98,150 omc,running hot

[bwhit]

I've had a ongoing problem with my1998 150 ocean pro running hot for about 3 years,will make a change ,like water pump,thermostat,work for a time or two,then overheats again.(horn sounds) It only overheats above 3/4 throttle,only have a guess of 100hrs on motor.This is what has been done to it,thermostats replaced,water pump replaced,heads removed,soaked and cleaned,power head removed,just had plastic bowls on carb replaced,leaking and would not go over 4100 rpm then would miss.just replaced plugs,no help,put thermosts in hot water with fish therm,they work.So running out of money on this motor,added alittle extra oil to gas to see if that would help. some people tell me to pull the thermostats out and run it full throttle and see if the horn goes off???will it hurt to try that?? oh yea and my pressure is about 7psi at idle and 20 to 27 at 3/4 to full throttle///running about 3 or 4 minutes and hot alarm goes off,also had sensor replaced 2 years ago, I think thats most every thing and would appreciate any advice you can give,thanks again

 

[clanton]

Re: 98,150 omc,running hot

Pull the gear case and look at the waterpump housing, if the plastic housing has vent in the side, you have wrong waterpump. Tattle tale stream should be realy strong, like 30 lbs at 1500/2000 rpms. 7 lbs at idle not enough. I not sure about this, but most vented pump housings are white plastic, some of the older one were black. The miss at 4100 is probley the power pack.

 

[Dhadley]

Re: 98,150 omc,running hot

After you follow Clantons advise lets look at a couple of things. Since you did not say that its going into SLOW when the horn sounds lets verify that it is indeed overheating.<br /><br />This can be verified with an infer red gun like a Ray Tec.<br /><br />Describe a little further about the horn. When it sounds and you reduce throttle, how long does it stay on after you reduce throttle (with the motor still running)?<br /><br />What spark plugs are you running?<br /><br />Tell us more about your boat and set up. Jackplate?

 

[bwhit]

Re: 98,150 omc,running hot

1998 150 omc running hot/// I am running ngk4551 BR9HS-10 plugs I also tried Champion 938 QL78YC,when the horn goes off I pull it back and usually takes 2 or 3 minutes to clear,my presure sometimes at idle is 10 and full throttle 27 which is about the best Ive ever gotten and that got better after the power head is removed,it runs great until the horn blows,what about removing the thermostats would it hurt to try that?

 

[Dhadley]

Re: 98,150 omc,running hot

#1 -- we need to get Champions back in the motor. Period.<br /><br />Did you get a chance to look at the pump to answer Clantons questions?

 

[bonitoman]

Re: 98,150 omc,running hot

Ngk's are great in Yamaha. In an OMC engine "Champion" should be the only word in your vocabulary. I would also put in a cooler plug than the QL82's

 

[bwhit]

Re: 98,150 omc,running hot

I have not been able to drop the foot yet,boat hangs in boat house,had alot of rain,ramp a little boggy. would like to try all other option first that dont require me to take boat out.Which champion plugs (cooler) do you recommend? Ihave ql78ycare thet to hot and what about removing the thermostats,not for a long term fix but to see if it makes a difference?Could their be restriction some where that is a small amount causing this problem,I read some where on forum that someone uses lime away to flush motor and said it took care of his overheating problem,have you ever heard of doing that? I appreciate all ya'lls help,thanks, bwhit

 

[hookedonjc]

Re: 98,150 omc,running hot

Hey Bwhit <br />You need to get a service manual and dont pay someone to pull that foot off you can do that. <br />Champion plugs are best and factory recomended. <br /> Hookedonjc

 

[seahorse5]

Re: 98,150 omc,running hot

Are there any transducers, speedo pickup, or thru hulls within 14" of the centerline of the motor? If so, you may be ingesting air bubbles which do not cool the motor very well.<br /><br />Also the correct pump kit is very important, use the whole model number when ordering parts. Clanton is correct about the housing colors.