1979 evinrude 70hp won’t accelerate past 8mph

[Dallas214Stars]

So I can’t get my motor to go to WOT or even close when I’m all the way down I’m only going about 10 mph if that. Just put a new starter and solenoid as well as a fuel pump. The water pump was recently replaced and carbs were cleaned less than 50 miles ago. New gear oil in lower unit. Did a compression test and it reads 120 in top and middle cylinders and 90 in bottom. I know that’s more than 10% difference but everywhere I’ve read says it will have idle issues not so much power and I should be going more than 10mph at WOT. I have to keep the idle lever up about half way initially to fire it up and sometimes at idle it will die out. I did compress oil through the shifter and throttle cables as they were rusted and it seems to move easily but I’m wondering if they are bad and causing this issue? When I pull the idle lever up it will rev great and even reverse has good power. But forward acceleration is bad. Trying to troubleshoot what’s causing this? Will the bad compression in the bottom cylinder off by 30psi really make it only go 10 miles an hour? Any help is appreciated I wanna get this puppy hauling butt like I know it will!!

 

[oldboat1]

Take off the throttle remote control cable, and operate at the motor. See if there is a difference (2-person job, and still a little dicey). Don't rev on muffs or in a barrel.

I would replace both of those cables as a safety issue if you use the boat.

You might try another compression tester -- don't think you are going to have much success if those are accurate readings (hold off spending money for things like cables until you handle the compression issue or decide not to fix.)

 

[racerone]

Take the cylinder head off.-----It is either a blown head gasket ( cheap ) or much worse.-----No need to spend any coins at this time on other " fixes " here !!

 

[boobie]

What happened ????