135 Optimax mid RPM overheat

[barryll]

I have a 1999 135 Optimax that overheats in the 1800 to 4000 range. It will run all day puttering below 1800 and again, all day above the 4000 range. As soon as I hit that mid range I can see my water temp and CHT raise till the warning system kicks in. The impeller was changed this year. I have noticed that the water pressure above the 4000 range is aboat 5 psi and 15 psi below 4000. Anyone have this experience?

Thanks in advance,
Barry L

 

[JUSTINTIME]

Re: 135 Optimax mid RPM overheat

pressure relife valve or t-stats

 

[gss036]

Re: 135 Optimax mid RPM overheat

Check your poppet valve. Located on the lower starboad side, looks like a figure 8 w/4 small bolts. It is spring loaded but will not jump out a you.
I think you should also change the impeller since you have 5 psi at 4000 rpm, should be twice that. The reason you have highr pressure below 4000 rpm is because the poppet is not opening. It should open around 2500-3000 rpm.

 

[barryll]

Re: 135 Optimax mid RPM overheat

Update - Lower unit has been dropped and all seals checked (new impeller this spring) t-stats replaced, poppet checked and is fine, flushed (several times, just a little sand), sensors checked and are fine. The boys took the boat out with the IR gun and reported on side is running perfect and the other is running hot. They suspect a cyclinder head gasket leak and are going to do a ??? cyclinder leak down test ??? Does this sound normal to anyone?

 

[JUSTINTIME]

Re: 135 Optimax mid RPM overheat

when they open the heads, it might have corrsion or cracked block

 

[barryll]

Re: 135 Optimax mid RPM overheat

OUCH!!!! Glad you broke it to me so subtle Just kidding, i'ts better to expect the worst and hope its not something major.

And if its a cracked block????????

 

[feather thrower]

Re: 135 Optimax mid RPM overheat

I have the same motor, same year and recently had what sounds like the same problem. After running a mid range RPMS it was running hot. On the first test run my mechanic only ran it hard and had no problems. $100 down the toilet. Next time I went with him and got it to run hot my mixing up the speeds. He said my poppit valve was full of mud and stuff and cleaned it out. The pee stream is stronger now and seems to be running better.

I still have another problem, unrelated I believe. Sometimes, usually at first when taking off and hits about 3000 RPM the motor will cut off or limit itself and wont go any faster. It makes a sound like it's not getting fuel but don't think thats it. Once on plane it runs good the rest of the day. Plugs, primer bulb,filters are new. Use quikleen and recently decarbed, no improvement. Any ideas?

Of course it didn't do it when the mechanic ran it. He had the cowl off to hook up gauges and etc, could that have an effect?

 

[barryll]

Re: 135 Optimax mid RPM overheat

I wish it would have been that simple and from what my pressure gauge was reading I thought that might be it. I'm no machanic and I just had three additional gauges installed (water pressure, water temp, and cylinder head temp) so I'm getting use to monitoring this motor. I called the shop while I was on vacation and he said he was sorry they didn't catch this problem before but I can understand that they test it just like I would run it, putter out of the channel and give it the gas when I hit open water. It will run all day at high speed but I ran into a lot a wind during our vacation and when adjusting the speed for the best ride is when I noticed the problem. I should know more this morning when I call them.

Your unrelated problem sounds like the motor is not up to temp yet and it will limit the revs until it is. At least that what sounds logical to me, but like I said, I'm no machanic and I'll leave it to the pros.