Motor stutters at high end speed [video]

[PensacolaJason]

This is my 1983 50hp Johnson. When you push the throttle down to a certain point it starts this stuttering until you dial the throttle back down and then it runs smooth.

I'd say you can give it about 3/4 throttle before this starts to happen. I have no idea what this might be so any help would be appreciated.

 

[willy007]

Re: Motor stutters at high end speed [video]

What are your rpm's at the "3/4 throttle"? Additionally, have you checked to see if your primer ball is good 'n' hard when this happens? Your fuel pump may be struggling to keep up at full throttle... just a thought

 

[Jambone]

Re: Motor stutters at high end speed [video]

Could also be a partially plugged fuel filter or carburetor float setting.

 

[PensacolaJason]

Re: Motor stutters at high end speed [video]

Thanks for the help. I purchased a new prop and a new fuel pump, so I'll install both when they come and report back if that made a difference.

 

[phillnjack2]

Re: Motor stutters at high end speed [video]

i would of looked for dirt or wrong float setting or a float that is sticking up.
and are you getting plenty of water from the tell tale ?


be good to hear what results you find with new pump.





phill

 

[PensacolaJason]

Re: Motor stutters at high end speed [video]

Yep, the motor is pissing a nice steady stream.

 

[phillnjack2]

Re: Motor stutters at high end speed [video]

I watched your vids acouple of times.
that is definitely dirty carbs or fuel lines.
and possibly a set wrong float.
it goes ok till about 3/4 then it just dont get enough fuel. that nmakes it seem like float setting could be wrong.
you might find the float has been put in upside down,ive seen this a lot on outboards.

hope you get sorted as it runs good untill high speed


phill

 

[PensacolaJason]

Re: Motor stutters at high end speed [video]

I watched your vids acouple of times.
that is definitely dirty carbs or fuel lines.
and possibly a set wrong float.
it goes ok till about 3/4 then it just dont get enough fuel. that nmakes it seem like float setting could be wrong.
you might find the float has been put in upside down,ive seen this a lot on outboards.

hope you get sorted as it runs good untill high speed


phill

Thanks for the information. I've always assumed it was a fuel issue, but wanted to rule out some of the simpler fixes first. I'll definitely have a mechanic check out my carbs if the new prop and fuel pump do not correct it.

Someone told me that it could possibly be that the fuel pump is having trouble pushing enough fuel to the motor at high speeds, which is why I decided to change out the pump. Does that sound likely? others have said it could be a spun hub in the prop.

 

[phillnjack2]

Re: Motor stutters at high end speed [video]

its 100% nothing to do with the propeller.
i dont care what they say about spun hubs, if was the hub spiing then you would get higher revs just not go any faster.
this is a fuel issue.
the fuel pump could need a rebuild kit,yes it could be that,but i would sooner go for high speed jet blocked or dirt in the
carb bowl and float setting not right.
cab is a easy thing to do yourself, it realy aint hard one to do at home.
ive got those of and cleaned in not time they ae a easy fix to be honest.
Do get yourself an inline filter as well, thiose cheap throw away ones you can see through the plastic are good enough and very cheap
they can save lots of rubbish getting in the carbs.

also when you store it or put it away after use, do you run it out of juice in the upright position ?
or do you just switch it off ?
if you just turn it off how long is it then left for before used again ? as it can be fuel gummed up in the carbs if left a while.
modern petrol dont like to sit around too long before turning to varnish and gum in a static place.

just a few thoughts on it..

by the way what size prop have you ordered for it ?
and what size was on it when running in the vid ?

phill

 

[PensacolaJason]

Re: Motor stutters at high end speed [video]

I usually just turn the key off when finished running the motor. I typically go fishing every weekend, but often run it at least once during the week on ear muffs.

The current prop on it is a Michigan 12-1/4 with a 15 pitch. I am replacing it with a Solas Amita 12-1/4 with a 15 pitch. To be honest, the prop on there now is in pretty bad shape and needed to be replaced anyhow. It has a few bad chips and the blades look as if they have been shaved down on the edges.

 

[phillnjack2]

Re: Motor stutters at high end speed [video]

once its all corrected it will go very well.
50 hp with a 15 pitch will easy see 33 to 35mph on that boat with light load.
definitely be a huge speed improvment to what your getting now, and run a lot smoother with new prop.

phill

 

[PensacolaJason]

Re: Motor stutters at high end speed [video]

That's what I'm hoping. Right now I get to about 25-28 mph before hitting the motor stuttering issue.

 

[PensacolaJason]

Re: Motor stutters at high end speed [video]

UPDATE: I replaced both the fuel pump and the prop this weekend and the stuttering is completely gone now. The boat runs extremely smooth and has even picked up some extra speed. The only problem is that I don't know which (prop or pump) corrected the issue. Just glad everything is running well now.

 

[willy007]

Re: Motor stutters at high end speed [video]

:clap2: Congrats! Glad to hear that the issue is taken care of! Thanks for the final update also!

 

[TwoRivers]

Re: Motor stutters at high end speed [video]

UPDATE: I replaced both the fuel pump and the prop this weekend and the stuttering is completely gone now. The boat runs extremely smooth and has even picked up some extra speed. The only problem is that I don't know which (prop or pump) corrected the issue. Just glad everything is running well now.

Good job on getting rid of the stuttering.
My guess would be fuel first then prop.
Enjoy
Rob