28 HP early 90s with external throttle

[Sweet Freedom]

I have purchased a pontoon with a early 90s 28 HP Johnson with an external throttle hook up on the side of the engine. I have never seen that and the big problem is, I seem to only be getting about 1/2 engine RPMs when going full engaged on the shifter. I don't feel it is moving completely and has much more RPM to get. ( 9.25x9.25 pitch non through hub prop)

I guess my question is do these run at Lower RPM being they are the SPL models? If not what way to I adjust the cable to get higher RPM, right now at 1/2 throttle I am not even making a wake,

 

[flyingscott]

Look inside the carb and make sure the throttle plate is opening to 90 deg. After that a spark and compression test. How big is your toon?

 

[Sweet Freedom]

its only 20ft, and all that was done, it just seems that until I get past about 1/2 way with the shifter it barely is reving up, that's why I was wondering if its not moving far enough, I'm used to seeing the internal ones, but this SPL has an external hook up. Other problem is I have to do any adjustments upside down or in 8ft of water, I was hoping it may just be the adjuster wheel on the side not setting it in place. Unfortunately this also does not have a tack. But wide open it doesn't sound as wound up as my 40 or my 9.5 Johnsons

 

[flyingscott]

So you are not going to look at the carb or do a spark or compression test? Nothing special about that motor a 30 hp powerhead with a leftover lower unit and new stickers. You are under powered on that toon. Good luck with your motor.

 

[jimmbo]

Does the throttle on the engine open fully when you have the Go-Go lever at full throttle?

 

[racerone]

The SPL motors are exactly the same as the 25 and 30 HP models.----Just a different lower unit / prop / exhaust housing , and therefor marketed as " special " ( SPL ) models.----Should rev up just like a 30 HP model.