2001 mecury 50hp

[polyskidmark]

Gday guys I have a 2001 mercury 50hp 4 stroke. I am currently having dramas with it. While driving along the motor runs fine until it warms up then it will go into limp mode and sound an alarm. Also the water coming out of the tell tale is not the jet stream it used to be (reduced flow)

So far I have check the impellor and its all fine. I opened the exhust cover and there was no blockage in there however there is some kind of build up inside the thermostat housing (looks like calcium)

Does anyone have any ideas what it could be or what to look for?

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[ducky]

I'd say the thermostat isn't opening up when the motor heats up mate. Get a thorough service done on it by someone reputable. Alan at south side marine gets a great wrap.

[Nude up]

If you use your engine in salt water it is probably salt, it only takes a few marks on the water pump impeller vanes for it not to work correctly. Had a similar problem with my 130hp yamaha I replaced the impeller and both thermostats.

[Dr Drift]

if its going into limp mode its probably over heating. Don't know for sure without running it myself but that's what it sounds like from your description. Sometimes u cant see build up and its actually way inside the small galleries. Could be thermostat as well.... Best get it checked out before u destruct the motor! What area do u live?

[frozenpod]

From what I have seen thermostats don't seem to last in salt water environments very long.

I would replace the thermostat and I would also given the weak tell tale replace the impeller not just the rubber but also the housing/plates.

Most modern motors need to run on the muffs for at least 10 minutes to open the thermostat and flush the entire motor.

Given the potential for salt build up in your motor I would also look at running the motor in a tub with salt away or similar products to help remove the salt.

[polyskidmark]

Thanks for the input guys.

Im in Albury so leigh martin is my point of call.

I actually took the thermostat out and ran it and it still went into limp mode with cool water running out.

I will check the impellor again and give it a flush in some salt away/ radiator flush kind of mixture. And i'll let you know how I go

Cheers

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[rixter]

If all else fails , check out this full service manual http://boatinfo.no/lib/mercury/manuals/50-60.html" onclick="window.open(this.href);return false; , Refer to page 78 & 79 of 552 and check out the section covering the ECM, might even be the crank sensor causing the problem. ?

Thoroughly check all the cooling system first though as mentioned by others. The above book has the info to test the water pressure too... etc etc

Cheers , Rick.

[frozenpod]

I am not familiar with the specific of this motors cooling design but a lot of modern motors will not pass water through the head if the thermostat has been removed and they will overheat even when pumping cool water.

[rixter]

I am not familiar with the specific of this motors cooling design but a lot of modern motors will not pass water through the head if the thermostat has been removed and they will overheat even when pumping cool water.

Your right there with the newer modern motors using a ECM these days, as the ECM reads / and relies on certain programmed (expected) water pressures and temperatures in the cooling system being present at different rpm's; to run correct.
If something doesn't match the set rpm to pressure settings (within a +/- % range), the ECM will alarm and the motor go into safe idle mode.
Reason I was mentioning that it may also be the crank sensor , if this plays up it will set off the alarm also, and go into safe idle mode.

Much like the ECM / BEM in modern cars.

Cheers , Rick.

[polyskidmark]

Just pulled the impellor off and it looks fine to me

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