I do think changing impellers every year is overkill as well. But with my boat being such a pain in the ass to get to them. I do not want to do this mid trip, or season. And they have been installed for 3 years/ 2 seasons. So I am replacing them, and plan to get a feel for how much of a pain in the ass it is. But we go way more seasons then most on my dad's boat and never have a problem. (Twin 496 in formula). But 2-3 years will be my routine I think for this one.

I do not have mechanical water pressure gauges.

I do have a mercruiser scan tool and car watch the electrical sensor live. But I have yet to do so. I will do this when I am letting the engines warm the oil for the oil changes. (Going to use the old impellers for that so no risk on the hose, then once oil is changes remove pumps and swap impellers.

What is the range I am looking for? Where is the point it's to low and sets off the alarm, to hi as well?

Sure would be easier to install new sensors while housing is in my hand. Or clean the path to the sensors.

As far as pump housings, I thought they where way to much and the stainless 400 buck one was the way to go IF you have to replace? They also make a kit to fix your old housing? Have been told that works as well.

Where are these 100 buck housings? Might do just that if so.

I don't think mine has a factory freshwater flush on it?

You should see 5 pounds of water pressure on the hose at idle. You should see it go up and down/vary a bit. That's assuming you have good water flow out of your hose.

Are you using muffs over the drive? Or do you have garden hose fittings in the engine compartment?
Fresh water flush garden hose fitting looks like this:
[ATTACH=CONFIG]516180[/ATTACH]

If you are using muffs, and you have dual water pickup drives, make sure you tape over the out set of pickups that the muffs are not covering.

I bought my last pump/impeller locally for around $100 bucks. Check your specifics out on www.mercruiserparts.com . You can do anything a parts counter rep. can do with that site.

The sensors are easy to swap/replace. Takes about 5 minutes.

Yes I. Have that page saved. Ha that's where my pics in my other thread came from,

I do not have the fresh water flush. I use muffes, with the low water pick up tapped off. I assumed that in your pic was what you where referring to, but did not know if maybe I have missed something.

So 5psi @ idel. What about with cursing at 3000 rpms? And where is the hi and low limit that sets the alarms off?

Not sure. That's where the book would help. :D Or a mechanic.
Water pressure could be all over the place, it depends on how deep the drives are, speed of the boat, types of pickups, etc. etc.

There is a range which is something like 25-35 lbs. (DO NOT quote me) that is spec for Mercury. My mechanical gauges are pegged at 35, at higher speeds and no issues.

I have the factory merc books for on the motors, but don't remember seeing that spec, will look again to be sure though.
Thanks.

i've been told to sand the Inside of the pump cover smooth, if it's rough...FWIW

Ok bumping this old thread.

I got a new sensor, but then the other motor did the alarm too, and i was replacing impellers anyway. SO:

Did new impellers, and ran boat down the river. No alarms yet. BUT when I scan the motors:

Starboard sensor is reading 4.8 psi at idel (average with fluctuation), and then on plane around 3500 rpms, 37 ish psi.
Port sensor is reading 43.6 psi at idel (and not moving around), and then on plane around 3500 rpms, 40-43 ish psi.

SO while I have the back seat out and can replace the sensor easy... should I replace the port one since it seans stuck? I would if it was the same side that was giving me issues before. but its opposite... and I only have once sensor at this time.. and seat has to go back in for a run.

Double post.

Absolutely replace it. If it's stuck at high pressure, your computer/alarm will never know if you have a water pressure problem.

Your sensors are not the issue, nor are your impellers. I'd be glad to elaborate if you like.


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