jdaghir
Seaman Apprentice
- Joined
- Apr 1, 2010
- Messages
- 45
I may have mortally wounded my 1975 70 HP Evinrude during decarb and I could use your experience and advice on how to proceed.
Here's the back story:
1975 70 hp, long shaft (20"), mechanical shift, model 70573E on a 24' pontoon boat, turning a 13.25x13 3-blad prop at 5000 RPM WOT. In the last three years I have rebuilt the carbs & fuel pump, rebuilt the water pump, replaced a weak stator & ignition coil and replaced the reeds with Chis Carson Sport fiberglass reeds. Last season the motor was running beautifully - just barely hit the key and it fired right up and ran smooth and powerful.
I've only had the boat out a couple of times so far this season, but I noticed that it was a little harder to start than last year. Knowing that I hadn't done a decarb last season or replaced the spark plugs, I figured it was no big deal. So Saturday morning, I decided to decarb and change the plugs. I pulled the plugs, squirted some Sea Foam Deep Creep into the cylinders and let it set for a few hours. I then cranked the motor a few times to blow out any liquid Sea Foam and put the old plugs back in. I pulled the boat to the water, poured a full can of Sea Foam into a gallon jug and filled it the rest of the way with 50:1 premix. I stuck my fuel hose into the gallon jug and started the motor. I let it warm up a few minutes at idle, and the slowly sprayed small amounts of the deep creep into the carb throats while it was idling. It died once when I put too much in too quickly, but immediately started back up again. After another 5 minutes or so, I launched the boat and proceeded to run at WOT in order to consume the rest of the fuel/seafoam in the gallon jug. It sputtered and hesitated a few times, but I figured that was just from running from a gallon jug instead of a tank. But when we got to about 1/2 gallon left (after 5 or 6 minutes at WOT) the motor suddenly lost power, slowed down and then died.
I tried to restart it, but the starter was having a difficult time cranking the motor. I feared the worse - that I didn't have sufficient oil in the Sea Foam mix and had siezed the motor. I pulled the cowl off and sure enough it was almost impossible to turn the flywheel by hand. But the motor wasn't hot at all - only moderately warm. So we limped back to the dock using an electric trolling motor.
At the dock I removed the spark plugs and let it completely cool. I could then turn the flywheel by hand, but it was still very difficult and sometimes acted like it was sticking - had to wiggle it back and forth sometimes to get it to turn. I called it a day and sadly drug the boat back home.
Today I drained the lower unit and removed it. The lower unit oil was a chocolate milkshake - not good. But to my delight the flywheel now turned easily without the plugs in, while it was almost impossible to turn the drive shaft on the lower unit. I could see a portion of the o-ring on the bottom of the water pump housing sticking out, and when I removed the pump housing, more of the o-ring was caught up in the impellor blades. With the pump housing removed it was now easy to turn the drive shaft. At that point I figured I got lucky and all I would need to do is rebuild the water pump.
But just to be on the safe side, I checked the compression on the motor. The top and bottom cylinder were fine at 125 & 135 psi, but the middle cylinder had none. Zero, absolutely nothing. Looking in the spark plug holes I couldn't see any obvious damage, nor were there any metal shavings on the spark plugs.
I think my next step should be to pull the carbs and intake and check the reed valves. Maybe I'm still lucky and the fiberglass reed valve for the middle cylinder has failed. But if that is not the case, then I think I need to remove the cylinder head to look for catastrophic damaged to the cylinder, rings and/or bore. It this the correct diagnostic path, or is there something else I should be checking?
Sorry for the long post, but I like to provide as much detail as possible. Does anyone have any thoughts, advice or good vibes they could share?
Thanks!
Here's the back story:
1975 70 hp, long shaft (20"), mechanical shift, model 70573E on a 24' pontoon boat, turning a 13.25x13 3-blad prop at 5000 RPM WOT. In the last three years I have rebuilt the carbs & fuel pump, rebuilt the water pump, replaced a weak stator & ignition coil and replaced the reeds with Chis Carson Sport fiberglass reeds. Last season the motor was running beautifully - just barely hit the key and it fired right up and ran smooth and powerful.
I've only had the boat out a couple of times so far this season, but I noticed that it was a little harder to start than last year. Knowing that I hadn't done a decarb last season or replaced the spark plugs, I figured it was no big deal. So Saturday morning, I decided to decarb and change the plugs. I pulled the plugs, squirted some Sea Foam Deep Creep into the cylinders and let it set for a few hours. I then cranked the motor a few times to blow out any liquid Sea Foam and put the old plugs back in. I pulled the boat to the water, poured a full can of Sea Foam into a gallon jug and filled it the rest of the way with 50:1 premix. I stuck my fuel hose into the gallon jug and started the motor. I let it warm up a few minutes at idle, and the slowly sprayed small amounts of the deep creep into the carb throats while it was idling. It died once when I put too much in too quickly, but immediately started back up again. After another 5 minutes or so, I launched the boat and proceeded to run at WOT in order to consume the rest of the fuel/seafoam in the gallon jug. It sputtered and hesitated a few times, but I figured that was just from running from a gallon jug instead of a tank. But when we got to about 1/2 gallon left (after 5 or 6 minutes at WOT) the motor suddenly lost power, slowed down and then died.
I tried to restart it, but the starter was having a difficult time cranking the motor. I feared the worse - that I didn't have sufficient oil in the Sea Foam mix and had siezed the motor. I pulled the cowl off and sure enough it was almost impossible to turn the flywheel by hand. But the motor wasn't hot at all - only moderately warm. So we limped back to the dock using an electric trolling motor.
At the dock I removed the spark plugs and let it completely cool. I could then turn the flywheel by hand, but it was still very difficult and sometimes acted like it was sticking - had to wiggle it back and forth sometimes to get it to turn. I called it a day and sadly drug the boat back home.
Today I drained the lower unit and removed it. The lower unit oil was a chocolate milkshake - not good. But to my delight the flywheel now turned easily without the plugs in, while it was almost impossible to turn the drive shaft on the lower unit. I could see a portion of the o-ring on the bottom of the water pump housing sticking out, and when I removed the pump housing, more of the o-ring was caught up in the impellor blades. With the pump housing removed it was now easy to turn the drive shaft. At that point I figured I got lucky and all I would need to do is rebuild the water pump.
But just to be on the safe side, I checked the compression on the motor. The top and bottom cylinder were fine at 125 & 135 psi, but the middle cylinder had none. Zero, absolutely nothing. Looking in the spark plug holes I couldn't see any obvious damage, nor were there any metal shavings on the spark plugs.
I think my next step should be to pull the carbs and intake and check the reed valves. Maybe I'm still lucky and the fiberglass reed valve for the middle cylinder has failed. But if that is not the case, then I think I need to remove the cylinder head to look for catastrophic damaged to the cylinder, rings and/or bore. It this the correct diagnostic path, or is there something else I should be checking?
Sorry for the long post, but I like to provide as much detail as possible. Does anyone have any thoughts, advice or good vibes they could share?
Thanks!
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