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78 OMC 235

seenredd

New member
"hi, i've got a 1978 seara

"hi, i've got a 1978 searay with an omc ford engine and ourdrive with 2 problems.

1. overheating. i've replaced the waterpump and thermostat. all hoses and cleaned the thermostat housing. with a hose hooked up to it i still goes past 230 degrees and sounds like its boiling water with i turn the engine off.

2. the outdrive will only go down for some reason. this only stared happening after i took it out for the first time and overheated on a lake, barely making it back to dock. i've swapped the solenoids and the only way to get it to go up and down is to connect the up solenoid wire to the down terminal on the other solenoid. i'm at a complete loss here.

i have no idea why it's overheating and electrical problems are always difficult.
if anyone has any ideas i'll take all comers.

thanks"
 
"This probably relates to the

"This probably relates to the other thread we've got going. The Impeller in the lower end of the outdrive MAY be burned out, therefore, no water pickup for the motor. We're debating in the other thread if use of the hose ONLY has a detrimental effect on the lower case impeller, when the boat is on the trailer. Like mine, it MAY have to be run in a barrel of water in the down position to have sufficient water flow for the motor.

Scott"
 
"Note that the impeller in thi

"Note that the impeller in this drive is in the lower end of the UPPER unit, drive must off in order to change it."
 
"You might try ringing out the

"You might try ringing out the tilt switch first, then the harness from the dash back to the yellow coupler on the rear of the engine. There is a connector under the dash that connects the tilt and the shift wires to the harness, then disconnect the yellow cable connector in the rear and go looking for open wires. The blue/white are the up, and the green/white are down."
 
"One other thing with the tilt

"One other thing with the tilt... I ran across the same problem, and found that the circuit on mine was a closed circuit, and I was actually changing out the wrong selenoid. There are dual switches inside each one of them. Sounds wierd, but when I studied the diagram for one of them it made sense. Try switching out the other selenoid."
 
"You should get enough water o

"You should get enough water off of a hose but that is not always the case. It is best to test this with the boat backed into the water.

I work as a mechanic at our family shop that specializes in older omc products and can give you a couple tips.

It is most likely that you have an issue with your water pump or water impeller. I dont know where you are located but in Michigan we often see these units where the owner stored them in the winter with the drive tilted up and water pooled in the impeller housing and has cracked it. If you have not replaced your impeller check for damage when you do so.

The first thing we do when testing one of these is determine where the problem is, on the drive, or in the engine. The best way to do this is to back the boat in the water and with it running remove the water inlet hose from the thermostat housing. Hold it up in the air and you should get about a 4" stream of water out from the hose at 1500 rpms. If you are not getting this much water flow then you are not getting good flow from the drive.

If the drive is your issue (most likely) start by checking your water pump. These impellers last quite a long time, but if it is showing signs of wear replace it, also check the housing over carefully.

If your impeller is worn replace and retest otherwise if all is fine you could have a couple other problems.

Another possible problem is that the seals on the housing where the driveshaft mates up are worn out. Those seals seperate your exhaust gases from your water flow. If you have a leaky seal there, the exhaust gases will get into the water stream and you will lose your prime. Something that we have started to see there as well is that the seals are intact but the housing itself is worn uneven from years of use. That can be a headache to diagnose. If you suspect this might be a problem, replacing your water inlet with a clear hose will allow you to inspect it for air bubbles when running the boat.

Another area to check are the seals where the water passes from the drive into the transom assembly. They are located on each side of the drive under plates that you have to remove to pull the drive off the back of the boat. These may be damaged or improperly installed causing restricted water flow or water leakage. This will usually present itself at low speed only.

Lastly If it is an engine problem, check all of your petcocks as they leak, visually inspect your hoses, and manifolds or tears or cracks and check your thermostat. It is possible for the water pump to be bad, but this is rare in my opinion.

Sorry for the book
hope the info helps though"
 
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