johnson 40 hp vibration

[rkp]

I just purchased a 98 40hp johnson outboard on a whaler 13 dauntless. i had it tuned up at the dealer. The first time I put it in the water I noticed that when you advance the throttle to the first detent after neutral the motor has some vibration and chatter. It doesn't sound like gears grinding. This happens in both forward and reverse. As soon as you push the throttle further forward even only slightly as rpms advance the vibration/chattering goes away and the motor runs great. The lower unit oil was changed and the motor only has about 60-70 hours on it. Is this usual for this motor?

 

[Hooty]

Re: johnson 40 hp vibration

My guess is either a miss in the engine just as you're coming of idle or a bent prop. Have a look at the prop and see if you see anything obvious. I leaning toward the miss though and it could be something as simple as a minor carburetor adjustment. With the throttle in the detent where the engine vibrates/misses, give the choke/primer a quick bump and see if that has any effect on the vibration. <br />Get back to us and let us know what ya found out.<br /><br />c/6<br /><br />Hooty

 

[The Marine Doctor]

Re: johnson 40 hp vibration

When you shift...are you pushing quickly?<br /><br />TMD

 

[rkp]

Re: johnson 40 hp vibration

I am pushing quickly enough that I know it's not the gear grind you get if you hesitate or shift slow. The dealer sold me a stainless prop to replace the aluminum one and initially I thought it was that but i changed it back and both props have the vibration. I would have thought maybe it was a bent shaft but in at every other rpm it goes away.<br /><br />Thanks,<br />RKP

 

[Hooty]

Re: johnson 40 hp vibration

Certinally could be a bent shaft. Pull the prop off and check the runout.<br /><br />c/6<br /><br />Hooty