83' 70 hp mercury excessive vibration

[Cookingkahle]

Hi everyone, I have an 83' 70 hp mercury outboard. The motor runs great and has very low hours and is I practically new conditioning. At idle and under power at low and mid RPM up to 3000 there is a good amount of vibration. Any ideas on what yo lil for.? Is this common with these 3 cylinder outboards. Prop is original and never had a ding.. thanks

 

[Cookingkahle]

I will say that it vibrates more under power and not so much at idle..

 

[merc850]

Can you run it on muffs in driveway? If so look at the prop while it's in F running slowly; you could also take the prop off and look at the shaft to see if it's bent. Don't rev the crap out of it.
If all looks good maybe a plug is not firing up to par.

 

[racerone]

First thing to do is a compression test.

 

[Cookingkahle]

One getting full rpms also I'm getting up to 36 mph with my 15 ft bowrider?

 

[Cookingkahle]

Thank racerone! Will do.

 

[Cookingkahle]

Can you run it on muffs in driveway? If so look at the prop while it's in F running slowly; you could also take the prop off and look at the shaft to see if it's bent. Don't rev the crap out of it.
If all looks good maybe a plug is not firing up to par.

Thanks for the info, I will do this tomorrow and fill you in on what I find out

 

[The Force power]

Can you run it on muffs in driveway? If so look at the prop while it's in F running slowly; you could also take the prop off and look at the shaft to see if it's bent. Don't rev the crap out of it.
If all looks good maybe a plug is not firing up to par.

when you have the prop off and the shaft hopefully turn out ok, lay the prop on a flat surface & measure the distance from each blade to the surface do this on both side of the blades

To check the prop-shaft you kinda would need a dial-indicator (unless it really bend) it maybe better with the prop on as that magnifies a/the "wobble"

good looking motor by the way, looks mint!!

 

[Cookingkahle]

when you have the prop off and the shaft hopefully turn out ok, lay the prop on a flat surface & measure the distance from each blade to the surface do this on both side of the blades

To check the prop-shaft you kinda would need a dial-indicator (unless it really bend) it maybe better with the prop on as that magnifies a/the "wobble"

good looking motor by the way, looks mint!!

I'll check everything today and post what I find, thanks man!

 

[Cookingkahle]

So I've checked a few things and found the rubber o ring on the under cowl fuel filter was missing which is letting air into the fuel system. I wondered why it was difficult to get the bulb to prime.. the new ring an filter arrives today and I'm putting it on hopefully this solves the issue