hot running merc 135 outboard

[boat4243]

I have a 1985 Mercury 135hp black max V6 outboard motor. while running, the temperature increases directly proportional to the increase in rpm.<br />At around 2500 to 3000rpm it's at the 1/2 way mark on the temp gauge. at 4000-5000 rpm it's at 3/4 or a hair over. at idle its just under the 1/4 mark.<br />There is a strong stream of water out the pee hole at idle and also at high rpm. At high rpm, there is also water pushing out the exhaust (which has been normal for this motor).<br />I have been through all the "posts" on this site and have done most checks;<br />compression in all cylinders 125 psi, within a pound or 2. Checked the poppet valve, appears ok. the water pump was replaced 2 years ago,and the motor hasn't been run much. I looked at the impeller and it looks good. I put the thermostats in appx.180 deg water and they open.<br />I ran the motor on the hose & muffs

• with the stats out and water shoots out of the housing on both cylinder banks. I've also flushed the motor with a hose through the pick up tube with the poppet out and the stats out to purge any material that might be in the system. The motor has only been run in fresh water. Sould I replace the t-stats just in case? I am at a loss for what more to check. I have not had the overtemp warning buzzer go off, but the motor operates too hot for my liking. In the past it has always run no more than 1/4 notch on the temp gauge even at WOT.

 

[Solittle]

Re: hot running merc 135 outboard

Go ahead & do the tstats. I'd also do the impeller. They should be replaced every 2 years whether the motor has had much use or not. Cheap insurance if nothing else.

 

[profish00]

Re: hot running merc 135 outboard

1993 Black max here... IIIII think they just run hot. I replaced stats ,pum, flushed and runs hotter than i like but I think I just need to get used to it...its hot but not scalding.... ahd the heads same way..... hot but not enought to make you flinch....I think they just run hot ...any wan wannna touch this?

 

[AndyL]

Re: hot running merc 135 outboard

I am with Profish on this one as I have owned one of these motors for 10 years. You could check the senders as maybe the one to the guage is over reading. I belive the one on the right as you look forward at from astern goes to the temp guage while the one on the right goes via the module to the alarm system. Someone with better tech knowledge may be able to say if you can swap them over to test.Generally mine will run cooler the faster it goes but temperature has always been my concern too.<br />Andy

 

[CU2NITE]

Re: hot running merc 135 outboard

I have an 85 merc 150 xr2, and I have a simular problem, it runs 1/2 to 1/4 at idle but full throttle it shoots up to a little over 3/4 or 195F. I've changed about everything, stats, pump and houseing, head gasket, checked poppet. I don't know! I've just been running it at 1/2 throttle, about 30mph and the temp seems to be ok. I think the very warm water temps and the nature of this motor may be the problem. I don't think the motor ran this hot early this spring when the water wasn't as warm. If you figure something else out let us know. Good luck.<br />CU

 

[CU2NITE]

Re: hot running merc 135 outboard

I have an 85 merc 150 xr2, and I have a simular problem, it runs 1/2 to 1/4 at idle but full throttle it shoots up to a little over 3/4 or 195F. I've changed about everything, stats, pump and houseing, head gasket, checked poppet. I don't know! I've just been running it at 1/2 throttle, about 30mph and the temp seems to be ok. I think the very warm water temps and the nature of this motor may be the problem. I don't think the motor ran this hot early this spring when the water wasn't as warm. If you figure something else out let us know. Good luck.<br />CU

 

[sag2]

Re: hot running merc 135 outboard

I have had many overheating problems with my 1988 135. You can do a search by my member number to get the whole story. Mine runs hot enough to turn on the horn if you run kneeboard speed for a while. If you speed up or slow down, it cools off. I have checked mine with a ray-tech hand held infra red temp gauge, and it does run up close to 190 degrees when it is running hot. If I were you I would verify that it is running hot. If the alarm does not come on, then it isn't too warm. Also if you are running in fresh water only, it can get warm with no problems. They try and keep them cool for running in salt water. The heat and salt speed up the corrosion.

 

[boat4243]

Re: hot running merc 135 outboard

Thanks for the replys, sounds like others have the same issues with this type of motor. I guess I will replace the impeller and t-stats to be on the safe side and go from there. Just a thought but has anyone had a problem with the pick-up tube/pump housing transition? it does not look like a replaceable grommet.

 

[profish00]

Re: hot running merc 135 outboard

I just bought this 150 merc on a Robalo 18 foot and the temp is always on my mind I replaced the pump impeller and stats, still feels kinda hot, but Im not sure of the temp. I want to put a temp guage in so I can see the temp I used a thermometer and it read around 170-190 at the P hole and thats not enough to put it in alarm but 170 feels warm......DRIVE IT LIKE YOU STOLE IT>>>