Johnson 110 1989 ex racing rib.

Bruce1 · 08 July 2006, 22:15

Be grateful if somebody knows of an extra long leg for this engine. Have acquired this formula 3 racing rib 'retribution' ( won british nationals 2 years ago). Hull has a 6 inch step in it 16 inches from the stern. It was set up for racing, and I need to get the prop lower in the water for more everyday use. The engine has been lowered right down on to the transom. It can not go any lower.It has a standard 13 x 17 prop on where as before it had a surface piercing prop. from a standing start it takes off fine, but it looses grip from ventilation as the nose comes down. Be grateful for any advice, thoughts ect.

Downhilldai · 08 July 2006, 22:46

Where does the cavitation plate now sit, relative to the level of the underside of the hull, when the engine is trimmed all the way in?

Bruce1 · 09 July 2006, 10:58

Hi,
The cavitation ( Ventilation) plate is definitely in the wrong place. If you follow a line along the bottom of the hull, ignoring the step, this line is about two thirds to three quarters up the propellor hub's diameter. Have a photo but will have to find out how to put it on the forum. The prop is sucking air in and loosing grip hence I can only think of finding a longer gear casing. Any other thoughts ? Appreciate your help.

Downhilldai · 09 July 2006, 17:41

With that set-up, it's definitely going to ventilate.
You'll either have to get a longer leg, as you're planning, or reduce the transom height - is this possible on your boat?
If the engine is a 'long-shaft', you'll need around 21" from the top of the transom to the underside of the hull.

Bruce1 · 10 July 2006, 11:52

I cannot lower the transom any more than it is. My only choice is too either
a)find a 25 inch gearbox ( its a 20 inch on it)
b) find another engine
c) Take the whole lot back to the person that said it would all work fine !!!

fast fred · 10 July 2006, 12:30

show a pic of it, maybe tranfur some weight, maybe change the style of prop.