Strange Vibrations

[Average Joe]

I ran my 2004 F150 all day Saturday and it ran perfectly. When I was coming in, I slowed down for a no wake zone and when I came back up on plane there seemed to be a vibration coming from the motor. It still ran smooth (no missing, hesitation or unusual noises) but I could feel the vibration/shudder through the hull.

The prop looks fine and I'm far from being a marine mechanic so I don't have a clue what else it could be.

Maybe fuel issues? prop hub? The motor has 295 hrs. Any suggestions would be appreciated before I take it to the shop @ $95 hr

I posted this question on another site and it was suggested by someone who had experienced a similar episode to treat the fuel with Startron?

 

[Grog]

Are you sure you didn't pick up anything? If the motor sounded the same and had the same power it's probably OK. Did it also seem sluggish? Run hot?

 

[Average Joe]

It ran fine Grog. I made two long runs across the bay at about 3500-4000 rpms and trolled at 700 rpm for about 3 hours. I've heard of other people having various fuel related problems (real or imagined) since the switch to ethanol blend.
I had back surgery this year and have only put about 20 hours on the motor since January so I was thinking maybe some fuel issues.

 

[gradyfish22]

Sounds like a fuel related issue. It could be the E-10. I would add some octane booster to it if you have not done so already. If the problem persists, it might be your fuel pump, that should have been replaced in 2006 if it has not been done already.

 

[BobP]

If it could be the fuel , why not rule it out?

Connect a portable gas tank with fresh fuel directly to inlet of racor if you have one, or the engine itself, effectively bypassing the boats fuel system.

Have you checked the engine and boat filter?

 

[tuxedospike]

Strange Vibe's...

I'd pull the prop and look for any mono wrapped around the prop shaft. This can cut seals and allow water into the lower unit for a lot of trouble to occur. Also drop out the lower drain bolt on the motor's foot and be sure to catch the fluid...you can see water if thats what it is. This is what happened to me about ten wears ago, Good luck !

 

[Grog]

The fuel problems I had were fuel pumps and carb rebuild. The word is ethanol eats the fuel pumps so every other year they're probably due. Both times the motors had noticably less power. If all you have is a vibration and the power is normal, I don't see it being fuel related. Does the vibration increase with RPM's? In gear as well as in neutral?

 

[Average Joe]

Maybe vibration is not th best word to describe the bucking sensation...but I don't know how else to describe it. I talked to the fellow again who recommended Startron and he fixed a similar problem on a F225 by adding 4-5oz of Startron to the water seperator, letting the motor idle for ~10 minutes and then running it for awhile at the upper range.

I'm going to try that and if it doesn't solve the problem he's going to run a diagnostic check at no cost for me.

Thanks for the replies