Prop or motor ?

[DAN M VAGOS]

Hi all I just got my new to me boat in the water tonight. 2000 four winns 170 Horizon. The motor is a Johnson 115 horse which is also 2000. Got it to the pond after running it in my yard and doing all my checks on the boat. Seems to run great but I noticed when I was leaving the dock at very low RPM it seems like the motor was skipping or the prop was out of balance. Now she takes off and gets out of the hole with no skipping at all and when trolling at very very low rpm's it's also pretty smooth but when I reach 800 to 1000 The steering wheel starts to shake in the boat starts to shake. Just like a tire on a car if that's out of balance if I give it more RPM and go a little faster the shake goes away completely. It Really does not seem like the motor skipping I have rotated the prop out of the water and it seems to be straight but the prop does have a few small dings in it. Do you think I'm dealing with the prop problem thanks. Also what should the rpm range be of a Johnson 115 she seems to be about 5400 when on plane.

 

[jakedaawg]

CAn you post a video of problem?

 

[DAN M VAGOS]

Going to post s vid or two on YouTube the name will be danjohnson

 

[DAN M VAGOS]

kind of a tough video it is still burning off some of the fogging oil. Have not checked to see if the boat has a fuel filter don't ask me why I didn't go to that first Lol .

 

[jakedaawg]

I would suggest running in a much deeper bucket 1st off. Next, I would put new plugs in and get the fogging oil burned out. Then, if problem doesn't improve I would clean the throttle bodies.

 

[DAN M VAGOS]

I did burn off the oil and it did run a little better but it still has the vibration. Should the motor run smooth at idle my old 70hp Jonson vibrated like it had a piston missing but it always ran good at troll speed.

 

[jakedaawg]

A model # would help. Is that an OIS ignition?

 

[DAN M VAGOS]

No Title

 

[DAN M VAGOS]

I don't know how much gas was in the boat from a year ago but I do know he put 10gl of 93 in it the day I picked it up. Just wondering if I should just try to use it up and just run good gas and the Starbrite fuel treatment and see if it clears up.

 

[jakedaawg]

I don't know how much gas was in the boat from a year ago but I do know he put 10gl of 93 in it the day I picked it up. Just wondering if I should just try to use it up and just run good gas and the Starbrite fuel treatment and see if it clears up.

If at all concerned about the fuel run on a test tank with known good fuel and hose. Always remmeber that adding 1 gal good fuel to 1 gal bad fuel makes 2 gallons of bad fuel. Period. Where I live nobody uses premium so it usually sat in the gas stations tanks for a long long time. Rec fuel is best, regular is acceptable.

I seriously doubt the prop is the cause of your shaking considering it is only at one specific RPM range.

I lean towards the off-idle circuit of the carb in conjunction with the throttle body. Clean both. Do a search on here for it and you will find many post/threads.