Still overheated..whats next?

[pbuzz3323]

2003 searay..5.0 MPI, 260 Hp engine...S/N..0m624941 ...Ok heres the problem...I changed the seawater impeller and the thermostat this spring as it overheated on last trip last year. Replaced everything and started right up...ran fine..until the overheat alarm went off...This was with muffs on in driveway...Now I have new Impeller and thermostat and problem remains. Took 1 blue plug out and started it and water flew out so I guess the impeller was fine but it seems like Im getting no water to the top hoses to the thermostat housing. Put blue plug back in and took all hoses off thermo housing , cranked it up and no water from any top hose....where else am I going to look??? when I started it I did have some water coming out the exhaust but The same problem remains as before the changes...Is the impeller the only thing that pushes water or is there another water circulator that could be bad?? Im at a loss here now.....OH...and when I went to shut it the key turned back to off position and boat kept running..Had to hit the switch on the shifter to shut her off. I just dont know whats going on now..the old Impeller was fully intact also so no parts are clogging. Anything please...HELP

 

[erikgreen]

Re: Still overheated..whats next?

What type of thermostat did you put in? I think it's normal for the top two hoses not to have any water coming out until the thermostat opens. It sounds like it's not opening up, so the engine just keeps heating ip.

What temp is the water alarm set at?

I can't say why it didn't stop when you turned off the keyswitch, except maybe a bad keyswitch....

Erik

 

[CharlieB]

Re: Still overheated..whats next?

Pull the water supply line to the motor, crank the motor or fire it briefly to verify good water flow/supply.

Excess water from the raw water pump bypasses the motor, going straight to the exhaust manifolds, a restriction at the stat pressurizes the block with air, restricting the inflow of water. The motor rapidly heats.

Possibly the T-stat is stuck shut, take it out and heat it in a pan of water with a thermometer, note when it begins to open and again when it is fully open.

Drill a 1/8 inch hole in your new stat to bleed air out of the block, many newer style stats already have a bleed hole in them.

 

[CharlieB]

Re: Still overheated..whats next?

Reread original post and clear that you already changed the stat.

If the water pump belt is loose or a problem within that water pump. Test that pump flow by leaving the t-stat out and the housing OPEN, fire the motor, water should rapidly flow out of the stat housing, if not you may have a waterpump problem.

Is that a serpentine belt/reverse rotation pump?

Did you change that pump just before you went out last fall?

 

[pbuzz3323]

Re: Still overheated..whats next?

I changed the impeller and the thermostat..I used the proper parts as I went from the schematic diagram...I just pulled the water circulating pump and it appears ok..Now I gotta find the gaskets..I also took off the cover on back of water circ pump and everything spun what appeared normally. unsure about the reverse rotation though..Maybe I will reinstall without the stat and leave blue plug out and see what happens. I have to do it without new gaskets though for testing purpose. Doesnt look like theres anything inside the water pump to go bad.

 

[Mkos1980]

Re: Still overheated..whats next?

At what temp does the buzzer go off?

 

[pbuzz3323]

Re: Still overheated..whats next?

Actually im not sure what the temp was..The alarm rang and I jumped to shut it..It was maybe around 175 but not sure..I just found a good deal on a pump and ordered it..whats another 80$..God its making me sick!!! But thats the joy of ownership! I just cant figure what else it may be..Its not really a complex system.

 

[Don S]

Re: Still overheated..whats next?

You may have a bad alarm sensor. If it only showed 175?, that is about right.
You say it overheated last year, what did the temp go to, or did you just hear the alarm and assumed it was overheating?????

 

[pbuzz3323]

Re: Still overheated..whats next?

I believe the temp went to around 200 last year when it happened but cant be 100% sure..I know today the alarm rang before it hit the 175 degree mark...Also I just reinstalled everything without the thermostat and the first 2-3 times I got no water to the top...Then the 4th maybe 5th try I reved it alittle and finally got water..but whats weird is..Every 2-3 minutes the alarm would sound with 2 beeps then stop..2-3 min again then 2 beeps ..Now when it was just running it was making a clicking sound .Like a bad bearing and the belt was drifting slowly off the left side pulley above the seawater pump and the seawater pump itself...Just to add..The clicking sound and the drifting belt didnot occur earlier today during the first startup...just this last try

 

[Don S]

Re: Still overheated..whats next?

An overheat sound a single steady beep till it cools down. There are several things that can cause the alarm you are hearing, and it's not overheat.
Your best bet, unless you have a manual and the equipment and abilities to troubleshoot electronic EFI systems, is to take it to a qualified Mercruiser dealer. It sounds to me like a lot of DIFFERENT issues going on at the same time.
Now if you have a way of checking fault codes, a DVM, the OEM service manual for your engine and ECM and want to try and troubleshoot it, we can help.

 

[pbuzz3323]

Re: Still overheated..whats next?

I dont have the equiptment to check these things but If I remember right it was long beeps that were going off last season and earlier today. Also now see that none of my accessories are working , bilge, horn, lights and Im wondering if its from a bad ignition switch. I can turn key to off position and take key out and it still runs...Can that effect all the other accessories if its bad? Loosened the serpentine belt and clicking/tapping stopped. Can You buy this particular key or is it a dealer item?

 

[Don S]

Re: Still overheated..whats next?

While there is a higher than average chance you have a bad ignition switch, that may not be the problem. With the other problems at the same time, it sounds like some serious wiring problems. Other than the actual overheat (of only 200? which will not damage the engine) nothing makes sense.
Did you by any chance install something new on the boat and maybe drive a screw into the wiring harness?
You need to get it looked at by someone with some serious experience.

 

[pbuzz3323]

Re: Still overheated..whats next?

PROBLEM SOLVED!!! Who would have ever thought that 1 damn ground wire to the battery would cause the electrical problems..All Of them. As to the overheating...All is pumping well now need a decent prime and the muffs werent really supplying it. One question I still have is..My smartcraft reads .5 and .6 water pressure at idle..Is that low?