1975 Evinrude 70 HP Poor Power and Acceleration-Which Direction Do I Go?

[cheaperts]

1975 70 HP Evinrude on a 20 Ft Poontoon, I just got this motor and isntalledit on the boat last week, finished hook up of cables and such today. Motor will start and idle fairly well. Before hanging the motor I replaced the water pump, and put new plugs in it. Today I backed it in on the trailer, adjusted it in water to get a steady idle, then put it in my slip and ran 3/4 of a gallon of fuel/oil and sea foam through it at idle. We then put 12 gallons of fresh fuel and oil in the tank and set out for sea trials. I don't have a tach, but we are getting about 50% throttle, say 3000 by my ear. While running I checked the throttles to ensure they are full open, they are. I checked the advance and it is against the stop full. We ran a total of 30-40 minutes then put it back on the trailer. The boat sat for 10 minutes while we retrieved the trailer, and did not want to start after the 10 minutes. I tried full throttle, nothing, then I choked it and it fired up, so what does choke for a warmed up motor mean? I pulled the plugs on dry land and broke out the compression tester, 70,70,70....I don't think these results are valid, runs too good to be that worn out. The top 2 plugs look pretty good, the bottom looks to me like it is not firing, I've included pictures of the plugs. Assuming the compression figures are bogus Im going to check spark for each cylinder and am debating pulling the carbs and going through them. Am I wasting my time or looking the wrong direction? All replys appreciated

 

[racerone]

I would expect to see 140 on my compression tester.-----See if spark will jump a gap of 3/8" or more on it.----Sparkplugs are not used doing this test!!----Carburetors must be clean or you risk damage to the motor.----Check fuel pump diaphragm too.

 

[cheaperts]

I have a fuel pump kit so doing that tomorrow, I really think my comp tester is way off or Im doing something wrong, I doubt it would even run at 70 psi.

 

[cheaperts]

Checked spark, good on all 3 cylinders, I'm thinking it must be fuel related

 

[cheaperts]

No Title

Ok, more investigating this morning, started it up on the hose to get her warmed up, pulling #1 plug wire caused a significant drop, pulling #2 killed the engine, and pulling #3 had a very minor effect. Then I noticed that the #1 plug wire was arching to the block intermittently, I moved it with pliers and the engine picked up and smoothed out. OK 1st problem found, time for new coils cause all of them are very weathered.

This still does not explain #3 not running, so I decided to go ahead and pull the carbs and fuel pump and rebuild all of them this week. Once I got the carbs off I studied the reeds with my cell phone camera......And found a SCREW in the #3 reed bank! I was able the extract it with needle nose, but then could see the leafs were damaged. So I pulled the intake, add new reeds to the list this week.

Please correct me if I'm wrong, but this has to be the big issue and why I was showing such weird compression values since the crankcase was not able to seal, I can't help but think by the time I have refreshed carbs, new reeds and good coils we should be in great shape.

 

[racerone]

But the reed valves have nothing to do with compression in the cylinder !!!!---Check where that screw came from too.

 

[cheaperts]

The screw matched the screws that hold the back of the air box to the carbs it ony had 3 screws in it, I'm guessing one backed out or the goober before me dropped one. As for the compression, I thought the case seal/valve health had some impact on compression in a 2 stroke, but if not, the biggest suspect is my cheap gauge, I just don't think it is calibrated or it is leaking. Those look to be an after market or power valve reed, Im trying to figure out now what to order suggestions are welcome.

 

[racerone]

The reed valves are not involved in compression in the cylinder.----Your motor has 3 seperate crankcases.-Air should not leak from one to the other either.----This is based on 40 years experience and not 40 minutes !

 

[cheaperts]

and that's great, it's why I ask here. My question now is do I need to order reeds similar to what is there, looks like the boysen style 2 piece leaves rather than the oem single plate, is it okay to use the factory style on one cyl and the boysen style on the others?