1989 135 hp mercury overheating at mid range

[viking1761]

hello Im viking1761 a new menber.Im having a problem this motor runs good but it overheats only at mid range not at low or high.changed water pump and thermostad and poppit vavule no result pleas help.

 

[andy6374]

Re: 1989 135 hp mercury overheating at mid range

Sounds like the poppet is either opening too late or too early.

 

[viking1761]

Re: 1989 135 hp mercury overheating at mid range

Sounds like the poppet is either opening too late or too early.

tThanks ,how can I adjust this vaulve its new I dint see any way to adjust it.:javascript:;
:'(

 

[Texasmark]

Re: 1989 135 hp mercury overheating at mid range

How do you know it's overheating? Does the high temp sensor close and the solid alarm sounds then goes off if you slow down or speed up?

Never heard of such a thing.

At low speed, cool/cold temperatures, the thermostat and pressure relief stay closed causing the engine to warm up. At approx 120F the thermostat starts opening regardless of the rpm's. By 130F it should be fully open.

The pressure relief valve is pressure driven. So, if you drive your boat forward with significant speed, regardless of the temperature, sufficient pressure (as a result of your forward speed) will cause water to enter the water pickup tubes in the lower unit of the engine.

This pressure will force the pressure relief valve off it's seat and bypass the thermostat and the volume is like 4 or so times the volume of the water going through the thermostat. You will have immediate cooling and if your stat was your problem your horn will go off in a matter of seconds. BTDT

So, I don't understand the root cause of your problem.

Mark

 

[viking1761]

Re: 1989 135 hp mercury overheating at mid range

Yes the horne goes on when Im at 2000rpm and if I slow down, it starts to cool off or if I speed up . no body seems to know. I saw in another web page a guy had the same problem with the same motor and with sea ray. He is still searching too.I think is somthing in the head stuck inside.Its driving me crazy

 

[viking1761]

Re: 1989 135 hp mercury overheating at mid range

I have good water preasure all througth the rpm range. water from the pee whole is very hot, I have measured it with a turkey temperature gauge and it reading as my boat gauges.

 

[phatmanmike]

Re: 1989 135 hp mercury overheating at mid range

poppet valve

 

[gss036]

Re: 1989 135 hp mercury overheating at mid range

Do you have a water pressure guage, if so what is the pressure at idle, mid range and 4000 rpm & above?
The thermostats should open at 143 degrees. Then poppet opens at about 2500-3000 rpm, if you have a pressure guage, you should see some fluctation when(if) the poppet opens.
When you changed the poppet, did you change all the components?

 

[Texasmark]

Re: 1989 135 hp mercury overheating at mid range

Poppet, pressure relief, guess we are talking about the same critter.

Thinking more about it, if the poppet is slow to come off it's seat then the engine could develop enough heat to blow the horn. My OT horn goes off at 195F so that is getting very hot.

Sounds like it (the poppet) needs to be dismantled and looked at. Since it is late coming off I would think that either the rubber valve part is sticking (for some reason) and/or the spring (that keeps the valve seated) is stiffer than it is supposed to be...............or maybe there is some crud build up, like between the windings of the spring that interferes with it opening normally.

HTH

Mark

 

[viking1761]

Re: 1989 135 hp mercury overheating at mid range

I changed all parts .it had some crud , I cleanded before Istaling the new one ,spring,diaphram. can I run the engine withuoght this poppet vaulve. I need to check the water preasure. It comes out pertty strong .

 

[Texasmark]

Re: 1989 135 hp mercury overheating at mid range

Problem with that is that you need to keep the powerhead full of water. I have run my 3 cyl 90 hp with the thermostat out for a period due to a frozen closed stat, but that hole is much smaller than the poppet.

After listening to more informed folks on this site, I went ahead and installed a new one.

Mark

 

[KCLOST]

Re: 1989 135 hp mercury overheating at mid range

When you changed all the parts, did you also change the carrier and grommet that fits into the hole in the block?

Your symptoms make me thing that the poppet is not seated good enough at 2000rpms... At that rpm it should be closed.

What are your water pressures at idle just at start-up and also after the t-stats have opened, 2000rpms, and WOT?

 

[gss036]

Re: 1989 135 hp mercury overheating at mid range

I was thinking the same thing last night, but was waiting for an answer before suggesting the carrier and grommet.
DO you have a water pressure guage installed on the engine?

 

[imported_tunaman]

Re: 1989 135 hp mercury overheating at mid range

hey viking im a new member too and having the exact same problem as you do. im probably that other person you saw on the website with a sea ray. im changing my tstats this week but ive also been wanting to check the poppet valve because ive seen a couple of people suggesting that. well my problem is that i havent the slightest clue were that is or how to get to it. would appreciate any info on that as well and pictures or diagrams from any site would be really appreciated. its my first outboard so please excuse my ignorance. thanks

 

[andy6374]

Re: 1989 135 hp mercury overheating at mid range

The poppet valve is part of the pressure relief system. All of the components are located on the starboard side of the motor right below the ignition plate. The pressure relief valve cover plate will be attached by 4 bolts, take em' out and replace everything.

 

[imported_tunaman]

Re: 1989 135 hp mercury overheating at mid range

hey andy thanks a lot! finally i can look it up

 

[delsol]

Re: 1989 135 hp mercury overheating at mid range

well i was pissing water good, and steady beeping was found replaced thermostat, popet valve . water pump. but i week late because the day it sounded off i ran it to long and fixed the water flow. but the heat damage was to late..80 hp merc creampuff lake motor clean as new destroyed 2 piston's i am sick over it because the motor was in great shape and i took it for granted
bob

 

[jze1212]

Re: 1989 135 hp mercury overheating at mid range

I have a 1988 100hp that I am having similar problems, it does not do it all the time, sort of strange, it wil start out just is little random beeps then out of nowhere I get the full beeeeeeeeep. I replaced the Tstat about a month ago but the poppet was not in stock and the one in there looked like new so I left it.. New water pump impeller, telltale stream.... So I am gathering that it could be a poppet valve needing replacement? I uses this in salt water and it stays at a slip, can I remove the thermostat and run without?

 

[andy6374]

Re: 1989 135 hp mercury overheating at mid range

Keep the tstat in there. Just replace it, along with the waterpump, every other season

 

[jze1212]

Re: 1989 135 hp mercury overheating at mid range

It is just odd because I just did the thermostat. The poppet valve and diaphram looked brand new, Could it be a bad sensor, I dont have a temp gauge. Once when it went off I removed the cover and the side of the motor was pretty hot, couldnt keep my hand on it for more than a few seconds, is this normal? My smaller Merc never seemed to get that hot, but it doesnt have a T-stat.. Any more suggestions?