Outboard rigging

codprawn · 16 November 2004, 16:46

Apparently it is usual to install a single outboard (225) a couple of inches offset to counteract torque effect. Would this still be the case if trim tabs are fitted?

obviously the torque effect could be counteracted by lowering one tab but would this mean there is then always drag present with the resulting lower top speed/worse economy?

Any advice much app.

Cookee · 16 November 2004, 16:59

Just out of interest which boat is this engine going on?

swginn · 16 November 2004, 17:12

Good article on rigging an outboard by Paul Lemmer

http://www.ribmagazine.com/articles/...icaladvice.htm

codprawn · 16 November 2004, 19:25

A lot more complicated than first appears - in fact a bit of a black art to get it just right!

The boat is an 8.5m. Will post photos when it is finally ready - custom build so taking rather a long time!

Turbodiesel · 19 November 2004, 19:08

It will also depend on the shape of the hull, deep v hulls are different to a shallow v. Its hard to say how much offset you need without seeing the boat. The offset allows the boat to sit flat when your going along on the plain. The Trim tab will counteract any steering problems eg if the boat is pulling to one side you can adjust the trim tab to help keep it in a straight line. If you get the offset right it should steer in a straight line though!!!.

Wayne Rogers · 19 November 2004, 21:54

My engine is fitted bang centre with out any problems,however on my last Rib a Valiant Patrol 5.2 Deep V Hull fitted with a 90 Ficht I had to move the engine over 2 inches to get it to handle properly.

stm · 03 March 2005, 19:31

Hi Friends
I own a Selva 510 with F100 and I look for advises for Offsetting the engine.
I read aubout center up to sev Inches - so I am confused

can anybody give me advise how to offset MY engine??

best
martin

Searider · 04 March 2005, 08:57

Was speaking with a hard boat racer last year about offset. He said that he has achieved the best speed with the engine on the centreline and the boat ballasted to counteract the propeller torque expected on the day. With the engine offset it can try and make the boat go diagonally through the water which costs speed.

My Avon (5.4SR 90hp 2 stroke)has the engine 1.5" offset to starboard. Gives it good handling but it does feel as if its trying to go a bit diagonal when going over 30 knots lightly loaded.

The Scorpion (6.5m 150hp Optimax) has the engine offset a bit (not measured but guess about 1.5") to starboard. Feels fine. Not as lively as the Avon.

I think that it is more important on light, deep vee hulls going over 30 - 35 knots.

Perhaps some of the racers on here who may have experimented might like to comment?

Regards

Cookee · 04 March 2005, 09:49

Quote:

Originally Posted by Searider

Perhaps some of the racers on here who may have experimented might like to comment?

Regards

I think you'll find most current raceboats have thier engines in the middle, in Offshore lifters which raise and lower the engine are common - the idea is to raise the engine as much as possible whilst retaining sufficient water pressure and of course control to reduce drag. In corners the engine is lowered for more control and then raised for the straights. Engine heights and offsets are always different for individual hull and engine combinations.

Hope that helps?

Searider · 04 March 2005, 10:15

Cookee,

Are there any disadvantages to mounting on the centreline if the boat is ballasted to counteract it - ie batteries etc on the starboard side?

Regards

Cookee · 04 March 2005, 10:25

Quote:

Originally Posted by Searider

Cookee,

Are there any disadvantages to mounting on the centreline if the boat is ballasted to counteract it - ie batteries etc on the starboard side?

Regards

As I said all boat / engine combinations are different but the way we set up the race boats is to have everything as far back as you can get it and on the starboard side.

Of course we have a bow tank for when we are going upwind in rough conditions so you might not want everything up against the transom!

Mark Halliday · 04 March 2005, 15:22

Quote:

Originally Posted by Searider

Cookee,

Are there any disadvantages to mounting on the centreline if the boat is ballasted to counteract it - ie batteries etc on the starboard side?

Regards

Could this also explain why most builders stick the helm to starboard in a side by side setup? I know I weigh a lot more than a couple of batteries

Cookee · 05 March 2005, 09:59

Quote:

Originally Posted by Mark Halliday

Could this also explain why most builders stick the helm to starboard in a side by side setup? I know I weigh a lot more than a couple of batteries

Quite possibly - the other way of looking at it is that with the paddle wheel effect, coming along side Starboard side to is easier to see the dock?

Turbodiesel · 06 March 2005, 16:15

Yeah, have a look at the 5.4m searider the console is very offset to counteract the torque.

stm · 06 March 2005, 19:38

Hallo All
Thank you for the lot of advises - so I see, I have to consider a lot of other possibilities to counteract the torque. still

best
martin

stm · 11 May 2005, 06:48

Hi all
after a long time thinking and thinking I set the engine 20mm to starbord(right).

when testing I was a little disapointed about the effect.

the boat tends to go into a rigtturn by itself, and I have no chance to combensate with the trim-anode.

best effect is by trimming the engine out until the boat goes straight.

in all I think, I did something wrong, as the performance became worse.

so: pls give me advise - my plan is to move the engine back to center.
best
martin