Lightwin Problems

[mike-stroz]

I just replaced the water pump on my ’58 Lightwin and got it back on the water and there’s something wrong with it. When I took it out, it wasn’t going as fast as before, and after a few minutes it died and started smoking (I may have spilled a little oil on it, but not sure if that’s where the smoke came from). I checked the pistons and they are fine, it has good compression, and the fuel lines and carb are clean. What should I do? I’m inclined to blame the cooling system, but I’m just not sure.

[jpatti75]

Are you getting a spray of water coming from the relief holes on the leg, which would indicate whether or not water is circulating through the powerhead? I’d drop the leg again and make sure the water tube is properly connected and double check that the impeller key engaged. If it was fine before, my guess is something we wrong during reassembly.

[The Boat House]

• This reply was modified 5 years, 5 months ago by The Boat House.
• This reply was modified 3 years, 1 month ago by The Boat House.

[mike-stroz]

What is the procedure to flush the cooling system? There’s screw on the side that says something like "cooling flush". I’m going to retrace my steps, but I’d like to flush it just to make sure nothing is blocking the water as it flows through.

[fleetwin]

Why is it that you replaced the impeller on your Lightwin? Was it overheating, or were you performing routine maintenance. I’m hoping everyone is correct, something simple like misaligned water tube/grommet, or perhaps the impeller key/pin fell out during installation.
Keep in mind that if you "missed" with the water tube alignment, it is probably bent now, leaving it up too high in the housing to seat in the impeller grommet properly. The water tube may be rubbing on the driveshaft now, you will want to realign/bend the tube so the driveshaft doesn’t rub through the water tube.

[mike-stroz]

I replaced the impeller because the old one was dry and cracking. One of the veins was almost broken off. When I get home tomorrow, I’m going to tear into it to see if anything obvious is broken misaligned.

[Mumbles]

If the impeller was dry and cracked then the water tube grommet on the pump housing probably was to and needs changing. The small copper water tubes on these motors bend easily and must slide into the grommet smoothly. A light sanding on the end of the tube to remove any crud and a light coating of silicone grease or any grease will help to make sure it reassembles properly. If the tube wasn’t fully seated, it may have been pushed up and rubbed on the drive shaft wearing a hole in the side of the tube. Something else to check.

When building a three horse motor, I find it easiest to install the gearcase first. This way the alignment of the water tube can be checked from the top of the midsection with a flashlight. If everything is good, then the powerhead gets screwed on.

Also make sure the water tube is clear! I have a ’57 Lightwin which had cooling issues. After several teardowns I traced the problem to a small stone which had made its way thru the pump and lodged in the bend at the top of the tube. It would let air pass when blowing it out but not enough water to cool the motor.

[Steve A W]

Did You get an OMC impeller or a Sierra after market one?
It’s been said that the aftermarket ones are too thick.

Steve A W

Member of the MOB chapter.
I live in Northwest Indiana

[1946zephyr]

Yea thats what I was going to say too Steve. One other thing about these 3 horse motors too, is never pull the drive shaft out of the lower unit. Its a real pain to get the drive shaft back into the pinion gear. I spent hours messing around and getting one back in line in the pinion gear. I did it though without pulling the prop shaft assembly.
also, use a light coat of sealer on the top and bottom of the wear plate, so exhaust gases don’t prevent water from getting into the water pump. I just faught this issue recently.

[frankr]

Sorry you had so much trouble getting the shaft back in, but it will slide right in if you hold the gearcase in the right position so the pinion gear settles in place by gravity.

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