Prop Size ?

[Joker29]

With a DCB Mach 22, I'm running a Bravo 26P and am noticing some vibration in the boat once I get to around 50 and it seems to lose power or the ability to increase speed at 70ish. Could prop size or type of prop have something to do with this? All internals of the lower have been checked out. Just thinking out loud until I take it to a professional.

Thank You,

[phillnjack]

is there any nicks in the leading edges of the blades ? and is your propeller shaft dead straight. ?

[Joker29]

is there any nicks in the leading edges of the blades ? and is your propeller shaft dead straight. ?

I've had the lower off and looked at by a few. First guy says its the bearings, second guy says the gears are pitted and its gonna grenade, third guy who I trust shows the gears and bearings, nothing wrong with either. Switched lowers and same issue. Prop was cleaned up prior to all of this, no damage. It's like a rumbling vibration, nothing that big but its there. I can see the motor moving around a bit but I'm assuming thats normal. Third guy went out with me and thought there was a bit of slip and maybe the motor could be moved down, but it's at the lowest point.

[phillnjack]

are you sure its not an engine mount problem ?
if the mounts are sloppy this could cause an excessive vibration build up, and if your seeing the motor move this could be the problem.
if you have solid mounts then maybe one could be broken or come loose ?

just a thought

does this do this with other props too, or just this one ? if just this one maybe the bush is moving around under high pressure ?

[Joker29]

are you sure its not an engine mount problem ?
if the mounts are sloppy this could cause an excessive vibration build up, and if your seeing the motor move this could be the problem.
if you have solid mounts then maybe one could be broken or come loose ?

just a thought

does this do this with other props too, or just this one ? if just this one maybe the bush is moving around under high pressure ?

This is my first outboard, so I'm not sure where the mounts are. Assuming I can't see them in this picture as Ive checked these. Thank You.

[David]

Have you tried a different prop?

[RIVERRUMMER 70]

does the motor turn full wot rpm....6500?
will it keep gaining rpm after 70 mph or motor wont make rpm after that?
what is the rpm when this all goes to ****.
maybe you are loosing bite at 70 .....if the motor keeps gaining rpm.
or you just on the limiter ....need more info!
max rpm with this setup...
rpm when vibration starts...
rpm @ 70 when she wont go any faster....
has the powerhead been apart or worked on .
tried diff gearcase but same prop?
try diff prop on diff case and see what happens.
what is current motor height?

[Joker29]

does the motor turn full wot rpm....6500?
will it keep gaining rpm after 70 mph or motor wont make rpm after that?
what is the rpm when this all goes to ****.
maybe you are loosing bite at 70 .....if the motor keeps gaining rpm.
or you just on the limiter ....need more info!
max rpm with this setup...
rpm when vibration starts...
rpm @ 70 when she wont go any faster....
has the powerhead been apart or worked on .
tried diff gearcase but same prop?
try diff prop on diff case and see what happens.
what is current motor height?

Most of your questions I cannot answer as I'm not sure of the rpms when the vibration comes in. I did not try a different prop with the new lower but I remember when he started the boat on the trailer I could hear the prop hitting metal to metal but had no idea if this was normal. The motor is at its lowest setting and the cone lines up with the lowest part of the boat in the center. I spun the prop last night manually and noticed the gap variation between the prop and lower unit differs as you can see in the pictures I'm attaching.

[rock]

Bent prop shaft.

Rock

[Joker29]

Bent prop shaft.

Rock

Can this cause a vibration in the boat?

[CNC_Guy]

Yes.

[RIVERRUMMER 70]

Vibration followed the prop its not the gearcase.
Get a diff prop and try it.
Cant be propshaft if the vibration was still present when he tried a diff gearcase.
Unless the second lower had a bent propshaft also.
Only thing he didnt try diff was the prop.
That prop has a bad hub.

[phillnjack]

agree 100% with above, the hub looks to be bad.
had this once and couldn't believe it was this as the other prop I had was the same.
then got lent a good prop and it was night and day.

definitely try a different prop, and then go to a prop shop and get that one re-hubbed.

is this by any chance a removable flo torque prop hub ?

[rock]

I should learn to read more betterer. Missed the lower swap. My first inclination was the hub but I have never seen a hub so bad as to allow side to side movement. Usually they just slip at a point under load which it sounds like it is doing but again I have never seen one that loose. I would also suggest taking a close look at the thrust washer.

Rock