1970 bigtwin 40: possible to reverse water tubes?

[jacktrut]

Just wondering if it's possible to switch the water tubes on the evinrude forty? I just replaced the impeller in a new to me boat and there's no flow out the exhaust hole. motor is getting hot. 180 degs. I had never started the motor before I replaced the impeller so I have no idea if there was a water issue before. I removed the thermostat to take that out of the equation. I noticed there's a back flow preventer below the thermostat.. a ball and spring affair. so that got me thinking that perhaps I had somehow managed to switch the tubes by mistake.. I was pretty certain that as I removed the tubes from the lower end I immediately inserted each into the bottom of the power head. I double checked the key way in the impeller and its went in perfectly.. kinda hard to get the vanes on the impeller all tucked nice and neat under the pump housing. I know for a fact the pump is pumping because there is a water leak on the bottom of the power head where it makes the lower end. Hoping someone could shed some light on this before I decide on next steps.. Cheers..

 

[racerone]

Tube on the left goes to grommet on the left at the pump and up in the exhaust housing.----Water in your test bucket MUST be 6 " above the pump.-----Test with ALL thermostat parts installed.

 

[jacktrut]

Thanks racerone. That is where I have the tube running. Thermostat works also. it was open when hot and closed when cool. on the bench (removed from motor when hot)

 

[F_R]

If you leave the check valve out of the thermostat, the pump will suck exhaust air and not pump as it should.

 

[racerone]

?----Are you running in the lake ?---In a bucket / barrel ?----Or perhaps on muffs somehow.----Pictures ?

 

[jacktrut]

I'm running it in a large rubbermaid garbage can.. 50 gallon? F_R check valve is in place. I'll try and post a short vid..
In watching the vid back I noticed I had removed the exhaust shroud extension for the LS model and it was not totally submerged because of the missing piece.. Could that be an issue?

 

[racerone]

It is a cosmetic piece.------Makes no difference on cooling !

 

[F_R]

The shroud extensions are not necessary parts. If the water pump is well submerged, it ought to work.

 

[jacktrut]

[No message]

 

[jacktrut]

snap shot off the vid of motor in barrel

 

[oldboat1]

Tire to hold things stable is a neat idea. I would raise the trailer hitch a little, and see if I could sink the motor two to three more inches, maybe up to the upper housing.

 

[Joe Reeves]

The check valve in the thermostat area is a bypass valve to allow water under pressure to flow around the cold thermostat.

Installing a impeller.... hold the housing in your left hand, the impeller in your right hand, then spin the impeller into the housing. Now... install that 2 piece assembly onto the driveshaft.

It possible, whether you think the pump is pumping or not... that the driveshaft key fell out of place, or the exit tube from the water pump hit the edge of a grommet, folded it over and effectively created a shut off valve.

Water should shoot out of that rubber exhaust relief outlet like it was coming out of a fireman's hose... and since it isn't, if it were me, I'd be double checking that water pump installation.

The lower units on those older twin water tube 40hp models had a habit of corroding away under the water pump plate. If this is the case, it would be impossible for the pump to function as it would draw an excessive amount of air.

 

[jacktrut]

Thanks all for replies. I managed to fix the issue. I bought a replacement motor!

 

[jacktrut]

Thanks all. I appreciate the help with trying to figure out the issues I was having.. However.. My intentions all along were to replace the forty for a twenty. The lakes where we like to fish have a limit on max horsepower of twenty. This little gem came up and I couldn't resist, so here it is! I will likely post a build of the boat as I will be rebuilding the 1970 star craft sprint into a fishing boat. The boat was headed to the landfill so I managed to get it for a song (free!) so here it all begins.