No Power to Water

[abudhabicruiser]

I have a 31 foot fibreglass boat with 2 x 200HP Johnsons on back. Year 2000. Until last year the boat went well (about 42 knots at full power). About a year ago, I started experiencing a problem - one engine would race - from a steady 3000 rpm to maybe 4500rpm. Lots of action and churned up water at back but the boat would not go forward at the proper speed - like an old tugboat. Local Johnson agent reckoned one or both of the shock absorbers/prop bushes had gone, and told me that the rubber shock absorbers mounted in the props were not available for Johnsons, so I changed both aluminum props for new stainless steel props. 1100 bucks. Same problem - boat sometimes goes OK; sometimes it settles in the water with both props churning a lot of water but no power being transferred to the water. I haven't hit anything, and propeller blades show no sign of cavitation. Engines have just been fully serviced, but same problem.

Help.

Abudhabicruiser.

 

[Bondo]

Re: No Power to Water

Lots of action and churned up water at back but the boat would not go forward at the proper speed

Ayuh,... Did you untie it from the dock or bouy,..??

My 1st, Best Guess is,...
The hull is Covered with Growth....

 

[steelespike]

Re: No Power to Water

Something is disturbing the water flow to the props.Barnacles something added like trim tabs a major change in weight distributation in the boat.
Absorbed water perhaps?Is the transom or motor mount in good shape?

 

[Knightgang]

Re: No Power to Water

As I started reading, I was going to say spun props, but it sounds like that issue was addressed with new props. I am inclined to agree with Bond-o that there is growth on the hull or something that has severly disturbed the waterflow to the props... Is this boat kept in a dock slip?

 

[abudhabicruiser]

Re: No Power to Water

Boat was anti-fouled 6 months ago, and it's perfectly clean. Boat is moored in the water permanently. Transom is in excellent condition. No trim tabs are fitted. The boats is about 7 years old with no damage or blemish of any description. Oh..... and the line tying it to the dock broke a while back - thanks for that.

 

[Knightgang]

Re: No Power to Water

Stabbing the dark here with a really dull knife, so forgive the seemingly redundant questions...

Has has the Lower Unit maintenance been on these engines? Are the LUs making any noice, that you can tell. Might be hard to hear over 4000rpms. If it was not the props, but the engines are still running strong RPMs, then it has to be something in the driveline that is not connecting properly and carrying that load to the water. Could be something in the LU or further up, like where the Powerhead connects to the Driveshaft. I suspect you have issue in the LU gears, but can't be sure. Let us know anymore information that you can...

 

[steelespike]

Re: No Power to Water

Something has got to be going on with the props.
Not fitted correctly, Wrong size hubs,Or somnething with the mount or boat. Props don't just start venting for no reason.If the props didn't soilve the problem Something in the lowers is disturbing the water or the exhaust.
If your in salt water perhaps something in the exhaust has corroded away.
Obviously something common to both motors.