Humperdink
Cadet
- Joined
- Nov 2, 2012
- Messages
- 25
Hello, Ive lurked here for quite a while but have not posted much. Thanks everyone for all the random information I have learned from this site.
I noticed there are several threads about cooling and pumping water on these OMC 6 horse motors. A lot never offer a resolution--either the poster was defeated or never came back to say what the solution was. I thought i would share my experience with my 6.
I bought this motor from a guy off craigs list with the intention of tearing it apart and parting it on ebay, a side hobby of mine. He claimed it wouldnt cool and was probably toasted and was a parts only motor. He had installed a brand new water pump and impeller.
It started and idled fine, but overheated quickly, with no water flow. After checking the compression establishing it would stay in gear, i decided it was worth saving. First thing i noticed, the water intake screen is gone. its probably clogged!
First, you want to see if its pumping water at all--is it getting water to the thermostat. I removed the thermostat housing cover and thermostat and started it--nothing. Don't do this for more than a few seconds as the motor will heat up quickly. If you cant get water to the thermostat it is either clogged or not pumping water. To see if it pumps at all, you can put a drill on the drive shaft and submerge the lower. Water should come out of the water tube. If you get nothing here, inspect the water pump housing, impeller, and impeller key.
If it pumps water, but you have nothing at the thermostat, there is a clog, or the grommet is collapsed. There is a rubber grommet that the water tube goes into that can collapse and stop the water. Remove the powerhead to check it. Dont be scared, these power heads come off easy. In my case it was a clog and not the grommet. I found a roll of dog poo bags on the fridge upstairs and peeled them off one by one until the remaining roll was the right size to seal in the thermostat seat. 60 psi through the poo bag seal shot a piece of hardened mud out the bottom of the motor hard enough to penetrate my skin. Still a victory because now i got water at the thermostat!
Now youve got water coming out the relief on the back of the exhuast housing. If your motor has a tell tale you have water there now as well. Fixed right? for some yes, for this one, it was still over heating.
Lucky for me i have another one of these engines. I took it apart and sprayed air in all the holes in its thermostat housing to see what i should expect. The conclusion was that i had a clog in the head and or block. Air in the "pointed" end of the thermostat housing should yeild air out the exhaust relief (not main exhaust outlet under cavitation plate). Air in thermostat seat or hole next to it yielded air out the aux water inlet. I got the former but not the latter.
Off with the Head!
a series of 3/8 inch bolts and youve got the head off in less than 5 minutes. I found pretty much everything was packed with mud. Compressed air in the top left hole, near the threaded holes for the 3/8 bolts, eventually blew mud out of the holes in the recessed area around the cylinders. I filled a fuel hose with water several times and blasted it through there before i made any real progress. eventually the air flowed much more feely and i moved on. air in the bottom right hole again came out the exhuast relief, again no clog here. A look at the head revealed clogged passages here as well. there are tiny holes that, when the head is installed, are adjacent to the cavity around the cylinders. Compressed air cleaned these out pretty quickly. Air in these should come out the small hole that is in the thermostat seat, near the top. After i was satisfied that all passages were clear i reaseembled.
Finally a motor that cools. I ran my known working one and this one to make sure they ran at a similar temperature. Success! When cooling properly, the thermostat housing and cylinder head will be warm, but not too warm to touch.
edit: in case any one loves these motors as much as i do and wants to know what happened to it: my dad needed a fishing motor, he was running a 4 hp long shaft from his sailboat on his tinny. This was a long shaft too, so i short shafted it, sold the remaining parts, and gave it to him. Now he can plane!
I noticed there are several threads about cooling and pumping water on these OMC 6 horse motors. A lot never offer a resolution--either the poster was defeated or never came back to say what the solution was. I thought i would share my experience with my 6.
I bought this motor from a guy off craigs list with the intention of tearing it apart and parting it on ebay, a side hobby of mine. He claimed it wouldnt cool and was probably toasted and was a parts only motor. He had installed a brand new water pump and impeller.
It started and idled fine, but overheated quickly, with no water flow. After checking the compression establishing it would stay in gear, i decided it was worth saving. First thing i noticed, the water intake screen is gone. its probably clogged!
First, you want to see if its pumping water at all--is it getting water to the thermostat. I removed the thermostat housing cover and thermostat and started it--nothing. Don't do this for more than a few seconds as the motor will heat up quickly. If you cant get water to the thermostat it is either clogged or not pumping water. To see if it pumps at all, you can put a drill on the drive shaft and submerge the lower. Water should come out of the water tube. If you get nothing here, inspect the water pump housing, impeller, and impeller key.
If it pumps water, but you have nothing at the thermostat, there is a clog, or the grommet is collapsed. There is a rubber grommet that the water tube goes into that can collapse and stop the water. Remove the powerhead to check it. Dont be scared, these power heads come off easy. In my case it was a clog and not the grommet. I found a roll of dog poo bags on the fridge upstairs and peeled them off one by one until the remaining roll was the right size to seal in the thermostat seat. 60 psi through the poo bag seal shot a piece of hardened mud out the bottom of the motor hard enough to penetrate my skin. Still a victory because now i got water at the thermostat!
Now youve got water coming out the relief on the back of the exhuast housing. If your motor has a tell tale you have water there now as well. Fixed right? for some yes, for this one, it was still over heating.
Lucky for me i have another one of these engines. I took it apart and sprayed air in all the holes in its thermostat housing to see what i should expect. The conclusion was that i had a clog in the head and or block. Air in the "pointed" end of the thermostat housing should yeild air out the exhaust relief (not main exhaust outlet under cavitation plate). Air in thermostat seat or hole next to it yielded air out the aux water inlet. I got the former but not the latter.
Off with the Head!
a series of 3/8 inch bolts and youve got the head off in less than 5 minutes. I found pretty much everything was packed with mud. Compressed air in the top left hole, near the threaded holes for the 3/8 bolts, eventually blew mud out of the holes in the recessed area around the cylinders. I filled a fuel hose with water several times and blasted it through there before i made any real progress. eventually the air flowed much more feely and i moved on. air in the bottom right hole again came out the exhuast relief, again no clog here. A look at the head revealed clogged passages here as well. there are tiny holes that, when the head is installed, are adjacent to the cavity around the cylinders. Compressed air cleaned these out pretty quickly. Air in these should come out the small hole that is in the thermostat seat, near the top. After i was satisfied that all passages were clear i reaseembled.
Finally a motor that cools. I ran my known working one and this one to make sure they ran at a similar temperature. Success! When cooling properly, the thermostat housing and cylinder head will be warm, but not too warm to touch.
edit: in case any one loves these motors as much as i do and wants to know what happened to it: my dad needed a fishing motor, he was running a 4 hp long shaft from his sailboat on his tinny. This was a long shaft too, so i short shafted it, sold the remaining parts, and gave it to him. Now he can plane!
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