115 omc overheating need help!

[Rhammer]

I have a 15' whaler with a 115 v4 , i have changed the head gaskets and diverters, put new thermostats in twice and even left them out for a while and it made no difference it still overheated, i have replaced the relief plug, ball and spring also, it only overheats at high rpm's . if i take it slow or idle its fine. motor runs good, i have checked head temps and the temps stay even on both cylinder banks. i am going crazy trying to figure this out. any help would be greatly appreciated.

 

[Joe Reeves]

Re: 115 omc overheating need help!

You've said nothing of the water pump. Have you replaced it? If not, do so.

 

[boobie]

Re: 115 omc overheating need help!

When you have an overheat problem the first thing you go for is the throat. And that's the water pump.

 

[emdsapmgr]

Re: 115 omc overheating need help!

Agree. If/when you replace the impeller, visually check the water passage in the lower unit-from the water intake screens to the underside of the water pump. Have you pulled the cylinder head covers off to inspect the water passages for any restrictions?

 

[Rhammer]

Re: 115 omc overheating need help!

Agree. If/when you replace the impeller, visually check the water passage in the lower unit-from the water intake screens to the underside of the water pump. Have you pulled the cylinder head covers off to inspect the water passages for any restrictions?

i apologize for not clarifying i have the turbojet model with the impeller + housing setup. i have replaced the relief plug and ball and spring in the impeller housing. i have removed head covers and heads and all was clean with diverters in good shape. i'm a little lost at this point. don't know what to check next.

 

[boobie]

Re: 115 omc overheating need help!

That's why it's always nice to post a model #.

 

[Surgeevg22]

Re: 115 omc overheating need help!

Does it overheat on a hose, or just on the lake?

 

[SKEETR]

Re: 115 omc overheating need help!

What oil mix are you running? Is this a new boat to you, did it used to run well but is now having this problem?

 

[Rhammer]

Re: 115 omc overheating need help!

Does it overheat on a hose, or just on the lake?

it does't overheat on the hose ,and when i'm out on the water anything from mid rpm's to low speed is fine, its just overheating after i run at high rpm's 4,000 or more for about 5 to 10 minutes.

 

[Rhammer]

Re: 115 omc overheating need help!

What oil mix are you running? Is this a new boat to you, did it used to run well but is now having this problem?

i'm still using the VRO with johnson oil. i have noticed that at idle it started smoking more than usual. i've had the boat over 10 years and rebuilt the motor earlier this year, i have over 10 hours on the motor and then all of a sudden it has started overheating at high speeds. i pulled heads back down, checked diverters, and replaced thermostats again. i just can't find out whats going on here.

 

[boobie]

Re: 115 omc overheating need help!

Is it getting enough water from the jet pump. Maybe a blocked line or build up of corrosion ??

 

[halfmoa]

Re: 115 omc overheating need help!

A new thermostat is a wise purchase also.

 

[SKEETR]

Re: 115 omc overheating need help!

i'm still using the VRO with johnson oil. i have noticed that at idle it started smoking more than usual. i've had the boat over 10 years and rebuilt the motor earlier this year, i have over 10 hours on the motor and then all of a sudden it has started overheating at high speeds. i pulled heads back down, checked diverters, and replaced thermostats again. i just can't find out whats going on here.

You might try premixing your gas and disconnecting the vro to see if that may be part of the problem. I know I have seen the procedure here somewhere but it is not hard to do.

Do you have a water pressure gauge on the helm and is there a good stream of water coming out of the pee hole?

My gut feeling is that the motor may still be tight from the rebuild and you need to ensure it is getting adequate oil for a while. I'd double the mix for another 10 hours and just mix in the tank to make sure the vro is not cutting out for some reason.

 

[Rhammer]

Re: 115 omc overheating need help!

You might try premixing your gas and disconnecting the vro to see if that may be part of the problem. I know I have seen the procedure here somewhere but it is not hard to do.

Do you have a water pressure gauge on the helm and is there a good stream of water coming out of the pee hole?

