Help with cooling issue/head

I picked up a 91 Suzuki DT25 that had overheated. Owner had pulled head and broken off 3 head bolts. I drilled out bolts and rethreaded, replaced water pump and thermostat (old one would not open) cleaned carbs, fuel filter,flushed water passages, new head gasket.

On hose engine would not pee and would start to get hot.
Removed lower unit, hooked garden hose to water pick up tube with lower unit off , engine cools and pees fine.

Put engine in lake, weak, dribbling, pee stream, good water flow from exhaust port, initially, them engine temp continues to climb, (based on leaving hand on head), then water from exhaust port turns to steam and have to shut down. Head is too hot to keep hand on.

I did not machine head at all when I reinstalled it.
When drilling out the head bolts, I got crooked and drilled into water jacket to side of head bolt hole at the bottom of hole. With new head bolt installed, I believe this hole is effectively plugged.

Question: Would a warped head, cracked head, head gasket leak, cause this overheating?
Should I try to seal my mis-drilled hole with epoxy?, rethread and reinstall?
I am leaning toward a warped, bad head, but only a guess.

I don't think it is water pump related, I ran the motor, with the themostat cover off, in the lake and it gurgles good water out of the themostat cover hole when running.

All help appreciated!

Re: Help with cooling issue/head

Just a thought, but have you tried running it with the thermostat not installed...?

I would think the bolt would seal the hole, OR water would leak visibly around the head of the bolt.

A discolored spark plug would signify intrusion of water into a cylinder i.e. a warped head/bad seal.

Until it pees well and water exits well from the exhaust I would guess it is a water pump/flow blockage issue.

Please keep us notified with your progress, I have a Yam 50 with very similar issues and am interested to see what you learn.

Re: Help with cooling issue/head

Just a thought, but have you tried running it with the thermostat not installed...?

Yes, does the same with the thermostat taken out. Plugs look OK

Re: Help with cooling issue/head

Sounds like blockage, this may be a stupid question but did you alighn the water pipe with the pump correctly. Take a 4-6 ft weed eater line and feed it into the pee hole to see if something was stuck in there like metal from the drilling accident.

Re: Help with cooling issue/head

If it was the head you would discolored plugs, and possibly fouled plugs.

Re: Help with cooling issue/head

Any updates?

I would try dropping the LU again and putting the hose to water tube again, just make sure everything is still clear.

If you have good water flow out the pee hole and rear exhaust I would conclude the problem lies with the water pump.

Lastly, a compression tester would prove definitavely that the head gasket seal is good or bad.

Re: Help with cooling issue/head

I have a second 25 HP Suzuki. After fishing season, I am going to switch lower units and see if it fixes problem. If it does, I will be amazed. I replaced everything in the pump when I rebuilt it.