very hard steering after outboard change

[smee]

Hi
I have a flatacraft 5m rib, it originally had a yamaha 55 which was great, nothing wrong with it and the steering was really light, one hand operation was easy.
I was offered an evinryde etec 75 at a bargain price so obviously snapped it up. sold the yamaha and stuck the evinrude etec on the back with new steering controls.
I love it, but!

When the boat is stationary the steering is light and smooth.
Under power it is really heavy to turn with 2 hands! impossible with 1!

unfortunately, i didnt take note of the height of the previous motor....

i will try to add a photo to show height in relation to hull...

Im not sure what the prop is, its just a standard aluminium one that has quite a lot of paint on and cant see the numbers.

the trim tab is missing from the underside of the anti cav plate but i dont think this would make the steering heavy....the boat holds a reasonably straight line without it but i will get one.

At about 35mph, i am trying to trim out(up) to get the bow up but before it does the prop starts to leave the water and the revs go sky high.
It seems the hull is really digging in.





Could the motor be too high?
what prop would benefit me?
any ideas welcome?

smee

[simonl]

Get a tab - you'll be surprised how much torque it'll cancel out.

There's only so much lift at the nose you can get from an outboard, and you're sat up front. Are you sure you're not just trimming it out of the water? How does the wake look?

[smee]

I have not been able to get to the back of the boat whilst under power to look at the position of the anti cav plate but i have a feeling the prop is leaving the water.

ive only been out with the wife a couple of times and too scared to let her drive while im looking over the back!!!

i thought that the outboard mounting height looked pretty good judging by other forums/internet/pics but i am tempted to try dropping it down a couple of holes. It seems the most popular position is to have acp a couple of inches above the bottom of the hull, which i have.

The old outboard was mounted quite a bit lower but i cant remember what length the leg was and where the anti cav was positioned.

I really should take it out again and check out the height whist running before i do anything.

[two stroke mick]

Is part of the skeg broken?

[paintman]

I was wondering that too.
Looking at other pics online it does look like something's going on with the skeg & possibly a substantial amount of it is missing.

Might also be a bit high. Put a straight stick along the keel & see where it is in relation to the plate.
The Outboard Expert: Boost Speed with Outboard Engine Height Adjustments - boats.com

Basics for prop selection involve the boat normally loaded & runs at WOT.
Record the WOT revs achieved & see if that figure falls within the parameters specified by Evinrude.
BUT I'd suggest you get the height & skeg sorted before.
Clean the prop up & see what you've got.

[wellhouse]

get the trim tab as above, that will almost definitely be the main part of the problem and yes a big chunk of your skeg is missing! (should look more like this) Also i would say your engine needs lowering by 1 or 2 bolt holes (ish)

[paintman]

Didn't put this in my post above, but if there is a big chunk of skeg missing then this will also affect the steering & may well be a part of your problem.

[simonl]

Originally Posted by paintman

Didn't put this in my post above, but if there is a big chunk of skeg missing then this will also affect the steering & may well be a part of your problem.

I can't see why that would affect the steering torque, unless it's bent - does it look straight from behind? If bent I would just correct with the tab.

[smee]

yes a bit of the skeg is missing....not guilty!

looking at paintmans link, i can see i must be a good 2 inches above the motor shown.

when i get time i think i will drop it down at least two holes. looks like the simplest thing to do.

if i can get it to handle as it did with the old motor i dont mind if it goes a couple of mph less....

[neil.mccrirrick]

Most of your skeg is missing while this protects the prop it will also direct water and ease the steering. Try these guys for a cheaper repair option http://www.gmtmarine.co.uk/index.php...skegguard.html

[simonl]

Originally Posted by neil.mccrirrick

Most of your skeg is missing while this protects the prop it will also direct water and ease the steering. Try these guys for a cheaper repair option GMT Marine - Suppliers of Megaware Keelguard - SkegGuard

I think the photo is misleading - I wouldn't say most of it is missing - there's a fair chunk missing for sure, but then there's a large bit that's er, polished!

Can't understand how fixing that will ease the steering though...

[office888]

Originally Posted by simonl

Can't understand how fixing that will ease the steering though...

You're missing a large chunk of the "rudder".

[simonl]

Originally Posted by office888

You're missing a large chunk of the "rudder".

So it should need less effort to turn? Acknowledging that you put 'rudder' in quotes, I'm sure you'd agree that the rudder effects are negligible? We all know that turns are effected by a change in the direction of thrust. Knock a boat into neutral and feel how much torque feedback you get. I've driven a boat with much less skeg than that and I couldn't notice any effect. Other than prop/box protection and a small amount of lateral effect in corners I can't see that a skeg does much - certainly can't see how it can be inducing/reducing steering torque. Always happy to learn though.

[Davie]

Is there a choice of steering link bar holes on the 75?

[smee]

yes there is a choice of steering link bar holes and i thought that was going to sort it. it was on the shortest and i put it onto the longest.

I will probably get one of the skeg repair/bolt on kits but cant see that this would have such a large effect on the steering.

Im trying to pin down a new prop to try, one that will bow lift.
not stainless though, too pricey for the amount that i actually use the boat so looking fo an aluminium one...any ideas?....

im finding props very confusing! i never realized until recently that props played such a large roll in bow/stern lift as well as thrust!

Im using an outboard and prop set up that came off a 20ft merry fisher type boat so a lot heavier than my 5m rib.

[paintman]

Sort the skeg.
Fit a trim tab.
Get the engine to the right height.

THEN
With the normal load that the boat will be used with on board make several runs at WOT.
Make a note of the revs achieved.
Compare this with the recommended WOT rev range given by Evinrude for your engine.
You will then have a better idea of whether the existing prop is suitable or which way you need to go pitchwise to get the best option.

What's the pitch of the current prop?

[simonl]

I don't suppose you sold a long shaft engine & bought a short shaft one?!!

[smee]

I'm not sure about the prop size. I've measured it at 13 diameter but i can't see any thing stamped on it... I'm going to have to take it off and remove some paint for that.
I'm thinking the same about the long and short shaft. I'm pretty sure I measured them and they were the same length. I'm trying to find the old serial numbers to find out. They are noted down somewhere!
The transom bracket is not sitting on the transom like the old motor was. I have lifted it up on purpose to bring the anti cav above the hull by a couple of inches, it's where I thought best to start so I do have a lot of movement downwards.

[Iron Dials]

Is the steering difficult in both directions? Torque from engine should make one direction easy and one difficult I think.

If both directions difficult it may be a steering installation issue. (in addition to the other items you're aware of )

[JimRib]

Evinrude props usually have the prop size on the centre hub, printed round the nut.