Vibration

[system-f]

1971 Merc Type I drive, chevy 250.

I have a vibration that I cannot seem to cure. Vibration is pronounced above 1800rpm and feels like the engine is out of alignment. I just pulled the drive and I do not think this is the case. The drive does have a whine out of the water, but the oil looks good and was replaced less than 30min. ago.

1. Engine alignment was off, just checked and the alignment tool has a very light resistance but no spline marks and seats all the way.

2. new u-joints

3. one season on the gimbal bearin

4. NO WATER in belows, everything is tip-top and dry.

5. Engine compression above 120 on all 6 holes

6. Engine idles fine, no missing, pulled spark plug wires one by one while running and it dropped an equal rpm for each hole.

7. Vibration is the same under load or on the muffs, in gear or in neutral

8. Rear motor mount bushings are good, had the housing off one year ago.

I am stumped. Someone said something about new u-joints needing to breakin, but that doesn't sound right.

help? Ideas?

 

[Don S]

Re: Vibration

The drive does have a whine out of the water,

That's normal.

1. Engine alignment was off, just checked and the alignment tool has a very light resistance but no spline marks and seats all the way.

If you put grease on the alignment bar, it better have some spline marks on the bar where the splines pushed the grease out of the way. If not, you didn't get the bar into the coupler splines.

7. Vibration is the same under load or on the muffs, in gear or in neutral

What about with the drive off? (Hook your water hose to the thermostat housing where the water enters from the drive)

Someone said something about new u-joints needing to breakin,

Don't listen to them anymore.

 

[system-f]

Re: Vibration

Thank you for your help. I will try it with the drive off. I know for a fact that the alignment bar is engaging all the way because I can see the marks on the first ridge from the engine side where it is hitting the outside of the splines. I did not put grease on the bar, there was enough in the splines to see small marks when the alignment was off. I checked the alignment before pulling the drive at the end of last season and have only used the boat for 2 hours this season.

 

[system-f]

Re: Vibration

The vibration is still there with the drive disconnected. I know the rear motor mounts are good, but the front looks questionable.