Help 93 merc 200 EFI intermittent overheat at idle. and engine flooding hard to start

Have mutiple issues, over heat actually started 2 seasons ago but only after winter and during the first few trips out, which is usually right after ice out but lake ussually not fully iced out, so lake temps usually upper 30's low 40's. the alarm sounds about a minute after the thermostat opens, there is no water coming out of the P hole when alarm goes off. during this warm up and i know the thermostat opens because i see steam/smoke, coming out of P hole
i shut down right away, wait start up again, try again same thing, wait again. start up dont wait jump up on plane and then is see water coming out of P hole. but sometimes there is pause in the stream meaning nothing coming out for a second or two. last year it did this a few times out then was ok meaning no alarm but i noticed the stream out of the hole would be interrupted this interuption of water would happen during idle and on plane,
whats the water pressure? good question. i don't know, that broke too. but last year when it decided to work was getting around 3psi at idle and i think 9-10 on plane cruising like 3,500 rpm and upper teens at full throttle. wter pump was replaced 2001-02 was original and actually didnt need it then, so i don't think the water pump is bad.

other new problem, engine flooding out with fuel on start up, i noticed when i turn the key pump would prime for a second or two then shut off, now it constantly runs with key on. just wondering if there is separate relay for this control or if its built into pump.

I don't run the boat during the summer only april and may a few time per 2 months so outboard over the last 5 years sees little run time. and is stored outdoors all year.
Thanks for anyone help with this

Re: Help 93 merc 200 EFI intermittent overheat at idle. and engine flooding hard to s

First of all your motor uses a very small water pump that I change in my v6's every year.. I have two motors like yours and two Bridgeports all using the same small impeller....You got to be kidding us when you say the pump was replaced 10 years ago...I have seen these pumps gone in a year taking a set from non use...Zero hours and needed to be replaced due to taking a set...First order of business is to change the impeller...I would change the housing as well just because I want to eliminate a housing sucking air due to warpage..they only last so long....Your PSI readings are ok which is hard to believe....Spent the money per above and let us know what happens.. Once that is done we can then move in another direction....

Re: Help 93 merc 200 EFI intermittent overheat at idle. and engine flooding hard to s

Ditto, impeller has taken a 'set' and will not move enough water at idle. Yet manages to move JUST enough once up to RPM.

Lucky you haven't smoked that motor, yet.

Change it, at LEAST every other year.

Also, closely inspect the SS parts to see if a 'ring' has been worn into them from the raise seal 'ring' on booth sides of the impeller @ an 1/8 out from the center/shaft hole. If there is wear on the SS parts a new impeller will not seal and pump rebuild 'kit' should be installed.

Re: Help 93 merc 200 EFI intermittent overheat at idle. and engine flooding hard to s

Ok Finnaly got around to droping the lower unit, attached are photos of what i found,
water pump housing toasted, melted, I wonder how that happened. so bad it scored the drive shaft and i couldnt remove the impellar, also the splines on the end of the shaft are tweeked, and im guessing thats not how it was when new.

any recomendation on good site for parts, i tried a couple but when put in my Serial number i get not Found.

Re: Help 93 merc 200 EFI intermittent overheat at idle. and engine flooding hard to s

Best parts site is factory, once you have the factory #'s you can check any other site, or manufacturers cross-reference and be pretty sure that you have the right part.

http://www.mercruiserparts.com/mercruiser_parts.asp

You can get an upper pump kit if the lower isn't warped, or get the complete upper and lower assy.

Yes, that impeller is WELL aged and should have been replaced long ago, the upper looks like it has been run without water for a short time, and it doesn't take too many seconds without any water, but this was done before this impeller was put in or you would see melting of this impeller.

The splines should be coated with SPLINE grease everytime the lower is pulled off to reduce this type of wear. It has shortened the life of this shaft but it willl run for a long time yet, just be SURE to get a tube of spline grease and be sure to use it every time before reassembling.

Re: Help 93 merc 200 EFI intermittent overheat at idle. and engine flooding hard to s

other new problem, engine flooding out with fuel on start up, i noticed when i turn the key pump would prime for a second or two then shut off, now it constantly runs with key on. just wondering if there is separate relay for this control or if its built into pump

Click to expand...

This should not make the engine flood as injectors must be open to flood. Constant pump running is the fuel driver board in ECU...