2001 Merc 200 EFI - Overheat alarm

[74mph]

Hi Guys,

In my last 2 outings with my 200EFI I had the overheat alarm go off when cruising at ~30mph or around 3300 rpm. As soon as it went off i backed off the throttle an let it idle and run for a few mins, and shut it off. I would fire it back up and it was good to go. Then I could drive at faster speeds like 5000rpm without having the alarm go off. The alarm never goes off at idle or very slow speed.

This just happened in the last two outings and I'm sure I need to do something to fix it. The tell-tale is running a good stream of water and the pressure appears normal at around 10psi or so.

So is it a clog somewhere? Thermostats? Seems like the pressure is good so Im assuming the pump is fine.

Any suggestions?

[BoxMN]

When did you put a new water pump in last? That is first h ing I would check. If it has been more than a couple years, put one in as it would be good maintenance anyway. Good luck.

[74mph]

I have owned the boat 3 years now and its always been the same pump.

I can do this as normal maintenance.

What else?

[JohnMickish]

I'm going to lean towards a water pump too. You can do it yourself if your handy with tools and get a book. It's not rocket science but it's not a 15 minute project either. It's also a good time to change out the output shaft seals while you have it apart.

[BoxMN]

Also, having an extra set of hands is HUGE! Having a vise to put the skeg into while you work helps too - just wrap it in towels and don't tighten too much. I believe there are 6 total nuts/bolts to take off in oreder to drop the lower unit (but I might be wrong, I always forget one somehwere and start to swear ).

Good luck, its not too hard, but getting it all lined back up can be a challenge. Second time is a lot easier. We have 150efi, and Merc 50hp and the mercs are easier than my 25hp Evinrude...

[74mph]

Thanks guys. Im going to pick up some parts tonight. Ill be working on it saturday morning. I have had the lower unit off before when I had to take it in for a new skeg and prop shaft (boo rocks). Ill be sure to ask for any other seals I might need when Im in getting parts.

[74mph]

Hey Guys!

Thanks for your help on here. Saturday I took the time to replace the water pump and flush the system. The old pump didn't look horrible but it was permanently deformed and there were some sand scratches and material lost at the wing tips.

Got it all completed in about an hour. The hardest part was aligning the shift shaft, drive shaft, water tube, and attaching the speedometer tube all at the same time. Did it by myself!

I had it out on Sunday and all appears to be good Ive got about 18psi now all the time, about 20 at full throttle.

Runs great!