1975 Evinrude 135 not putting out full power.

[gjmsd]

I have an 1975 Evinrude 135 that does not seem to be putting out full power at WOT. I've had a similar boat (16' low profile speedboat) with a Merc 115 so I have an idea what it should be doing. The engine just doesn't feel like it is running all out. I pulled the cover off and inspected the throttle linkage and I don't think the carb butterflys are opened fully at WOT which I'm guessing is my problem. Picture 1 shows the linkage at idle, picture 2 shows the linkage at WOT and picture 3 shows the linkage at WOT with me rotating the butterfly valve to wide open and away from the cam. I'm assuming I need to adjust the linkage marked "x" so that the butterfly is closed at idle but fully open at WOT.

I have a manual but the diagrams don't quite match up with what I have so if anyone has any input, I'd appreciate it.

 

[emdsapmgr]

Re: 1975 Evinrude 135 not putting out full power.

You can't properly check the position of the carb butterflys without pulling the airbox cover off. You have to visually see the butterflys in the carb throats. They need to be level (horizontal) at WOT. It is possible to incorrectly adjust those carbs butterflys so that they will actually over-rotate (too far) and start to close. You can't tell by looking at the side of the carbs.

 

[gjmsd]

Re: 1975 Evinrude 135 not putting out full power.

Well that would explain why the manual said to pull it off. So it might actually be full power. Thanks, I'll check tonight.

 

[gjmsd]

Re: 1975 Evinrude 135 not putting out full power.

Pulled off the cover and as I expected, the valve is not fully open. Went through the synchronization process and everything lines up. By adjusting the trunnion nut I can get it to full throttle and then it hit me, I adjusted the trunnion last summer to get the engine idle RPM lower thereby causing it to not get full throttle. I played with adjustment a bit and still not happy. It seems I can't get low RPM and full throttle with one adjustment. Maybe my throttle cable is a bit worn and needs to be replaced. I also lubed all the pivot to see if it returns to idle easier. I'll fire the engine up tomorrow and see how it idles.

 

[emdsapmgr]

Re: 1975 Evinrude 135 not putting out full power.

Did you detach the throttle cable at the engine end when you started doing your adjustments? You want to be able to manually move the engine throttle lever and get the full idle to WOT range of movement on the carb butterflys. Once you do-then reconnect the throttle cable.

 

[gjmsd]

Re: 1975 Evinrude 135 not putting out full power.

Yes and it moves easily between shut and fully open. Just can't seem to get the full range with the cable and throttle which is why I'm wondering if the cable is worn and has too much play. Going to play with the adjustment tonight with the engine running to see if it goes to idle at the current setting.