Adjusting throttle cam on 57 Evinrude fleetwin

[djboat100]

I'm hoping some of the experts on this forum can help me figure out a problem with my 57 fleetwin 7.5hp.

It seems that the throttle isn't fully opening the carb--the throttle valve isn't going 100% horizontal (it's has about 15 degrees to go). I suspect this is why my motor doesn't want to run as fast as it should.

I've looked at the documentation for adjusting the throttle cam, but there doesn't seem to be a way to adjust how far out full-throttle goes (cam is anchored on the left side).

The only solution I can think of would to be to fashion a longer linkage, but that would probably screw up the timing badly. Everything on my motor looks OEM.

What's the proper way to adjust these? am I correct in assuming that the throttle valve should be perfectly vertical at idle and perfectly horizontal at full throttle? What am I missing?

 

[Chinewalker]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

Yes, the butterfly should be more or less level.

Something quick to check - I had one of these once where someone had doubled up the gaskets behind the carb, effectively moving the carb further from the cam.

 

[Joe Reeves]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

Look very closely at the cam that slides up against the carburetor throttle advance lever.

The metal cam is attached to the magneto armature plate with two screws... 5/16" hex head bolts if I remember correctly. However, whatever the bolts/screws may be... one of the screw holes in the cam is a slot rather than a round hole.

Loosen the screw/bolts slightly and adjust the cam as needed.

 

[djboat100]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

Look very closely at the cam that slides up against the carburetor throttle advance lever.

The metal cam is attached to the magneto armature plate with two screws... 5/16" hex head bolts if I remember correctly. However, whatever the bolts/screws may be... one of the screw holes in the cam is a slot rather than a round hole.

Loosen the screw/bolts slightly and adjust the cam as needed.

That adjustment screw only seems to tweak where slow/start is, but doesn't really have much affect on the left side where full throttle is.

 

[Joe Reeves]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

That adjustment screw only seems to tweak where slow/start is, but doesn't really have much affect on the left side where full throttle is.

Is the armature plate turning the full swing so that the highest point of the cam is against the throttle cam lever? If not, I would assume that the tiller handle gear is out of alignment with the related connecting gear at the vertical throttle shaft..... final tooth of one gear hitting the solid portion of the related gear instead of sliding into its proper slotted location.

 

[djboat100]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

Yes, the butterfly should be more or less level.

Something quick to check - I had one of these once where someone had doubled up the gaskets behind the carb, effectively moving the carb further from the cam.

Thanks, not a dual gasket issue--I recently rebuilt the carb and only used one gasket (throttle issue was present before I did this).

It's off by a large enough amount that I must be missing something obvious, or the previous owner replaced one of the linkages with a shorter one.

 

[djboat100]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

Is the armature plate turning the full swing so that the highest point of the cam is against the throttle cam lever? If not, I would assume that the tiller handle gear is out of alignment with the related connecting gear at the vertical throttle shaft..... final tooth of one gear hitting the solid portion of the related gear instead of sliding into its proper slotted location.

Yep it goes the full distance. I'm beginning to suspect the linkage I have is shorter than it should be. Anybody know how long part #32 in this diagram should be?



http://www.marineengine.com/parts/evinrude-johnson-parts-diagrams/EVINRUDE/ITEM_2831-CARBURETOR.gif

 

[nwcove]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

is part # 32 the same # for a 58 johnson 7.5? if so i will try to get my micrometer in there for a measure.

 

[nwcove]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

ohh wait.....i think i may know what is going on with that motor! part #4 , could not be moving out far enough to allow for full throttle advance....just allowing enough for reverse throttle???

Evinrude Powerhead Parts for 1957 7.5hp 15020 Outboard Motor

 

[kfa4303]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

Are you in Neutral when testing the throttle by any chance? The motor is designed so that you can only open up the throttle about 1/2 way unless you're in FWD/REV gear.

 

[djboat100]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

Are you in Neutral when testing the throttle by any chance? The motor is designed so that you can only open up the throttle about 1/2 way unless you're in FWD/REV gear.

LOL, that's probably it. If so, than this is not the cause of the lack of performance--hopefully the carb rebuild will give it some more pep.

Thanks for all the tips guys! I can't believe how helpful people are here.

 

[djboat100]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

is part # 32 the same # for a 58 johnson 7.5? if so i will try to get my micrometer in there for a measure.

Probably, but don't go through the trouble. The other tip about it having to be in gear is the likely culprit--I don't think the service manual mentions that fact.

 

[Joe Reeves]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

The other tip about it having to be in gear is the likely culprit--I don't think the service manual mentions that fact.

Not if that cam is at its highest setting against the throttle cam lever as you stated in post #7.

 

[nwcove]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

Are you in Neutral when testing the throttle by any chance? The motor is designed so that you can only open up the throttle about 1/2 way unless you're in FWD/REV gear.

not 100% sure about the 7.5, but it should not allow for wot in reverse, and if the stop isnt moving out far enough in fwd, you will only get about 2/3 of wot before it hits the stop.

 

[djboat100]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

Not if that cam is at its highest setting against the throttle cam lever as you stated in post #7.

Yep, being in gear doesnt make any difference. Theres no mechanical connection between what gear its in and the throttle setting at the carb--if throttle is being limited in neutral and reverse, its not by limiting the carb butterfly.

Im back to suspecting that the linkage is too short. If anyone here knows how long it should be please let me know.

 

[Chinewalker]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

There is no reverse or neutral lockout on the 7.5s.

 

[nwcove]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

There is no reverse or neutral lockout on the 7.5s.

i didnt think so either, but marineengine shows that its there? or maybe im seeing it wrong.

best measurement i can get on the rod on my 58 is 38mm.

 

[djboat100]

Re: Adjusting throttle cam on 57 Evinrude fleetwin

i didnt think so either, but marineengine shows that its there? or maybe im seeing it wrong.

best measurement i can get on the rod on my 58 is 38mm.

Marine engine shows four versions of the 57 7.5, the first two of which are wrong (much bigger motor).

Thanks for the measurement, ill check that against mine, but it does sound like its in the ballpark of what i have.

I adjusted the cam out as far as it goes and rebuilt the carb and its running better in the barrel. Hopefully its a big enough improvement to get my 12 foot boat on plane.