Jet outboard vibration

[curthertel]

I just took delivery on a new Weldbilt 20/70 set up for a jet. I installed a 2018 150hp mercury 4 stroke (105hours) and installed a new jet pump on the motor. I have had this boat out 4 times. The first 2 times with one person in the boat the motor vibrated violently but in seconds got up on plane, vibration gone. Operated the boat for couple hours with no problems. The third time out I was alone vibration would not go away, idled back to trailer, contacted jet pump supplier and he said lower motor 1/4." Lowered motor and 4 trip out with 2 people in boat same vibration. Once again vibration went away and we boated for several hours with no problem. Incidentally, while vibrating, motor alarm is going off. I tried to attach a video, no luck.

 

[Branislav]

i don't know what cause your issue but you can Download video to YouTube and post link here maybe somebody ill know more

 

[Joatmon]

I just took delivery on a new Weldbilt 20/70 set up for a jet. I installed a 2018 150hp mercury 4 stroke (105hours) and installed a new jet pump on the motor. I have had this boat out 4 times. The first 2 times with one person in the boat the motor vibrated violently but in seconds got up on plane, vibration gone. Operated the boat for couple hours with no problems. The third time out I was alone vibration would not go away, idled back to trailer, contacted jet pump supplier and he said lower motor 1/4." Lowered motor and 4 trip out with 2 people in boat same vibration. Once again vibration went away and we boated for several hours with no problem. Incidentally, while vibrating, motor alarm is going off. I tried to attach a video, no luck.

I don't have a solution, but I am curious. Does the motor seem harder the start (straining) more than it did before you changed to the new pump?

Is the vibration more of a visual shake in the steering wheel or more of a loud noise or both?

After the vibration was gone after up on plane and operating for a couple of hours were you stopping and starting during this time with no vibration or were you running on plane the entire time?

Do you agree the load in the boat does not make a difference in the frequency or intensity of the vibration?

I assume being a Merc outboard you have trim control. Have you tried different trim tilt positions especially when the pump is vibrating?

The supplier recommended you lower the pump 1/4". How did you do this? Mounting holes are usually spaced 3/4" apart .Did the supplier think the pump intake was sucking air? The motor would have rev'ed to max RPM before being electronically limited. If that was the case and you did not mention it did. If you are "spinning out" maybe try lowering the motor 1" just to see what it does? I know what is involved moving the motor, but may eliminate a reason for the vibration. I have a modified jet ski that would vibrate when it was sucking air. I installed a scoop intake. Probably not an option with Merc jet pump.

 

[curthertel]

I found the problem. We removed the shift cable from the motor and rerouted to the jet pump. When we removed the shift cable it was in nutural and the computer has a rev limiter in reverse and mutual. We moved the shifter in forward and problem solved.