OUTBOARD MOTOR VIBRATION ONLY AT LOW SPEEDS

fdheld34 · #1 09-21-2009, 11:39 AM

My 1997 Johnson 200 hp vibrates at low speeds....not at idle and not at medium to full throttle (dissapears completely and runs without vibration). What could be causing this vibration??? The vibration does not affect the performance in any way and no loss of power whatsoever...just annoying as heck! I do have a stainless steel prop and it does have a couple nicks and slight bend in one blade...could this be the culprit????..or is it something else
How to troubleshoot etc. etc. would also be appreciated..or
any help. thanks
-FRED

76Red18 · #2 09-21-2009, 01:40 PM

Has it always done it or is it new? I lost the pin (don't know it's proper name )that adjusts the down tilt position and when tilted all the way down would do just as you described. Bent prop would cause that also.

Bigshrimpin · #3 09-21-2009, 02:06 PM

There is a very noticable difference b/w props. My mirage plus 15 1/2" 17P has a LOT more vibration than a 17P highfive at idle speeds or even an aluminum 14 1/2 17P. Mirage Plus was brand new in box.

fdheld34 · #4 09-21-2009, 02:37 PM

Thanks all for input......
this is a new to me rebuilt motor and I got prop from my neighbor..believe it is a 15x17p (again stainless but dont know the brand) The motor has good compression spark etc.
I was wondering if I could run on hose with the prop and put in gear and push throttle until I felt vibration and then do it without prop on motor to see if a difference....would I be at risk of damaging motor by putting in gear and revving up???? without being in water and without prop on shaft?? I will look into having prop balanced straightened etc. but want to run some type of test first to see if this is the culprit...did search on google and no real definate test has come up for this problem!
Thanks again
Fred

Bigshrimpin · #5 09-21-2009, 04:12 PM

Put the boat in the water. Based upon my experience . . . heavy large diameter 3 blade props seem to vibrate a lot more than light weight aluminum 3 blade or 4 blade or 5 blade props. I have an explanation . . . but that is just my observation.

gofastsandman · #6 09-21-2009, 04:16 PM

Hey Fred,
Glad you`re not being a stranger. You need resistance when going into gear or your lower unit will be mad at you. Bobby Soles Prop service in Riviera/ Mangonia has a pretty good rep.

Greno · #7 09-21-2009, 04:55 PM

My 94 Johnson 175 vibrates when trimmed all the way down. The vibration is not violent or anything just a shimmy. I have no pin.

fishhuntNC · #8 09-21-2009, 01:43 PM

The bent prop blade is probably it.Take it of and take it to your local prop shop.Most boatyards have one.Thats my guess anyway.

ggreeby · #9 09-23-2009, 02:55 PM

Hi. 2 cycle engines do not have very strong vacum at low speed /high load with carb well open, so they set the mix rich under those conditions. When the prop is matched to the Hull design , & engine power correctly, this is just what you need when climbing on plane and not leaning out causing engine problems. Everything in life is a trade off, and with the various combiations of Hull, Engine, Prop, and load, there is little comonality. So after you find nothing wrong with how your engin is working, either live with it, or try different props. George.

McGillicuddy · #10 09-24-2009, 11:09 AM

Gee Fred,
Your old blue boat looked like it had good vibrations...from a merc.
Obviously if this other "new" boat has a bad vibration it must be the new boat

I remember someone posting that life's to short to have and ugly boat...head check, man

Really, I think the prop dings could have an effect but ggreebys point regarding 2-stroke vibes is familiar. they don't want to put around - they want to run... maybe Bigshrimpin or Fr.Frank will shed more light on that...