My gut feeling is that the motor may still be tight from the rebuild and you need to ensure it is getting adequate oil for a while. I'd double the mix for another 10 hours and just mix in the tank to make sure the vro is not cutting out for some reason.

do you think there could be a relationship between the overheating and the excessive engine smoking ? they did start happening about the same time. i have run the double oil on the 10 hour break-in. the first overheat i had i believe i was still running double oil. as far as the pee hole goes, this boat has it plugged off and everything runs through a muffler and adapter assembly, waterflow does seem good out the muffler + assembly ( jet drive ) can a vro cause an overheat condition ?

 

[Rhammer]

Re: 115 omc overheating need help!

Is it getting enough water from the jet pump. Maybe a blocked line or build up of corrosion ??

it sure seems like it is, i've been all through this motor and can't find any water restrictions?

 

[SKEETR]

Re: 115 omc overheating need help!

Yes overheating can be caused by multiple things.

On the pressure issue, you have no means to tell if the jet pump is pumping water eh? That would be the next thing on my list to get that hose unplugged and reconnected so you know tell these things.

The only other place I can think of that could be blocked is the passage from the impeller to the check ball. You are gonna have to pull apart the jet again and pull the ball out and snake a bent hangar or wire down that one. May just be a pebble wedged in there.

 

[Rhammer]

Re: 115 omc overheating need help!

Yes overheating can be caused by multiple things.

On the pressure issue, you have no means to tell if the jet pump is pumping water eh? That would be the next thing on my list to get that hose unplugged and reconnected so you know tell these things.

The only other place I can think of that could be blocked is the passage from the impeller to the check ball. You are gonna have to pull apart the jet again and pull the ball out and snake a bent hangar or wire down that one. May just be a pebble wedged in there.

I've had that pressure relief ball + spring out and replaced them with new. as far as the plug in the exhaust plate ,i have the bubble back exhaust, i can not get the plug out, i can't get a torch in that area on this boat to heat it up. it appears to be a stainless steel hex head plug. at least if i can remove the plug i could attach a nipple and hose to see what kind of water flow i had at high speeds. one other thing i checked the plugs and they don't look like i thought they would from running double oil, they are fairly clean, insulator is light brown. thanks for all your help, do you still think i should continue to run double oil ?

 

[Surgeevg22]

Re: 115 omc overheating need help!

What I would also check to make sure is that one of the fins on the impeller housing (not the actual impeller) itself is not broken. Mine has a broken piece. I can see where a broken impeller housing fin can divert water away from the cooling system pickup. Highly unlikely but it may be worth checking if all else seems to be ok.

 

[durban]

Re: 115 omc overheating need help!

are you sure your cylinder head gaskets are fitted the correct way if you gonna run your motor whit deflectors in , other wise go plan B

 

[SKEETR]

Re: 115 omc overheating need help!

I've had that pressure relief ball + spring out and replaced them with new. as far as the plug in the exhaust plate ,i have the bubble back exhaust, i can not get the plug out, i can't get a torch in that area on this boat to heat it up. it appears to be a stainless steel hex head plug. at least if i can remove the plug i could attach a nipple and hose to see what kind of water flow i had at high speeds. one other thing i checked the plugs and they don't look like i thought they would from running double oil, they are fairly clean, insulator is light brown. thanks for all your help, do you still think i should continue to run double oil ?

I understand that you replaced the ball and spring but that check valve releases excess pressure. Did you inspect the ball seat to ensure it is clean and free from any corrosion? Flashlight req. If it looks bad a large drill bit turned by hand will clean it up. When you replaced it did you check the ports in the impeller assembly? You cannot see the intake unless you have the impeller removed. Not that you need to do that but from the check valve you can snake a wire down and free any obstructions if there are any. It would be one of the possibilities of a blockage that would not be noticed as when you run on the hose you bypass this intake.
On my setup the nipple coming off the bubble back feeds a line that goes to a water pressure gauge. The pee hole hose is connected to the port side of the adaptor underneath.