Vibration with new prop?

[87SunSportMikeyD]

Hey guys I finally gut the 87 SunSport out yesterday. Everything went pretty good.

My new ACME 913 prop gave me a little vibration and it's bumming me out. Starts when we accelerate past idle as a slow vibe. Gets rougher until we are on plane and then it pretty much goes away due to the rpm speed.

I did not notice this last year at all. Could my shaft be bent? Could the prop be on crooked? Imbalanced??? Should I ignore the vibe for now and board away today? Or should I take the time to put the old prop back on and see if it goes away?

Any tips, comments, ideas are welcome and very appreciated.

The power behind that prop is crazy. Haven't tried any weight yet but it make the boat feel like a toy! It powers right onto plane without much throttle movement. No problems driving above 30mph but I didn't want to push it do the vibe.

The FAE is so quiet it is unreal. Pretty much then only noise at any speed is the water against the hull and the engine inside the insulated enginebox. I would say it is pretty much as quiet as any car. I can drive behind someone and sneek right up on them hehe!

[saltare inverts]

That is frustrating to spend the money and it may not be working right. I would put on old prop and see first. Do you think it could be from your new under water exhaust. Dont you miss the sound of that v-8. I am such a horsepower lover I think I would miss that sound. Good luck.

[Salty87]

i'm kinda glad the fae's are pricey. i like the sound too so the cost is just an excuse to keep enjoying it.

that blows mikey. i've got a vibration too...and i think my rudder is leaking. always something.

anyway, putting the old prop back on is better than rolling with the new. sounds like the old one is out of balance abd your alignment has offset for it. you might have hit something and not noticed it.

i would check alignment. if you're sure the new prop isn't damaged and i doubt nettle sent you one like that, you've got something out of whack....engine alignment, strut, or shaft. alignment is a pain but checking the other 2 require more dis-assembly. alignment is really a periodic maintenance thing anyway.

i posted some procedures if you search for 'alignment procedures'. basically, you need to disconnect the coupler from the transmission and make sure the 2 plates are lined up within tolerances.

if that's good it's time to pull the shaft and strut. i drop my stuff off at my local prop shop (nettles) and there's no charge if there's nothing to fix. there's gotta be some prop shops up there.

nothing like a new prop, even reverse feels different.

[87SunSportMikeyD]

Did some more searching and someone recommended I remove the current prop, remove the square prop key, an make sure the prop isn't riding on the key. Meaning the prop has a tapered hole for the shaft and the key is a square. If the square is too far on the shaft, the prop might sit on top the key and not flat against the shaft, causing a wobble. So I will need to get a prop puller again. Sigh. I think I will just buy one.

Went out for another cruise tonight. Man that prop is INCREDIBLY powerful.

[tjonas1]

87sunsportmikeyd,
I just order my new 913 prop yesterday after reading alot of good things about it on this site. How did it affect your RPM's at crusing speed. I was looking for a prop that will pull your arms off, joking.. I run around 1200lbs of weight in my boat and most of the time have 3 to 5 people also, the old 13x13 prop just wasn't doing the job.

[87SunSportMikeyD]

tj hey honestly I have not given a full test yet since it is vibrating. I have really only opened her up a couple times and holy cow I couldn't believe it I'm talking SIT DOWN or you will be sat! Jerk your head back strong. Unbelievable difference. Now I haven't really driven around a whole lot at speed, and I haven't ran ANY weight yet, so I can't comment on that aspect. But it did hold speed very well at slower speeds.

I will be buying a prop puller (no more borrowing) and a new exhaust blower in the next couple days. If I can get the vibration figured out I will do a full report.

My old prop was a 13x12. Boat also came with 13x13.

Oh and about your question of RPMs at cruising speed... NettleProps.com told me that since our boats don't have RPM limiter never go over 4500RPM or our new prop could cause engine damage. But that is crazy fast anyways. I opened it up to about 32mph and the RPMs were actually only like 3500 so it isn't a huge jump in RPMs. I didn't notice the engine working any harder, really. Not without weight anyways. Or maybe it was JUST SO DANG QUIET with the FAE I didn't even notice! HAH!

Here's a pic of the new prop and FAE (yes again and yes backwards in the pic doh I will have to get some new ones) and refinished teak platform with patriotic flag to make this thread more entertaining!

[mapleleaf]

that platform looks ccccclean......

[wotan2525]

I agree with everything already said.... something is wrong. My guess is engine alignment or a bent prop-shaft. The prop should be OK unless you hit something right away (which is possible!)

No need for a prop-puller. Heat it up with a blowtorch and you can pry it off with a two by four or some gentle coaxing with a rubber mallet. My prop-guy just heats it up with an acetalyne torch and it POPS off. If you do this.... make sure to leave the nut on a couple turns so the pop doesn't fly off!