Loose of Power 1975 Evinrude 70hp

[mav6759]

I have a 1975 70hp Evinrude.. I was on the water and noticed a loss of power off and on. When i first left the dock the motor ran fine. I ran the boat to a new part of the lake got to a no wake zone and slowed down. Once leaving the no wake zone, I went to power up no power. It was still running but it seemed like it was missing like it was wasn't getting fuel. The motor was loping up and down. I stopped to fish for about 45 mins. started the boat to move to another area no problems it ran fine. Got to the no wake zone again slowed down, went to power up again after the no wake zone loss power again.. Any ideas...

Mav6759

 

[oldcatamount]

Re: Loose of Power 1975 Evinrude 70hp

It could be a fuel starvation issue. Has it been awhile since you had the carbs cleaned or re-built? I doubt it's an ignition problem as it runs good then doesn't when you change rpm. Is it cooling OK? Is there a stream of water coming from the pee hole? Could be getting a little hot.

 

[mav6759]

Re: Loose of Power 1975 Evinrude 70hp

I don't no if it is running hot or not.. As for the pee hole I really don't see one. I was told that water is put out through the prop. The carb's were cleaned last summer. How can you tell if the motor is running hot.

 

[rongarrett]

Re: Loose of Power 1975 Evinrude 70hp

I have a 1975 70hp Evinrude.. I was on the water and noticed a loss of power off and on. When i first left the dock the motor ran fine. I ran the boat to a new part of the lake got to a no wake zone and slowed down. Once leaving the no wake zone, I went to power up no power. It was still running but it seemed like it was missing like it was wasn't getting fuel. The motor was loping up and down. I stopped to fish for about 45 mins. started the boat to move to another area no problems it ran fine. Got to the no wake zone again slowed down, went to power up again after the no wake zone loss power again.. Any ideas...

Mav6759

When it's missing have someone go to the motor and pump the fuel bulb. If motor starts running w/no miss, replace bulb.

 

[nastyquedawg]

Re: Loose of Power 1975 Evinrude 70hp

I had a similar problem last summer. The screen on the fuel filter was clogged. Come to find out the debri was coming from the fuel line coming from the tank.

 

[mrcj001]

Re: Loose of Power 1975 Evinrude 70hp

Check your fuel system BUT:

It seems to run fine when first started. When the engine heats up its starts running bad. Then you let it set for 45 min. then it starts and runs fine.

It could be a ignition problem. when the engine heats up, it can effect the ignition componets. Usually the power pack. On that engine its bolted right on the cylinder block and that gets hot. If its the original pack, its probably failing.

 

[joey nathan]

Re: Loose of Power 1975 Evinrude 70hp

Mav,
I have same engine. Sounds like fuel delivery to me. Things to check: screen in the pickup tube inside fuel tank, all rubber hoses under the engine cowl including the larger one from fuel pump to carbs. This is the one that gave me trouble (and the same symptoms you describe) - it can get pinched between the engine block and the carburettor silencer housing. You'll need to remove the cover and silencer housing and verify that hose is good and not getting pinched. Careful examination will reveal a "cutout" in the silencer where the hose is properly routed.
Good luck with it!