Evinrude 70 bad high frequency vibration

Sashap

Petty Officer 2nd Class
Joined
May 1, 2016
Messages
145
New prop been using for a few weeks. All ok until today. Such a bad vibration screws coming loose on boat and engine. Most noticeable at wot. No loss of power. Not like an engine misfire vibration but like someone installed a jack hammer. What causes this all of a sudden? Didn't hit anything. Prop still perfect. All bolts were tightened recently. Tried different prop but didn't notice change. Help please?
 

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
7,985
Usually when that happens something bent like driveshaft/propshaft or broken motor mounts. Could also be a bad bearing somewhere. Not an easy problem to guess at
 
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Sashap

Petty Officer 2nd Class
Joined
May 1, 2016
Messages
145
Could it be internal engine damage? I ran it almost an hour before I realized it was happening
 

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
7,985
Yes it could be you will have to do some diagnosing could be an electrical issue need year and model #
 

Sashap

Petty Officer 2nd Class
Joined
May 1, 2016
Messages
145
1985 long shaft with power trim
Sorry serial not handy
 

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Check the upper bearing - grab the flywheel and see if it moves laterally.

Check the propshaft for straightness - spin the prop in neutral and watch the dimple in the tip of the propshaft. If it wobbles around, the propshaft is bent.
 
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