Merc XR4 running hot!

[bjcrawfo]

Runs hot only when running full throttle for about 5 minutes or so. I have replaced water pump, and poppet valve. Checked compression. 120 -121 all the way around. Water psi at wot is 12 - 15 psi. When the motor is at idle its not showing any water pressure. After I run down the river a ways and stop the tell tale is only spitting water, not even a consistent full stream. Any help would be appreciated.*

[transomstand]

When you say new water pump, what did you replace?

[bjcrawfo]

everything. housing, base... whole nine yards

[transomstand]

Did it help at all?

[bjcrawfo]

No. thats what led me to changing the water pump and poppet valve.*

[davemvegas]

i would check thermostats on upper end of each cyl head. i have noticed mine 91 200hp 2.5 did not squirt water until it built a little temp and thermostats opened. if corrodid a little they might be restricting water flow. you would still have good water pressure.

[bjcrawfo]

forgot to mention new thermostats as well.*

[Bayou Native]

I had the same thing happen last year, it was a broken head gasket.

[bjcrawfo]

I had the same thing happen last year, it was a broken head gasket.

And the compression was ok?

[transomstand]

Things to look for next.

Restriction before the water pump
Split/leaking water tube or seals
Powerhead base gasket
Head gaskets

[ChrisCarsonMarine]

Are you sure the grommet is in the pump housing under the guide tube?

[bjcrawfo]

Are you sure the grommet is in the pump housing under the guide tube?

Does this grommet go at the base of the guide tube? Meaning does it fit into the water pump housing?

[transomstand]

Yes. there is a rubber seal in the top of the water pump housing, and one in the adapter plate.

[bjcrawfo]

Okay. I'm sure I have found the issue. I have narrowed it down to the the pan gasket. I'm fixing to ask a stupid question here, so please forgive me! The pan gasket and the exhaust gasket are the same thing right? I have never taken a power head off. How hard is it? Thanks for the help.

[transomstand]

Easy. 10 nuts off the powerhead studs, disconnect shift shaft lever, lift it off.

[bjcrawfo]

Is all I need a base gasket? Or did I need to purchase anymore gaskets?

[transomstand]

Just the base gasket

[bjcrawfo]

Update. I've changed the power head gasket and also changed the exhaust plate gasket. Still running hot at wot.. So I pulled heads and no blockage and replaced head gaskets. Still running hot. I have right at 15 psi of water pressure at wot. Motor is running good, and water coming out of tell tale is good. I'm lost. I'm only taching 5200 at wot... Would the wheel being to big cause it to run hot? Or maybe a bad alarm or something?

[luckybuff]

Update. I've changed the power head gasket and also changed the exhaust plate gasket. Still running hot at wot.. So I pulled heads and no blockage and replaced head gaskets. Still running hot. I have right at 15 psi of water pressure at wot. Motor is running good, and water coming out of tell tale is good. I'm lost. I'm only taching 5200 at wot... Would the wheel being to big cause it to run hot? Or maybe a bad alarm or something?

My 86' 175hp stock is running hot too, sometimes. Someone told me but I have not checked the water tube, "tube form water pump to the base of the power head" for a split in the tube. I hope to find time to check this. You may want to do the same.

luckybuff

[bjcrawfo]

My 86' 175hp stock is running hot too, sometimes. Someone told me but I have not checked the water tube, "tube form water pump to the base of the power head" for a split in the tube. I hope to find time to check this. You may want to do the same.

luckybuff

I have replaced the water tube as well.

[luckybuff]

I have replaced the water tube as well.

Do you have diverters in the block. Well known SNF vendors have installed short peices of 3/8" rubber hose to divert water flow around each cylinder, so water would be diverted before leaving the block. Some add two and others four peices of hose, but they cut the ends 1/4" short, from the top. Do a search for "diverters" (here on SNF)if my memory is correct. Then you will see what I am describing. I am just a 2010 newbee.

luckybuff

[tlwjkw]

Did you "split the adapter" plate, check gasket and/or junk in there after pulling tha PH? Chunk idle/advance module and reset timimg just because? Diverters help but arn't necessay for that motor. Have you checked for "really" getting hot or you just goin' by tha horn going off? Any kinda temp guage? By feel?.......... Those things seem ta be tha only thing that I can think of. But hell, its a Merc. Ha!

[bjcrawfo]

Ok. I hooked temp gauge up, and its still running hot. Remember this motor has a Bobs L/U on it. I have lowered it a lot just to try and get the water psi up. Motor stays cool while idling, but as soon as i put it in gear and blast off the temp starts climbing and at wot im only seeing 10 - 12 psi of water pressure. Has a complete new water pump assembly, new head gaskets, new base plate gasket, and exhaust plate gasket.