no power after certain throttle

[krptss]

hi all got a 70hp chrysler engine after half throttle it seems like gear box is nutrializing with no grinding noises i pulled apart gear box, all gears and selector everything is all good. Can anybody please help me out thanks.

 

[Bondo]

Re: no power after certain throttle

Ayuh,... Have a look at the splines where the lower unit interfaces with the motor's crankshaft...
If those splines are in Good shape, I'd guess the hub of the prop is Shot...

 

[steelespike]

Re: no power after certain throttle

I think you may have a spun hub.Pull the prop and draw a indelible line across the hub
make a run and check if the mark is no longer lined up.

 

[krptss]

Re: no power after certain throttle

i checked prop and its not spinning also gears and splines ar all in good shape to not sure wat it can be im stunned

 

[Frank Acampora]

Re: no power after certain throttle

I did get your private message but really, a question like this should be answered on the forum.

There are only two reasons why the engine would appear to "be neutralizing" without any gearbox noises.

1. SPUN prop hub. I know you said it is not spinning on the hub but Recheck it. In most cases, it can not be checked by trying to turn the prop by hand. IT MUST be checked with the engine running in gear and the inner and outer prop hub marked.

2. At about mid throttle, the low speed fuel delivery circuit in the carbs stops supplying enough fuel to the engine and the high speed jet and venturi now supplies almost all of the engine's needs. If the prop is indeed not "spun" then the carbs need to be removed, cleaned, and re-synchronized with the timing. If this is the case, go back to the FAQs in the Chrysler/Force forum where you will find instructions for synchronizing.

 

[krptss]

Re: no power after certain throttle

prop is fine not spun iv had it in the water how would it be the carbies im interested in how it will nutrulise

 

[Bob_VT]

Re: no power after certain throttle

Since this is not a prop question I will move it to the repair area

 

[Frank Acampora]

Re: no power after certain throttle

Well, if the carbs are the problem, the engine will go "flat" after a certain RPM and the boat will lose speed as if it were in neutral. If the engine starts to race like it is in neutral then you need to check the shift linkage. Since forward gear is down, lengthen the shift rod a little and see if that solves the problem. Almost always though, when an engine skips out of gear it is very noisy--that's why your statement that there is no noise confuses me. Search out previous posts on adjusting shift linkage.

Check the shift cable to be sure that it does not have too much slack or play when in gear. Check to see that the correct quick-connects are on the cable ends. Shift cable gets the small one.