2005 Mercruiser 5.0 overheating

[robbrownatc02]

I have a 2005 22' Maxum with a 5.0 Merc. It is docked in salt water and rarely used for a few months. I am using it more now and it is overheating. It seems to always run a little hot, about 175 and at times the alarm goes off. Slow speeds and wakeboarding, starting and stoping it does ok. Sustained speeds at 3000 RPM the temp rises to 200 until I release the throttle and allow it to cool down. There is water circulating in the system and the problem seems to be getting continuosly worse. Where should I start replacing things? Where could there be a blockage from lack of use? Thermostat, elbows?

 

[TurboK9]

Re: 2005 Mercruiser 5.0 overheating

Has the impeller been replaced since it was purchased?

 

[dvan1901]

Re: 2005 Mercruiser 5.0 overheating

Is the drive intake free of any debri such as barnacles and such? Could be the impeller failing, but if it's been sitting in salt and not used, could be gunked up.

 

[robbrownatc02]

Re: 2005 Mercruiser 5.0 overheating

Impeller has not been replaced. Pulled it out and looked, no barnicles on the outdrive. Looks clean of debris.

Is the impeller replacement a diy project?

 

[TurboK9]

Re: 2005 Mercruiser 5.0 overheating

The impeller is cake for a DIY if you can swing a wrench. Especially if you have a manual. Basically just drop the lower unit, remove the old, replace.

It doesn't need to be totally gone to start causing trouble either. A tear, or too much stiffness, can cause problems even if it looks good otherwise. I've always replaced anually in saltwater in the past, and my boat now has a 470 which means I'll be replacing this one annually too. Why risk an overheat and $1000 or more repair over $50 in parts and minimal effort

 

[robbrownatc02]

Re: 2005 Mercruiser 5.0 overheating

Bought the impeller kit and will change it out next week. I hope that works not much boating left. I dont want it to be on the trailer for the rest of the season.

 

[dodgezilla04]

Re: 2005 Mercruiser 5.0 overheating

you didnt mention what outdrive, whether the pump is in the leg or engine driven, it is not hard.

also, is it open or closed cooling? meaning, is there an antifreeze side and a seawater side, or just all seawater?

you can also use a product called salt away when on the trailer and running on muffs to help loosen and disolve salt that has accumulated in the seawater system

 

[robbrownatc02]

Re: 2005 Mercruiser 5.0 overheating

Pump is in the leg and open cooling system. Got the book and it looks pretty easy.

I will also use the salt away while its out.

I noticed that one of the risers was much hotter than the other. Could there be a blockage in there? What would cause one to run hot and one normal temp?

 

[robbrownatc02]

Re: 2005 Mercruiser 5.0 overheating

The impeller was in perfect shape. The thermostat was bad and that fixed the problem. I would suggest replacing thermostat before impeller for overheating problems.

The impeller was easy to replace and a diy project if you have help.

Thanks for your responses.