70 hp evinrude loses power, stubborn

[jbsimpson021370]

I have an older 70 hp Evinrude. I rebuilt it from the ground up 3 years ago. It never seemed to have a whole lot of jump but the last 3 times I have taken it out I have to have someone sit on the bow of my 15' Bumblebee to get on plane and it takes FOREVER to get up. Also it will run great for a while on plane then suddenly it's like someone slams on the brakes and it starts sputtering and at full throttle i'm barely going 7 mph (no Tachometer). Any ideas will be greatly appreciated. I've been told it can be anything from thpack to the carb to a bad plug (replaced when this first started and didn't work.

 

[Solittle]

Re: 70 hp evinrude loses power, stubborn

jb - There are many posts on this site like yours. Many folks start listening to advice from friends and start replacing this and that. They end up turning their wallet upside down and stand back in wonderment on why the latest $250.00 part did not solve the problem. <br /><br />To solve the problem you need to troubleshoot to find out what caused the problem. And to do that, unless you are blessed with devine insight or are a marine mechanic, you need a manual for your motor. Start there.

 

[funnyswede]

Re: 70 hp evinrude loses power, stubborn

We (my father-in-law) has the same problem on a 75' evinrude 70hp. It has 3 cyl, if it runs on two it will be weak. if it runs on one it will run only 5 knots. I got the advice to check if the ignition cables (high voltage) are really secured on the spark plugs. When I checked they "popped out" about 1 cm all the time and would not fit alright. Maybe the rubber has become old and hard?

 

[whofan]

Re: 70 hp evinrude loses power, stubborn

Did you try cleaning the carbs? Carbs seem to be a fussy thing on these motors

 

[rickdb1boat]

Re: 70 hp evinrude loses power, stubborn

I agree with funnyswede on this one. Sounds like you are running on 2 cylinders. Check for strong blue spark on all the cylinders. Bet you find a dead or weak one. Also, check the spark plug condition, as they will tell the story if one cylinder is not firing properly. {Carboned up or oily}