a bad winter, freakin 100 below. I'm not a mechanic, but am mechanical enough to understand something changed. thanks again.

[Solarman]

dt115 overheats at higher rpms...

***!! 100 below...chilly!!
Well i'm not a molecular scientist/ or engineer.
You asked where to look, and I gave you a place to check.
Removal of the water pump is simple, under the impeller is a flat plate, and under that should be 4 screws. pry up evenly and the base should slide right up. The sub-water pipe is is right below that stainless plate with the 2 screws holding it down. It supplies additional water needed at higher rpms. There are grommets at both ends of that stainless tube, if either grommets are dry-rotted exhaust will interfere with water pickup at higher rpms.
Could extreme temps cause problems with seals... Ask NASA that question.
Good luck.