ETEC 90 Prop Vibration

[gwfish]

I have a 2009 Evenrude ETEC 90 25" shaft Tiller model with a Viper 14.75 x 17 propeller. The motor works great except at idle (which is quite often with a tiller) when put into gear the motor vibrates and the lower unit geraing sound like a bunch of loose parts rattling around it is disappointing sitting next to the motor all day. This only happens at idle speed. My dealer has looked at the motor and can not see any problems...I know of one other 90 ETEC that does exactly the same thing. Has anyone else experienced this? Did you find a way to solve the problem? Is this a problem or is this how ETEC's run?

[staylor]

...change the lower unit lube- just in case you've got some chips that wore off during break-in. Next thing is to swap to a plain old aluminum prop for a day to see if its the blade shape that's giving an idle problem. When you take the prop off, check just inside the lower unit "bullet" where the turned down section on the front of the prop enters about 3/8 inch into the bullet. Look for obvious wearing of the aluminum from the prop rubbing under load. On the last 3 Evinrudes I owned all showed this rubbing from SS props. The fix was to look at the prop hub for the high spot that was rubbing and grind/file this down. I'd then put some black paint on the section I filed on the prop and run it for a while- then pull the prop and see if its still rubbing. If none of this works, then have the dealer check the lower unit for the proper shaft radial runout and axial play. He'll whine about this because its a messy job- tough!
Doug

[Hot Runr Guy]

like staylor mentions, try an aluminum or ComProp, you may be getting what is called "prop rattle", which happens in some combinations of motors and heavier stainless props. I'm not sure if the Viper is a "hub insert" type of prop, if so, Mercury has different hub kit parts available that may cure it.
HRG

[gwfish]

I removed the prop and it had an area that was a bit scuffed in the turned down diameter on the prop hub so I filed that area down (did not remove much just enough to get a smooth filed finish). I also checked clearance prior to removing the prop with some shim stock (feeler gage) between the prop hub and the gear case at the tightest spot there is something like .004 clearance however I expect there is stack up and deflection movement under power. Going fishing for a few hours today we'll see if the file job makes a difference. Thanks for the advice.

[gwfish]

Tried the prop this afternoon and the knocking/vibration is actually worse. I'm going to see if I can locate an aluminum prop to try.

[staylor]

...is it fully torqued to spec and running the correct hub insert so that there is no discernable looseness in the prop relative to the shaft? One of my current Merc Trophy Plus props used to need to be retorqued after it's been installed and run for a bit. When it loosened it started to vibrate a bit at idle. The factory increased the torque specs for it and the problem went away. As Hot Runr Guy noted it could well be prop rattle from an SS prop that your motor and rig just doesn't like. I used to run some hubless chopper props on light rigs with big motors that would have awful rattles and shakes from idle up to about 30 mph.
Doug

[FinsNFeet]

I have a 2009 90 HP Etech as well and I do not experience what you have going on. The one thing that did come to mind was the prop size. I am no expert by any means but I will throw this out there. My prop is a 13.25 X 17 SS. Could the diameter of the prop your using be too large at that pitch for the gear case?

[seahorse]

IF you grab your propshaft and push it in and out, you will hear a slight clunk due to the normal free-play. If a propeller has a blade that is just slightly off, it wobbles slightly and will allow the shaft to move in and out at dead idle in gear, making the noise. It goes away as soon as you shift into neutral.

If you increase rpms just a bit, the noise goes away because the pushing force of the prop "seats" the propshaft against the forward gear thrust bearing, thus the shaft won't move in and out anymore.

[Hub Kit]

#1 You need a prop with a removable, interchangable hub.
#2 Then use a Mercury FLO TORQ 3
#3 Your problem will be solved !

[gwfish]

Wow...learning a lot thanks everyone for chiming in.

Feels like the propeller may indeed be causing the problem. The motor is on a 618T Ranger so my first step is determining what the proper size and pitch prop SHOULD be on this boat/motor combination I have asked my local Ranger dealer for that answer (and prop nut torque spec). After that I'll start looking for a propeller. If there any Ranger 618T guys out there with 90 ETEC's it would be good to know first hand what prop works on this rig.

[bob oh]

If there any Ranger 618T guys out there with 90 ETEC's it would be good to know first hand what prop works on this rig.

you might want to post this as a separate question as I noticed on another post there are several on here with that combo.

[Hot Runr Guy]

Wow...learning a lot thanks everyone for chiming in.

Feels like the propeller may indeed be causing the problem. The motor is on a 618T Ranger so my first step is determining what the proper size and pitch prop SHOULD be on this boat/motor combination I have asked my local Ranger dealer for that answer (and prop nut torque spec). After that I'll start looking for a propeller. If there any Ranger 618T guys out there with 90 ETEC's it would be good to know first hand what prop works on this rig.
Look at this post: http://www.walleyecentral.com/forums/showpost.php?p=1148338&postcount=20

George Feder is the man to talk to, his contact info is on the post.
HRG