Old Big twin 40 hp Little Water from pee hole

[denislajoie]

Hi there i have an old Johnson 40 hp dont know what year cause the transom plate has been replaced, but its white and the carburator has a glass ball you cac see through, there is also a plug in teh side if you want to connect the electric start, if not there is a crank on top of the engine, anyway, there is not much water coming out of the hole, after a while steam starts coming out, of course i never used it like this but just by running in a barrel, took apart the water pump, its almost new, so thats not it, any suggestions where to look next, sorry for the l;ong post but i had to sdescribe the motor since i dont know the year.

 

[Solittle]

Re: Old Big twin 40 hp Little Water from pee hole

The guys can get the year from the model #. Check for it on what looks like a quarter size freeze plug.<br /><br />Can you be a bit more specific about where this pee hole is? Older Big Twins did not come with what is known as a pisser. If the hole is at the back and upper part of the mid section you will not see a lot of water comming out at idle in a barrel until you get the boat in the water and running up to speed.<br /><br />If this motor is new to you I would replace the water pump and thermostat even if it looks brand new. Looks don't mean a lot with water pumps.

 

[Paul Moir]

Re: Old Big twin 40 hp Little Water from pee hole

Does it have a metal or a fiberglass & metal hood? I don't think any 40hp used sight glass on their carburetors but some used them on the fuel pump.<br /><br />More importantly, does your engine have two copper tubes running to the water pump or one?

 

[denislajoie]

Re: Old Big twin 40 hp Little Water from pee hole

Yes its new to me. The hole is above the water line, just below where the hood closes,the glass sight is on the fuel pump your e right sorry about that, it is a fibre glass hood, yes it has 2 copper tubes to the pump. I didnt know this motor had a thermostat? where is that located.

 

[Paul Moir]

Re: Old Big twin 40 hp Little Water from pee hole

Ok, then at least we know it's a '60-'63 40hp. That's specific enough to diagnose. <br /><br />The thermostat is in the head (the part the spark plugs screw into). It is underneath the plate on the top of the head which is held in with three screws.<br />While you have the thermostat out, start the engine up in a bucket with enough water to submerge the water pump. It ought to really gush out of that hole even at idle. <br />The thermostat is about $10. W/P impeller is about the same.<br />Always goop up the thermostat cover screws with sealant or at least grease and they'll remove easily next time. Same goes for the lower unit bolts. Perhaps it's not such a big deal in fresh water, but I doubt I'll ever know. <br /><br />You might be able to pin down the year exactly by leafing through the catalogs over at www.old-omc.de

 

[denislajoie]

Re: Old Big twin 40 hp Little Water from pee hole

thanks, the motor is not here with me but next time i go i ll check that, now could the thermostat be causing the water not to circulate, and what if water doesnt gush out, sory for being persistent but i want to be able to prepare in advance cause there is no computer where the motor is so i cant ask then if i need to....

 

[tashasdaddy]

Re: Old Big twin 40 hp Little Water from pee hole

if the motor is new to you change the impeller anyway. get a manual atleast a seloc, if you can identify model # order an OMC manual from kencook.com.

 

[Paul Moir]

Re: Old Big twin 40 hp Little Water from pee hole

Tashasdaddy's right on. A service manual will serve you very well. It's the #1 service tool and we can really only fill in the details.<br /><br />The cooling system is very simple. Water is sucked in and pumped up the starboard tube. That circulates around the block, across the thermostat, back down the port tube and into the pump to be circulated into the engine again. Once the water is hot enough, the thermostat opens and dumps hot water down though the large hole on the back of the outboard. The entire thermostat assembly is spring loaded so it'll be pushed down and bypassed as the water pressure climbs. That is to say, at higher rpms water is bled off through the large hole in the back notwitstanding the state of the thermostat.<br /><br />So what can foul this system? Stuck thermostat, impeller that's got a 'set' from sitting around (they're star shaped new). Water pump housing or driveshaft seal wear. Those are the big ones. Other possibilities are:<br />The water tubes are crossed. I don't think that's even possible in the short shaft version. <br />Restriction in the water intake. Take off the long reverse water intake plate just above the anti-ventilation plate above the prop and check in there. Follow down to the forward water intake and up into the water pump.<br />Restriction in the block. Hose clamp a garden hose to the starboard water tube and run water through the engine. It should gush from the thermostat opening.<br />Water tubes cracked, out of place, or leaking badly at the powerhead/midsection seam. This will turn up with the above test. Note that the w/p tubes do have a hole drilled through them part way up to cool the innards of the midsection.