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Jeff G.
Jeff G., Marine Mechanic
Category: Boat
Satisfied Customers: 4728
Experience:  42 years experience, Certified Master Technician, All Major Outboards, Sterndrives, Hi-Performance
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Hi, Have an Evinrude 2006 Injected 250HP outboard (not an

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Have an Evinrude 2006 Injected 250HP outboard (not an E-TEC according to the stickers RAM Etch or something) was travelling at about 20mph powered on, as the rev and speed increased started to notice a regular banging noise (every 5 secs or so) which shuddered thru the whole boat. I could see the engine was 'jumping' as such but it didn't appear that the revs were altered or like the engine was cutting out. Backed off in Rev and the issues went away. Increased the rev again and it returned. Any ideas? Bit affraid to go back out
Welcome,this question may need more than a single answer. Please post back with additional questions on this at any time.

You may have been over reving the engine. If this happens the protection system kicks in and cuts the power to the engine by cutting a couple cylinders. This is usually caused by a prop hub going bad allowing the engine to over rev. Do you know what rpm it did it at?
Another possibility is the power trim could be failing. Does the trim go up and down smoothly and quickly? Or does it jerk a bit?
I would lean towards the second item, a bad, failing hub in the propeller.
You could either have a replaceable hub or a pressed in hub. Either way your local shop should be able to fix you up.
Here is a quick test. Put a piece of 2X4 wood between the prop blade and the cavitation plate so the prop doesn't move. Remove the cotter pin and put a socket and large ratchet or breaker bar on the prop nut. Slowly try to turn the propeller shaft clockwise. If the shaft moves but the prop stays in place the hub is definitely bad.
Have the hub replaced.
Thanks, XXXXX XXXXX know what you find or if you have an additional question on this. I'll be out of the office for a few hours but will respond as soon as I get back.
Customer: replied 3 years ago.



It wasn't over reving, as the revs were about 3500 to 4000 previous outings 4000 to 5000 RPM seem fine. As for the trim yes smooth as silk.

I also tried trimming up and down during this issue and the issue remained. I can try the hub but won't be able for a few days.



Unless the rpm's were changing the engine shouldn't have been shuddering and the engine moving in or out.
Also trim the engine up with the boat out of the water, grab the lower unit and pull it sharply up and down. See if there is any play in the midsection, tilt tube or swivel bracket. Basically too much play anywhere in the midsection.
Let me know.
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