VIBRATION!

[BoHawg]

OK, can some of you old salts out there give me some advice? I have GPU that has been running pretty well...until yesterday. I have no idea why, but at about 1200 rpm's, a strong vibration is coming from the motor. When I go above 1200 r's, the vibration is still there, just not as bad. Anyone seen this before or have any advice for me? Thanks in advance.

 

[duckluv26]

if you have a composite prop, i'd start there. make sure its still tracked. if it is, pull it off and weigh the tips and check for water.......i'm sure many other people have had that problem and it may be something else. but, thats where i'd start.

 

[Anonymous]

Agree with Duckluv, but also have you checked your motor mounts?

 

[swamproot]

sounds like rear main bearings have wallered out. this happens easily on them gpu's and espicially if your oil lines have been installed on the lifter gallies by the crankshaft. the proper placement of the oil cooler lines is up top left side of motor where the original cooler was mounted. most unknowling mechanics plug them holes up and remove the 2 set screws by the crankshaft and run the lines from there. when doing so you starve the rear mains of oil and within 100 hours the bearings are trashed.
them gpu's have much smaller bearings then aircraft motors.
you have to tap the holes in the orignal place is why most mechanics opt to hook up the oil lines on the oil gallies its a easy quick place to hook them up to. however the after effects is the cost of rebuilding the motor.
hope i have described the condition so you understand that the oil cooler lines hooked up wrong they come out the rear of the engine by the crankshaft on each side of the case. them set screws are installed there after the lifter gallies have been drilled out and not for oil cooler lines.

 

[Skeeter]

Swamproot,very interesting I will be checking into that info.I currenently have a 520 conversion and I have my oil lines run from bottom corners of block.Biulder never said anything to me and he has been biulding for I know of over 30 years.Good info

 

[cowboy]

Yeah Swamproot,
Good post. I learn something just about everytime I come here.

Let us know what you find out there Skeeter!

Airboats / aircraft never really get a chance to idle.....
never thought of that before. Not that way.
Makes perfect sense.

 

[Anonymous]

Yup. Under load all the time. Great information. Thanks, Felber.

feather

 

[Airboatcapt2]

If you have a wood prop you need to check it for water damage. Could be a serious problem.

 

[BoHawg]

I do have a wooden prop and I'm headed out to check everything listed here, tomorrow. Thanks for the ideas and replies

 

[Airboatcapt2]

Any finding yet?