2003 Merc Saltwater series 225 hp overheating

[bergz22]

I have a Merc 225 hp saltwater series engine, and last fall the engine overheated up to 210 degrees and there was barely any water coming out of the telltale. Over the winter I replaced the both thermostats, the poppet valve and the water pump with seals and housing and gaskets. I fired up the engine just today for the first time since reassembling everything and there is still a really weak stream coming out the telltale, almost like a trickle. The engine was up to 140 degrees withing 5-10 minutes. This was being ran on muffs in the driveway with the holes in the nose taped off.

 

[bergz22]

Re: 2003 Merc Saltwater series 225 hp overheating

I have a Merc 225 hp saltwater series engine, and last fall the engine overheated up to 210 degrees and there was barely any water coming out of the telltale. Over the winter I replaced the both thermostats, the poppet valve and the water pump with seals and housing and gaskets. I fired up the engine just today for the first time since reassembling everything and there is still a really weak stream coming out the telltale, almost like a trickle. The engine was up to 140 degrees withing 5-10 minutes. This was being ran on muffs in the driveway with the holes in the nose taped off.

Anyone?

 

[oldman570]

Re: 2003 Merc Saltwater series 225 hp overheating

If the motor is a salt water run motor and has not been fresh water flushed after every use, or has sat in the water at a dock for extended periods, there is a good chance that it has a salt buildup in the water passages and blocking the water flow. The use of Salt Away and other products will be needed to get that dried salt out of the motor. This or blockage by parts of old impellers are the most common causes to problems of this nature. JMO
Oldman570

 

[bergz22]

Re: 2003 Merc Saltwater series 225 hp overheating

If the motor is a salt water run motor and has not been fresh water flushed after every use, or has sat in the water at a dock for extended periods, there is a good chance that it has a salt buildup in the water passages and blocking the water flow. The use of Salt Away and other products will be needed to get that dried salt out of the motor. This or blockage by parts of old impellers are the most common causes to problems of this nature. JMO
Oldman570

The boat is from South Carolina, but I believe it was used on the inland or fresh water rivers. It did also sit on dry dock for two years before we bought it.

 

[oldman570]

Re: 2003 Merc Saltwater series 225 hp overheating

Being that the motor sat for 2 years and the motor is a used one, then the best is to pull the LU and replace the water pump impeller, along with a good flushing of the motor to see if any old impeller parts are plugging the water passages. I made a fitting that I can remove the tell tail hose from the cowling and hook the water hose on it for a good back flush along with putting the water hose on the water pipe to the motor and flush both directions. The use of a cheaper infrared temp gun will give a better idea as to the motor temp when running the motor. Most of the motors stats are 143 degree temp and little water will flow until the stat opens. Some stats have a very small hole in them to release any trapped air in the motor and will make the water flow better from the tell tail. If that hole is not there then it can cause a air pocket block at times. JMO
Oldman570

 

[JustJason]

Re: 2003 Merc Saltwater series 225 hp overheating

Most of the motors stats are 143 degree temp and little water will flow until the stat opens

Correct. But keep in mind most of these engines do run hotter than that. On average they run 160 to 170.... The thermostats help control temperature at lower rpms only. At high rpms/full throttle, it's the poppets that control temp at high rpms. The temperature sensors do not activate until you hit 240.

 

[oldman570]

Re: 2003 Merc Saltwater series 225 hp overheating

^1

Correct. But keep in mind most of these engines do run hotter than that. On average they run 160 to 170.... The thermostats help control temperature at lower rpms only. At high rpms/full throttle, it's the poppets that control temp at high rpms. The temperature sensors do not activate until you hit 240.

Oldman570

 

[bergz22]

Re: 2003 Merc Saltwater series 225 hp overheating

After some digging the tell tale port in the block was mostly clogged. It is pissing good now. Any products or procedures to flush the block out with to get rid of any other crud that is in there?

 

[oldman570]

Re: 2003 Merc Saltwater series 225 hp overheating

A good fresh water flush on a set of muffs after salt water use in a must do. Other wise using the motor in fresh water should be enough to clear most crud from the motor. Unless there is a blockage from parts of a old water impeller everything should be a go. Run it like you own it and things will work out otherwise. JMO
Oldman570