what is causing the boat to do this after replacing all of these things and it s

[dc_1996]

when we start the boat and run it the temp. gage goes to over 200* then if we take the plugs out of the block and let the water out the temp goes down to normal put the plugs back in the problems starts again we have replaced lower water unit, temp. gage, plugs, sending unit, exhaust elbow unit and flushed the entire system with plugs in and out, it is a 2000 vip 18.5 ft mercruiser 3.0 alpha drive

 

[Don S]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

If the exhaust elbow is staying cold when you see the overheat, I would guess a defective thermostat? If it gets hot, the exhaust manifold may be plugged up?

 

[Mahoney]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

Your best friend is going to be one of those infared temp guns. Make it much easier to follow Dons wisdom and check those things out.

 

[dc_1996]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

we changed the thermostat and he has flushed water with the plugs in and took them out backed the boat in teh water and ran water through with the plugs out water was shooting up everywhere and it was okay for a little bit and we ran it for a while and then we ran it and it went right back up temp. if doesn't feel like it is getting hot to the touch but it may be because we don't run it long enough for it to get hot to the touch

 

[vipzach]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

Where are you touching to see if it is hot? Why did you replace the impellar..............did the old one shread apart and maybe clog something inside the motor/exhaust? Have you tried removing the thermostat (temporarily) and see if the motor heats up then? Also, does it do this on the muffs and when in the water?

 

[dc_1996]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

we took the impellar out because a mechanic at a boat marina told us to replace it and try so we did it doesn't get hot when the thermostat is out but we did put a new one on it
it does do it on muffs and when in the water

 

[vipzach]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

I would try another thermostat. You could gotten the wrong one or a defective one.

 

[lrlima]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

Also, you probably know this but make sure it is a marine thermostat, and not an automotive.

 

[vipzach]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

Also, you probably know this but make sure it is a marine thermostat, and not an automotive.

I am no mechanic, by any means, but I didn't know you needed a marina thermostat! What is the difference?

 

[dc_1996]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

we got the thermostat from a marina so we assume it is the correct one
we put it in a pan boiling on top of the stove with a candy thermometer to verify tempatures and it checked out to match so we assume it is a good thermometer
any other suggestions

 

[vipzach]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

What temp did it open at? What temp does your manuel say to put in? Could it have been put in backwards? Not that I have ever done that!!

 

[dc_1996]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

normally it would run at around 150 but since this problem has arose and it gets hot it is running around 200-225
it is garage kept and covered in the garage and ran fine last summer put it up for the winter got it out ran it one time and half way through the run it started doing it and has been downhill ever since

 

[dc_1996]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

no more ideas on what could be wrong

 

[marunr]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

we took the impellar out because a mechanic at a boat marina told us to replace it and try so we did it doesn't get hot when the thermostat is out but we did put a new one on it
it does do it on muffs and when in the water

If this is the case it would seem to me you have a bad thermostat or it's in backwards as Vipzach said. He was asking what temp the water in the pan was when the thermostat opened. Do you know?

Also, it would seem possible that if this problem started the first time it was used after winter storage you might have some kind of freeze damage. Does it idle smoothly when it's first started? Any steam coming from anywhere? What does the oil look like..any water in it?

 

[dc_1996]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

i don't think it would have freeze damage because it was winterized it also is kept in a heated garage
i don't know if that makes a difference or not also the water when it comes out of the motor when you pull the plugs out seems fairly warm i don't have a actually number temperature wise and it isn't so hot you can't touch it
yes it seems to idle fine even when the temperature goes up i am almost positive it doesn't have any water in the oil
never seen steam coming from anywhere that i know of
when we shut it off after running it for a while, for years it has done this, the motor will cough and sputer until it finally dies, i don't know if that has played a part and finally done something more to the motor

 

[vipzach]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

If the exhaust elbow is staying cold when you see the overheat, I would guess a defective thermostat? If it gets hot, the exhaust manifold may be plugged up?

Did you check what Don suggested? You already said it worked fine without the thermostat in there. If the one you have didn't open until it was 200 degrees, then it is defective, but you don't know without a temp reading. Go spend three dollars on another thermostat and put it in the correct way.

 

[dc_1996]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

called my husband and he states that he has already done as don suggested and as you suggested but he also says that it opens at the correct temperature
he says that he checked those things you suggested

 

[olbuddyjack]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

How about the circulating water pump?
Shaft may have broke or the impellar came loose.
Pretty rare but were running out of ideas.

 

[ndake]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

If it runs cool without the Thermostat then it has to be a Thermostat problem. I have seen more then one thermostat put in upside down. Good Luck

 

[dc_1996]

Re: what is causing the boat to do this after replacing all of these things and

Re: what is causing the boat to do this after replacing all of these things and

i am not sure where the circulating water pump is located on the motor i know that we have two one is at the top and one at the bottom of the motor we have replaced the located at the bottom of the motor but not the top
i know i heard him say on more than one occasion that it doesn't make since that it can be the one located at the top of the motor due to the fact that it is the one that pumps the water through the motor if it wasn't working we wouldn't have water in the motor when we pull the plugs out
is that correct or not