2001 mercury optimax 135 running hot

[Derrick790401]

Help me please I have a 135 optimax that tries to run hot at idle. I have flushed motor out from top to bottom replaced all water lines. New thermostats,new impeller kit, new poppit valve, new water screen in adapter plate and it still does the same thing at idle or long no wake zones. When I get the boat on plain it cools down to 120 degrees with 85 degree water I live in Florida. It’s been to 3 different Mercury dealerships and costing a small fortune it still isn’t fixed. Please help idk what to do.

 

[Sea Rider]

Welcome to Iboats,

Which temp is the motor reading at idle ? What are the issues when at idle, if any ? Have the temp sensors if having them been checked, cleaned, replaced ?

Happy Boating​

 

[Chris1956]

A leaking head gasket can cause overheat. Has that been checked?

 

[Derrick790401]

Welcome to Iboats,

Which temp is the motor reading at idle ? What are the issues when at idle, if any ? Have the temp sensors if having them been checked, cleaned, replaced ?

Happy Boating​

It just continues to climb by the smart craft gauge I usually cut it off by 170 degrees. I haven’t checked the temp sensors yet.

 

[Derrick790401]

A leaking head gasket can cause overheat. Has that been checked?

No sir that hasn’t been checked but thank you I will have it checked.

 

[Derrick790401]

No sir that hasn’t been checked but thank you I will have it checked.

How would I check this, a compression check?

 

[QBhoy]

Check that impeller again, I’d say. Pain in the arse…but all too many times, it ends up being the case. Despite a recent change or check

 

[Derrick790401]

Check that impeller again, I’d say. Pain in the arse…but all too many times, it ends up being the case. Despite a recent change or check

Thank you I will check it out again.

 

[Sea Rider]

It just continues to climb by the smart craft gauge I usually cut it off by 170 degrees. I haven’t checked the temp sensors yet.

Remove both with a proper wrench, those sensors sits screwed into the cylinder's heads, the tip/probe must be clean shinny to provide a correct internal temp monitoring, surely will be found over salted. Can clean/polish them with a Dremel machine and small SS brushes, sanding paper, etc. If found shot, install 2 new ones in.

Happy Boating​

 

[Faztbullet]

What is the flow from water indicator?(peetube) It wont hurt to clean temp sensor but thats not your problem.

 

[Derrick790401]

Remove both with a proper wrench, those sensors sits screwed into the cylinder's heads, the tip/probe must be clean shinny to provide a correct internal temp monitoring, surely will be found over salted. Can clean/polish them with a Dremel machine and small SS brushes, sanding paper, etc. If found shot, install 2 new ones in.

Happy Boating​

Ok I will try that thank you for your help.

 

[Derrick790401]

What is the flow from water indicator?(peetube) It wont hurt to clean temp sensor but thats not your problem.

Good flow from the tell tale.

 

[Derrick790401]

What is safe to do a deep flush on this optimax I’ve heard of people using vinegar,muriatic acid, phosphoric acid to descale water passages in the motor. I cleaned and tested both temperature sensors and both are good. I also did a compression test and all cylinders ranged between 115 and 120 psi. I also removed the lower unit again and checked the water pump impeller and no debris or blockage found. The thermostats are still out of the motor and after all of that the temperature still climbs to the point of where I have to shut it off to keep from over heating at idle.

 

[dingbat]

Quick Google search shows this to be a common problem.

What is your water pressure at idle?

Did you change the spring on the poppet valve as well?

Did you replace the entire water pump or just the impeller?

Did you replace the grommet(s) on the bottom of the water tube when you did the work on the water pump?

 

[Faztbullet]

A 2.5L cannot run without t-stats, goes for Opti ,Carb or EFI. If t-stats are removed you must run restricting washer in place of t-stat. Must have a 3/16 opening or it will get hot at idle as water flows to fast thru block. Also check the stainer in adapter plate as this cools compressor

 

[Derrick790401]

Quick Google search shows this to be a common problem.

What is your water pressure at idle?

Did you change the spring on the poppet valve as well?

Did you replace the entire water pump or just the impeller?

Did you replace the grommet(s) on the bottom of the water tube when you did the work on the water pump?

.5 psi at idle. It’sa complete new impeller kit upper and lower. Yes New grommets as well. And yes complete new poppet valve as well.

 

[Derrick790401]

A 2.5L cannot run without t-stats, goes for Opti ,Carb or EFI. If t-stats are removed you must run restricting washer in place of t-stat. Must have a 3/16 opening or it will get hot at idle as water flows to fast thru block. Also check the stainer in adapter plate as this cools compressor

Yes sir I have the restraining washers in I’m not running the engine anything past a idle right now just trying to get this cooling issue fixed. Strainer in adapter plate is new as well. Thank you for your help.

 

[Sea Rider]

Ok I will try that thank you for your help.

You're welcome. As several parts have been replaced including new poppet valve, t-stats proper time to check, clean, replace both temp sensors specially if that 20 year old motor has been running on Florida's salted waters for that long. No one checks, cleans them as a preventive maintenance whatsoever. Anyway and out of curioity, report the probe's condition found ?

Happy Boating​

 

[dingbat]

.5 psi at idle. It’sa complete new impeller kit upper and lower. Yes New grommets as well. And yes complete new poppet valve as well.

Too low... should be upward of 2-3 psi if I remember correctly.

What is the water pressure at higher RPM?

What water pressure do you get running city water (~60 psi) on muffs through the system w/o the engine running?

Remove poppet and plug hole while running the same test as above.

 

[Derrick790401]

Too low... should be upward of 2-3 psi if I remember correctly.

What is the water pressure at higher RPM?

What water pressure do you get running city water (~60 psi) on muffs through the system w/o the engine running?

Remove poppet and plug hole while running the same test as above.

.5 psi city water with muffs. Wot around 8/9 psi. I will try the poppet valve tomorrow. Thanks for your help.