Eric - Maximum coupler runout?

Thanks Pete & Eric.

Well, I feel I went to a shaft alignment class today because I learned a bunch more about this.

I thought that if the coupler gap varies, that was due to a bowed shaft, so yesterday I measured the shaft (dial indicator mag base to trailer), & by golly shaft was bowed. This was without the coupler bolts tight.


Today I decided to split the difference on the gap, as it was on & off only to one side.

So I moved the front of the engine up & over 1/16 inch. The coupler came in to .002 inch all-around, any position. Better yet, the shaft runout dropped to about .004 inch. So apparently there is interaction, bow causes coupler MA & coupler MA causes bow.

How it changed from this spring's alignment I don't know (it was within .003, didn't change it from last year), but it is now running sweet again.


Thanks for the advice on new shaft & straightening, I'm sure I will need that in the future, but I'm good for now.

Thanks Eric - I am going to re-align for best fit & head for the lake. Supposed to be 'oppressive' humidity today, sounds like nice boarding weather!

Pete is there good success rate in straightening, or am I better off buying new? Do these things have a memory & the bow will come back?

It is not off very far but I like a smooth ride!

it would be hard to bend a coupling, even scuffing a sand bar will whack the shaft. I have a shaft at the shop i think is a 51 or so, but could cut and key the only thing is it doesnt have a fitted coupling...and since we dont have a site sponser that handles A.R.E shafts (double taper) you could call the guy that makes them and have one NDA, I believe they are worth buying now because of the price. the place is called Elberts, 800-541-4962/503-864-2445
as for your Vibration, theres guys out there that thinks those vibes are normal and deal with them....long term i think you will see damage, dont ruin your days off

Correct Parts   I got a single taper with a new coupler installed by someone who knew what they were doing. They also faced it and sent all new hardware(Billy insisted). It's beautiful workmanship. When I lapped the prop, I saw that it almost didn't need it.

That said, there's something to be said for the dual taper. I haven't tried one of those, but some maintenance would be easier...especially on a shallow river.

As Pete pointed out, I already had to pull the engine to clean the bilge.

Greg, that is the message I expect - it needs to be straight or else it vibrates!

It was a new shaft last year, so something bent it.

I am just hoping I can limp by this week - waited all winter to do our summer thing, finally hitting 90.

PS, where did you get your shaft?

if the shaft was not spinning I highly doubt any damaged was made to the underwater gear for drifting into a tree. maybe you didnt take it all out and messed it when you put the boat back in gear but it seems odd too.

Eric - I'll skip the long story for now -- My shaft now has about .010 bow, which manifests itself as .003 gap at the top of the coupler at a certain shaft clocking. If I turn the shaft 180, then the gap goes away (.003 feeler won't go in all the way around).

I am thinking of re-aligning to average this error out the best I can.

It has been like this for a few hours, the vibration is getting worse, now noticible as soon as I put it in gear.

When we were surfing yesterday it was really sounding off.


Is it possible I have damaged the tranny output bearing already? If it is already toast, will I cause more damage to run it this way another 10 hours? I have the week off & this was supposed to be wakeboard week!

For the rest of you guys, what happened is:   
last week we were drifting (motor off) down the river with the current, taking a break. Then the boat lurches, & spins to a stop.   We are hung up on a sunken tree snag!    We got off of it with a bunch of paddling. There is no damage to the prop that I can see. I am wondering if the tree branch somehow caught the shaft & caused this bow. My son remarked that it felt rough immediated after this happened. The vibration is now getting worse.

Amazing how these things creep up on you, we try to be so careful!