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Author Topic:   Optimax 135 Vibration
bravocharlie posted 08-01-2005 05:44 PM ET (US)   Profile for bravocharlie   Send Email to bravocharlie  
I recently switched from a three blade to four blade prop. When we first pulled away from the dock with the four blade, I immediately noticed a vibration coming from the prop/engine at idle forward speed. The vibration disappears at higher rpms (100+). The in gear foward idle is at 560-580 rpms. AT 650+ rpm, the vibration diminishes significantly. Vibration occurs in both forward and reverse idle.

I took the boat to the dealer today where we put the three blade back on for a test and the vibration was still present.

What gives?

Prior to switching the three blade, I never had any issues with vibration at this rpm range.

We ended up changing the plugs (the plugs needed changed anyway) to see if there was a bad plug but that didn't solve the problem.

At cruise, there appears to be no issues with vibration. Engine mounts appear to be good. There's no excessive slop or play.

Boat is 180 Dauntless w/ 135 Optimax. 75 hours total.

bsmotril posted 08-01-2005 07:24 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
Are you using the same Flo Torque hub insert in both props you tested? If it is dirty, or worn, it won't seat evenly into the prop and could cause your problem. Try another hub insert, and make absolutely certain the cavity it mounts into on the prop is clean and free of debris. Also, double check to be sure the thrust washer is installed correctly behind the prop. BillS
bravocharlie posted 08-01-2005 08:28 PM ET (US)     Profile for bravocharlie  Send Email to bravocharlie     
I used the same torque washer that was one the shaft. I didn't remove it when I changed props. I did however use the new, from the box flow torque hub insert.
bsmotril posted 08-01-2005 10:42 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
Could be the insert is defective, not molded correctly with the prop shaft centered in the piece. I've never heard of it happening, but the first rule of troubleshooting is to step by step Un-do the items that you changed and see if the problem goes away. BillS
lakeman posted 08-09-2005 06:20 PM ET (US)     Profile for lakeman  Send Email to lakeman     
I believe all or most outboards will vibrate a little at low speeds and different trim angles just the nature of the beast. Changing props may have just changed the water flow or trim angle needed to run smooth through the water. You might also look at raising or lowering the motor. Having said that, some OB models and manufacturers seem to mask the vibration better. I might add that different boats have differnet characteristics of water flow resulting in less or more vibration at loser speeds.
Clark Roberts posted 08-10-2005 11:35 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Check for recommended idle (in gear) speed. Below 600 seems too low to me. Check it out and adjust to recommended rpm is necessary. Happy Whalin'... Clark.. Spruce Creek Navy
bsmotril posted 08-10-2005 03:04 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
Nope, that is normal for an Opti in gear idle speed. BillS
bsmotril posted 08-10-2005 03:05 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
600 is normal, below that is out of spec as Clark states,
bravocharlie posted 08-10-2005 04:09 PM ET (US)     Profile for bravocharlie  Send Email to bravocharlie     
Update:
I had the hub replaced with a new one (under warranty). The forward and reverse idle vibration is still present.

The idle is around 560 to 580. I need to find out if 600 is in fact the correct (to spec) idle speed. If so, then that could be my problem.

bravocharlie posted 08-10-2005 04:25 PM ET (US)     Profile for bravocharlie  Send Email to bravocharlie     
Another Update:

I was told that the forward idle spec for the 135 Optimax is 550 rpm +/- 25.

Someone mentioned 600 rpm. Where did that number come from?

bsmotril posted 08-10-2005 04:35 PM ET (US)     Profile for bsmotril  Send Email to bsmotril     
600 is the speed in the troubleshooting chart i have that came out of a mechanics class coursebook for optis when they first came out in 1997. Go with whatever you have that is more current. BillS
sosmerc posted 10-25-2005 12:28 AM ET (US)     Profile for sosmerc  Send Email to sosmerc     
Check the propshaft for straightness.....if it's out more than .006 this could cause vibration.
Also recommend you switch to the new flowtorque III hub kit...it will smooth out the low speed "clutch chatter" that is expecially annoying with stainless props on these engines as well as 4 strokes.
Kencvit posted 10-25-2005 02:23 AM ET (US)     Profile for Kencvit  Send Email to Kencvit     
Sosmerc, What is "clutch chatter" . Thanks
sosmerc posted 10-25-2005 12:13 PM ET (US)     Profile for sosmerc  Send Email to sosmerc     
It's hard to explain, but I will try. In gear, at a slow idle speed, the weight of a stainless prop accentuates the problem...the prop gets ahead of the clutch and it rattles or bangs when the clutch catches up to the prop.
On some boats it sounds like the gearcase is coming apart!
If you bring up the rpm just a bit, the noise goes away.
If you look at a flowtorque III hub you will see that it is split in the middle and has some "give" to it...to absorb the motion or chatter. Like I said earlier, the problem is especially noticeable with stainless props on 4 strokes, 3 cylinders and L4 Mercs...engines that have a very low idle speed and are not terribly smooth. The flowtorque III does make a significant difference in my opinion.

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