Merc Optimax 225 heating up

[bassinbrian]

I have a 2005 Merc Optimax. It gets hot anytime I idle a long distance or run at a very slow speed. I can't tow another boat etc. Without getting a heat alarm. I am the original owner. Its done this since it was new. I change water pump yearly. I've checked all lines and intakes for blockage. Could it be bad thermostats?

 

[fischnrod]

bassinbrian - 10/19/2018 8:58 PM

I have a 2005 Merc Optimax. It gets hot anytime I idle a long distance or run at a very slow speed. I can't tow another boat etc. Without getting a heat alarm. I am the original owner. Its done this since it was new. I change water pump yearly. I've checked all lines and intakes for blockage. Could it be bad thermostats?

If it hadn't blown in 13 years I wouldn't worry about it


sensor

 

[rusty50576]

My
Merc 50 hp 4 stroke does the same thing, hot water comes out the pee hole when it alarms. Always at idle or barely above idle

 

[jbh3]

What is your water pressure at idle and WOT? If you're just changing the impeller, you may consider using the "kit" with gaskets, etc. Another possibility is a compressor over heat causing the alarm. How strong is your tell tale stream? There is a strainer in there that can become clogged. If it was mine, I'd get it to a shop that can read the codes and diagnose the problem and fix it properly. The Tow Boat guy up here tows boats all the time with a V6 Optimax.

 

[FishingwithRusty]

i recently took a boat to fish n fun and was pleased with how quickly they got it in and out. they can hook it up to the laptop and help sort it out. sounds like thermostats but rather than just swapping parts it would be better to actually find the problem before you do the work.

 

[fischnrod]

bassinbrian - 10/19/2018 8:58 PM

I have a 2005 Merc Optimax. It gets hot anytime I idle a long distance or run at a very slow speed. I can't tow another boat etc. Without getting a heat alarm. I am the original owner. Its done this since it was new. I change water pump yearly. I've checked all lines and intakes for blockage. Could it be bad thermostats?

Why didn't Mercury fix it when it was under warranty ?

 

[Buckhornbass]

If you are idling with motor trimmed down try trimmimg it up to 3/4 trim.