[Augwen]

On a 135hp Optimax...how often should you have to replace the impeller? How long can this motor idle safely?

[ricksrster]

The rule of thumb is replace the impeller every 2 years whether you think it needs it or not. Better to be safe than sorry. As long as there is water going through the pump,it should be able to idle for a very, very long time. You should have an overheat alarm on your motor. Also, you can install a pressure gauge.
I've been thinking about going with a 135 Optimax. Tell me how you like it.

[KCLOST]

You "should" have a water pressure guage installed on that rig.. If you don't (and that is not a slam on you) I would strongly recommend that you do....

Check with Merc, on the water pressures you should have at idle and WOT. That is the best investment you can make on a V6....

Rick is also on the money on replacement.....

[JUSTINTIME]

check it every year, and they say 2-3 years
i do it every year
it is cheap insurance from a power head meltdown

[ozziebob]

Why do you need a pressure guage on a opti???? The ecm will set the unit in to guardien mode if the pressure drops to low!!! How many times do you kneed to be told there is a problem? It aint going to help you much, Just going to cost you extra money!

[Capt Ken]

If you're running the engine in salt water, change the thermostats also with the impeller. The corrosion on those things after two years can also cause problems. With the OptiMax, you will need to pull the fuel rails back a inch or two to get the thermostat cover off, but an easy job.

[andy6374]

I too like a water pressure gauge. Call me old fashion, I don't like to rely on the ecm to tell me that my water pressure is way low (although you end up trusting the ecm for other things).

Along with the impeller and tstats, I recommend replaceing the pressure relief valve components every 2 seasons. Even if you don't replace all the components, it's nice to clean everything out and also to make sure no debris is caught up in the spring.

[Augwen]

Hey Rick, I like the Optimax with the exception of having to change the impeller because the ECM keeps telling me I have a heat problem. Also sometimes the ECM starts beeping after it has been idling for just 30 to 60 minutes. At that point I shut it down, let it sit and everything is fine. Maybe it is a bad connection in the ECM?