optsyeagle
Regular Contributor
I thought I might see if the users of this board have come across this issue. I have a 1976 15Hp Evinrude that has an annoying throttle operation. When I open it up to higher speeds I have to hold onto the tiller grip tightly or it will back off quickly on its own and slow the boat down rapidly. I also have a 1975 9.9Hp Evinrude that doesn't do this. It can run on autopilot at any throttle speeds.
When inspecting the differences, I noticed a big difference in their throttle control cams. My 9.9Hp, shown in the 1st picture below has a nice rounded edge that allows the throttle to open and close at a nice consistent rate. The 15 Hp shown in pictures 2 and 3 has a more inverted curve with a nastly little indent at the end. When at WOT, the throttle roller sits on that indent and then it takes a little force to move it off and at that time the roller rapidly moves down the inverted curve of the cam, rapidly slowing down the motor. Also, if I remove my hand anywhere during this inverted curve, the roller immediately moves to the more rounded area, dropping my speed correspondingly.
I am thinking about changing it to the type from my 9.9Hp, but thought I should ask if it will do any harm and also if it should be expected to fit. Has anyone done this?
The throttle cam on the 15Hp is OMC #320819 and the 9.9Hp is #320434. I was told many times that the only difference between the 9.9Hp and 15Hp of this series (1974-1976) was the carburetor, but I have already found another difference right here.
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