2001 yamaha ox66 over heating

[sako300@]

done a trizillion search. had to replace lower unit with new lu. had good pressure and then went to 0 at idle and about 8 at 4000. running hot after a couple of minutes at idle. new wp, new poppit, new t stats, checked the poppit 3 times, wp at least 3 times and still looks new. have narrowed it down to debris or cracked water tube. question is how do you remove the water tube or check for cracks and how do you clean the water passages other that back flushing..... 2001 ox 66 255 with 650 hrs but runs like a charm.. thanks

Thanks for any help guys

[boats.net]

Will need to remove powerhead to replace water tube and probably need to remove heads, exhaust plate and clean all water jackets.

[sako300@]

pulled the heads today to clean the water passages, and they where not that bad. i hooked the hose to the quick flush to see if i could wash some debris out. water was only coming out of the lower unit, so i turned the hose up on high and i little came out under the port side of the block. should't water come out of the powerhead pretty good are do i have another problem. I have not pulled the exhaust cover as of yet.. what might cause this..

thanks

[Tucker]

Man this is a doozy. It was fine until your replaced the LU? Wonder if the pump is installed correctly? One of those in those internal zincs in the head clogging something up? Never heard of the water pump tube rotting through but guess it could happen. I'd be checking the pump. You said it worked briefly and then pressure was gone. Where is the pressure gauge, back by the stats?

[sako300@]

water pressure on old lu was kinda low, but never ran hot. went to change wp and driveshaft was seized in block, long story short, i ended up cutting the driveshaft and replaced with new lower unit from sei. good pressure from the start and then went down and started running hot art idle. sent back to sei and they replaced water pump, and the same thing when i get it back.the wp seems to be pumping good pressure but it is not reaching the top of the heads at idle. i did remove the lu and hooked a hose to the water tube and had very good pressure that way.. it seems as if something is floating around in the water jacket and stoping up at some point or the water tube is cracked or maybe a gasket.. when i hook the hose to the flush line with the heads off, the water goes down into the exhaust housing instead of up into the powerhead.. same thing wehn it is hooked to the hose, most of the water ends up in the exhaust chamber.... i really don't know how the entire cooling system works, but i am learning a lot with this project...
thanks for the help.

charles

[Tucker]

At idle and low speed the water pressure will not take the water to the heads. That's why you have a PRV. Spring pressure keeps it closed so water can reach the top of the motor. Higher RPMs and water pressure then open the PRV. A bad PRV usually makes an over heat condition at low speeds.

[sako300@]

new prv with spring stretched a little .. new style mushroom prv

[jb123]

was the housing replaced or just the kit ??

[sako300@]

not real sure, but the guy from sei said they replaced the water pump.. i have aanother housing that i might try

[200090tlry]

when you hook up flush port

Your not running the motor I hope. If during the hookup with good water pressure no water comes out tell tale you have a blockage somewhere in heads. Hook it up and let the water run for awhile.

[Tucker]

Please advise status or developments Sako.

[99yam40]

new prv with spring stretched a little .. new style mushroom prv

I believe I read some thing from Rodbolt17 to never stretch the spring, but that should not be your problem.
If it is dumping water then you must have a hole corroded through some where or the PRV is stuck open for some reason

[sako300@]

removed the heads to clean the passage and they where not so bad, so removed the water jacket cover and broke off 7 bolts, so now i am in the process of removing the powerhead to check the water tube, gasket and replace 2 of the bottom bolts in the water jacket cover.. what a pita this had been.. easy out will not remove the bolts, so should i replace with helicoil or stainless inserts..