Overheat--

[bnk999]

Yesterday Had the boat out -- Running fine for first hour -- stopped at a park and ate lunch-- Then ran it for about 5 minutes and it died-- when I turned the key back to "on" the buzzer was going off -- waited about thirty minutes for it to coll off -- started it back up and was getting water out of telltale while I was idling so I started heading back to the ramp slowly around 2000 rpm- it died again after about 5 minutes. I let it sit for an hour then tried to start again and it would crank but not start. I'm thinking I might have got sand in the cooling system which may have caused the passages to get blocked?? I didn't think to check the telltales while I was underway, I only checked them at idle and they seemed fine- A few hours and a long tow I got it home and pulled the plugs they all looked fine. What do y'all think-- replace the impeller of course, check compression?

 

[eurolarva]

Re: Overheat--

Please post your model number and horse power. My guess is your impeller is shot on your water pump. There could be blockage there somewhere. Either way you are going to have to remove the lower unit to see what is happening. Even if impeller looks good it could be shot. At low speed such as idle it may be kicking a little bit of water up there and at higher speeds it just isnt tight enough to create water pressure. model number is critical along with make of motor. Before you take that lower unit off you are going to want a spare impeller. You should also get yourself a service manual. It takes the guess work out of what you are doing.

 

[Docdoc]

Re: Overheat--

You might want to check your thermostat to see if it is damaged or clogged. Did you hear the heat alarm (buzzer) any time during that first hour you say it was running ok? See if it will crank up on the muffs now. Did you check to see if you were getting fuel to the carb? You may have a clogged fuel filter. If it got hot and now won't start, my guess is you've got a lack of compression (galled piston, etc.) Replacing the impeller ain't gonna help that. Just for grins, I'd put a compression gauge on it and crank it to see what it looks like.

 

[bnk999]

Re: Overheat--

1974 75 hp chrysler -- yes fuel to carbs-- fuel pump is working fine- filter is clean --

 

[scotiany]

Re: Overheat--

It might be something as simple as water inlet blockage. At any rate, like eurolarva said, it's best to take off LU and check your impeller and water tube. You might want to hook up a short length of garden hose to the water tube and blow on it slightly to sense any blockage.

 

[bnk999]

Re: Overheat--

Thanks for the help guys, I will run a compression test on it this weedkend .............................while I cross my fingers

 

[bnk999]

Re: Overheat--

OK couldn't wait till this weekend -- here are the numbers from the top down 119 - 121 -- 49 -- Pulled the head and sure enough the bottom piston was burned-- cylinder looked fine though- Ok so how hard is it to replace the powerhead if i were to buy a rebuilt one?-- iboats has one for 1150 ~ give or take-- is it worth it to rebuild it myself, or just replace it? or just scrap motor and start anew- everything else on this motor is immaculate-

 

[eurolarva]

Re: Overheat--

Removing and replacing the powerhead is pretty easy. There are about 9 bolts holding the head on. You may need help getting it off because of the weight. My guess is around 100 lbs for the head alone. The shift linkage, throttle linkage, carb and linkages, and the termanal strip will all have to be removed as well. You will need a new upper and probably lower gasket for the kingpin. Those gaskets will be about 35 dollars and some non hardening liquid gasket. <br /><br />I am suprised Iboats has a power head for this motor. Other considerations you may want to consider with a motor of this age is what condition the gears in the lower unit are in. A motor of this age could give you problems with worn gears. If those gears have not been resurfaced it can be done at a machine shop for about 50 dollars. What they do is re square the clutch and forward gear faces so they are like new.

 

[bnk999]

Re: Overheat--

Looks like I will go ahead with replacing that powerhead. Thanks for the nfo euro, Now about this lower unit machining, I guess I would have to diassemble it completly and take the gears in, is that correct?

 

[eurolarva]

Re: Overheat--

Yes but if it is working now dont mess with it. As long as the lower unit oil is clean with no water and the shifting dosent grind or jump out of gear it could last a long time.

 

[bnk999]

Re: Overheat--

Yes it works great -- First time I had it out (it sat for 7 years) It chattered a little going into gear. (with fresh oil) But after changing the oil again it went away- no signs of water or metal...

 

[bnk999]

Re: Overheat--

Bought a powerhead on ebay- Sounds like it'll do the trick- especially for the price -- What do y'all think?<br /><br /><br /> http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=4544581201

 

[eurolarva]

Re: Overheat--

350 bucks is a good deal. Hope everything works on it. good luck

 

[bnk999]

Re: Overheat--

I'm having hard time finding the kingpin gaskets for sale. Is there another name for them? my motor is a 757HA. I looked here, but didn't see em' Would anyone happen to have a pert #?<br /><br /> http://www.mercruiserparts.com/Show...2.1/10.png&inbr=1729&bnbr=50&bdesc=POWER+HEAD

 

[eurolarva]

Re: Overheat--

Here is a link for a complete gasket set for the powerhead. They give the part numbers for each gasket in the kit so maybe you can find one that way. The whole set is about 40 bucks. part number 18-4313 shad connection powerhead gaskets