1977 Searay GM 250 Inline 6 overheating, no water in hoses, intake not clogged

Gerbot

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Joined
Jun 3, 2012
Messages
4
Hi all,

I have a 1977 Searay with a 250 GM Inline 6 motor. I de-winterized it and it started right up and I put it in the water at the dock. Was monitoring the gauges and temperature gauge just began climbing. I shut it down and checked the outboard and could not find any seaweed or anything clogging the Alpha 1 outboard. Checking the hoses and freeze plugs, no water inside, and did not appear to have been cycling water at all. Opened up hose enough to introduce water into the engine to help cool it and then put it on trailer and went home. Had no problems at end of the season last year while winterizing (with muffs in the driveway). Havent gotten into the engine yet, but any ideas of where to start? Impeller, Thermostat, Water pump, etc? I doubt the thermostat as there was no water on either side of the T-stat indicating that it was not getting blocked form t-stat failure, but not even getting water to that point. Thanks for any anticipated help!

Trevor
 

cr2k

Captain
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Mar 19, 2009
Messages
3,730
Re: 1977 Searay GM 250 Inline 6 overheating, no water in hoses, intake not clogged

When you de-winterized you had it on muffs right? I would start by looking at the water hose that goes from the drive to the transom.
If it is bad you won't get any water to the inside of the boat. I would also check the impeller. Has it been longer then 2 years since it was replaced? It could have died over the winter.
 

ziggy

Admiral
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Jun 30, 2004
Messages
7,473
Re: 1977 Searay GM 250 Inline 6 overheating, no water in hoses, intake not clogged

any ideas of where to start? Impeller,
generally speaking. that's the place to start. specially if ya haven't serviced it for a while. i think the general feeling here on iboats is that a alpha1 type impeller should be changed at the min., every two years. myself. i change mine yearly. it's always new at beginning of the season. it's a very important part of the cooling system.
a kinked hose like cr2k said is possible too.
as for the tstat. ya can remove it and test it in a pot of water on the stove using a thermometer. assuming ya go a raw water cooled engine. it should be a 143*F tstat. when testing in a pan on the stove. it should start to open at 143 and be full open at + 20*, or 163*F.
i've no idea about testing the circulating pump. i only understand them to probably be the least likely to be causing overheat. many other components to check prior to that.

if ya got a service manual (if not, ya can read up here) . there's usually a trouble shooting guide in them. lots of good ideas there, including even mechanical issues that ya wouldn't even think to be related to cooling... you'd wanna be looking at s/m #2 for a '77. confirm proper manual by sn.
 

Gerbot

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Joined
Jun 3, 2012
Messages
4
Re: 1977 Searay GM 250 Inline 6 overheating, no water in hoses, intake not clogged

Thanks all for you responses! Turned out that it was extremely simple. The intake hose had come off of the nozzle that screws into the inside of the lower unit. I put it back on and it was good to go. The impeller had been done a year ago so I did not think it could be that, but I was at loss. Thanks again,

Trevor.
 
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