1977 115 hp Throttle Question

[Charlie5653]

Hello Folks,
I've been working on this motor for a few weeks now. With all the great help here it's almost purring like new. Went to the lake today for some testing regarding a rough idle and that issue has pretty much been resolved it seems.

The issue I had was - after starting engine (purring like a kitten) then shift into forward and slowly slowly give it more fuel there is a "dead spot" where it just falls on its nose (I think it's around 2000 to 2500 rpm) ?

I can push on thru it real fast and the boat jumps right up out of the water and runs great ? It seems like it's at a transition point in the carbs ?

History :
Model - 115ETL77S
new plugs
good spark
carbs rebuilt / needle - seat - welch plugs
new fuel lines
new fuel pump (not oem - was around 20 bucks)
2 new coils ( old were only cracked, tested good)
compression - all 4 cylinders in the 120's
new water pump
all new lower seals
high timing set to 24 degrees on land -- book states 28 degrees wide open in water
link sync good
seafoam cleaning couple times.

I think thats most of it,

Any Thoughts?

Thanks so much, Charlie

 

[Charlie5653]

Was just thinking, I will mark everything regarding link / sync (I'm pretty sure the carbs are sync'ed together good so will not bother them)

I will do a bit of adjusting to the cam and throttle linkage to see if it will get rid of that dead spot ?

Maybe it's advancing the timing a bit too quick or too slow ?

Am I on the right track?

I can always put it back where it is right now.......

 

[F_R]

Was just thinking, I will mark everything regarding link / sync (I'm pretty sure the carbs are sync'ed together good so will not bother them)

I will do a bit of adjusting to the cam and throttle linkage to see if it will get rid of that dead spot ?

Maybe it's advancing the timing a bit too quick or too slow ?

Am I on the right track?

I can always put it back where it is right now.......

You very well might be on the right track. It is very common for the timer base to become sticky, causing late advance. Disconnect the throttle cable (at motor) and use your fingers to move the throttle where the cable was attached (motor not running). Advancing from slow idle position, the timer base should start to advance, with very little movement of the carb butterfly shafts. This should continue until the timer base reaches full advance, then, and only then, should the carbs be kicked open wide. If the carbs open ahead of corresponding spark advance, it will stumble and maybe even stall.

Of course, the same symptoms will occur if the link is out out of adjustment. (Carbs opening too soon at partial throttle).

EDIT: I just realized you are the same Charlie that has been fighting this motor for awhile now.

 

[Charlie5653]

Great advice,, Thanks again!!! I Will post back with results.

 

[Charlie5653]

F-R, I will advance the cam one turn clockwise and test... Then retard the cam 1 turn and test. Big rain here today so prob will wait until weather permits getting on the water.

The Butterflies on these carb's dont even come close to fully opened?
The book says to adjust to fully opened? The cam rolls fine (pretty much to its limit) and my test yesterday took the rpm's to 5300 wide open (purring)

I can only assume at this point, The Butterflies on these engines are not designed to run "wide open" ??

 

[interalian]

Throttle plates should go horizontal at WOT.

 

[Charlie5653]

Not sure what to do there, the cam will not permit that if it's adjusted to barely touch the carb roller at idle. I know that would be standard (wide open full throttle) do you have a bit more info or any suggestions?

 

[Charlie5653]

The controller and cables are all like new, nothing stretched and no slack