Is this the right outboard setup ?

[reetzy]

Hi, just bought a 490 freedomsport with a 75 honda not long ago and seem to be having issues with cavitation (sucking air) when doing sharp turns at high to medium speed. I have dont some research and want some confirmation to what i think is wrong. I have attached some pictures to show the current way the out board is mounted but i think it needs to go down one hole on the mounts, what do you guys think?

Oh btw first post ;D

[Chimo]

Hi reetzy

If it was mine I'd go up one more hole, fit a foil and see how it went. Probably fiddle with in and out trim when on the move too. Plate and foil should be above the surface when trimmed out and runnning correctly.

Within reason the higher the better and more economical too. Also many will suck air if your trimmed right out and don't have a foil fitted when turning hard.

Unless your about to hit a shipping container (and they float about 2 or 3 inches under the surface) don't turn as hard either!;)

Cheers
Chimo

[finga]

Is the steering heavy?
I reckon up a hole to start.
Best gauge is that the cav. plate should be just flusj or a bit above the water when planing.
:)

[peterbo3]

When you are turning hard, is the motor trimmed right out? This will cause ventilation. Solutions are to turn wider, or to throttle back in the turn, or trim in. The height you have now looks OK to me.

[foxx510]

I'm not an expert but it looks like it's within what the handbook says re setting height. I wonder if it's more to do with the keel running all the way to the back that is digging a hole and causing the cavitation.

[Spaniard_King]

That setup should not be cavitating!!!

What trim angle is the engine when you are experiencing this problem??

You may have a prop issue not an engine height issue.

I would be fixing the cavitation/ventilation issue before changing engine heights.

have you talked to the dealer about this... new boat.. he should help you out

[reetzy]

Hi, thanks for the responses, i have to have the engine trimmed all the way down (so it bottoms out basicly) otherwise its even worse. I spoke to the dealer i got it from and said they will look at it at its first service which is only around hours away. Steerings is heavy unless its plaining. The dealer said they usally fit a wedge in the top mount to trim it down more, they said they are doing it to motors like this now. Does this shead anymore light on my problem?

[Spaniard_King]

Reetzy,

the engine is not fully trimmed in. I am a Honda Tech! if thats as far as it will go you have a trim issue!

[trueblue]

That setup should not be cavitating!!!


I would be fixing the cavitation/ventilation issue before changing engine heights.



Agreed... Suggestions to lift up the motor are only going to make the problem worse. Sort out now why it is getting either cavitation or ventilation.

With that engine height, you should be able to trim in and not have ventilation on reasonable turns.

What speed are you having the trouble at, or is it at all speeds? And how tight a turn are we talking about?

cheers

Mick

[FNQCairns]

Gotta agree with most of the above except chimo (good god man head toward the light;D or you can never cross over8-):P;D). Don't go down but settle into the boat for a while, its a light boat with a centre keel they never turn real well, my light centre keel boat turns like a cat, over propped can increase the problem.

It's good just the way it is, think you have the trim pin set one hole out??

If you need ski like turns then you will need to go down to get it but for us constant throttle and heading fisho's covering long distances a little cavitation in pleasure boat type turns means good range and cheaper boating, on average if we need a ski like turn to miss something, we will probably hit it.

cheers fnq

[foxx510]

Gotta agree with most of the above except chimo
It's good just the way it is, think you have the trim pin set one hole out??

Looks to me like the trim pin has been taken out altogether. It doesn't look like it's trimmed all the way in in those photos though.

[Spaniard_King]

trim and tilt Honda's don't have trim pins.. hence you use the trim and tilt to select the required trim..

[FNQCairns]

Yeah I think you are right Fox, will be interesting to know why that's all it will give. Combined with some transoms that are a little too vertical could gang up on a person.

cheers fnq

[FNQCairns]

trim and tilt Honda's don't have trim pins.. hence you use the trim and tilt to select the required trim..

Gary, why are the trim holes there? Saving money and part numbers from the manual trim versions??

cheers fnq

[Spaniard_King]

Scott,

they use the same stern brackets on a few diff models. saves on diff moulds... and wait for it.. they are lighter :)

[Luc]

From the photos, the engine has power trim & tilt so I fail to see the need for a trim pin!!

My 25/4 yammy has power T&T and has no trim pins.

Engine height looks OK to me. Maybe needs wedging or I'd experiment with upping the engine one hole.

As far as dealer help, I'd be taking one of his suitably experienced staff for a spin.

Luc

[reetzy]

Sorry for not explaining the pics better, its only trimmed down to give an idea on where it sits in relation to the keel. When towing a skier or tuber etc i have to have it trimmed all the way down, if i trim it up she will over rev. The dealer said it might need wedging. Suppose i just wait and take them for a spin.

Types of turns are tight as i can realy, turning around to go back and pick up the person in water etc.

Im no boat expert but have a fair amount of mechanical knowledge from my trade and it is sucking air, when i turn say at 3/4 throttle it will free rev until i back off.

Again this is only in turns, have been out the front fishing and goes fine, just when turning heavly. Any other tests or photos i could do to help show it a bit better? Thanks for all the responses so far ;D

[foxx510]

trim and tilt Honda's don't have trim pins.. hence you use the trim and tilt to select the required trim..

That makes sense. They do have them in the smaller tilt and trim models though, our Honda 25 pt&t still has the pin. The manual says to set it so you can't trim it too far in. I thought they might be referring to the manual tilt models, but the pic is of a pt&t motor..... Anywho, that's not really got anything to do with the cavitation problem... ;D

Maybe you are just turning too fast for the hull/prop/outboard to stay in a clean flow of water. It might just be the limit of the setup.

[trueblue]

you might want to also look at some cupping on your prop.

Only problem is that what will turn nicely on heavy turns will be less fuel efficient...

Its all a matter for choosing your priorities.

cheers

[Luke G]

A good prop can make a huge differance. See if you can try a s/s.

[Chimo]

Hi FNQ

Am I on the right track ...........seaching for the light.............?:-*


Cheers
Chimo

[Chamelion]

I've been having the same issue. I need to trim down and back off on speed when taking turns otherwise the prop spins faster and the boat slows down.

I also seem to be having trouble keeping the bow of the boat up and out of the water. She's making more spray than other boats seem to and playing with the tilt trim does not very much at all. I get to much over 1/2 on the guage and she starts free spinning like when I take a corner too tightly at speed.

Picture of my boat in the water at full speed and trimmed out to follow...

Is yours similar in issue? Does anyone have advice?

Cheers :)

Matt.

[foxx510]

Chamelion, maybe you need to drop your outboard down one hole on the mounting bolts. Do you have a photo of the setup out of the water?

[FNQCairns]

I've been having the same issue. I need to trim down and back off on speed when taking turns otherwise the prop spins faster and the boat slows down.

I also seem to be having trouble keeping the bow of the boat up and out of the water. She's making more spray than other boats seem to and playing with the tilt trim does not very much at all. I get to much over 1/2 on the guage and she starts free spinning like when I take a corner too tightly at speed.

Picture of my boat in the water at full speed and trimmed out to follow...

Is yours similar in issue? Does anyone have advice?

Cheers :)

Matt.

For the straight line stuff...What size boat and engine, what RPM are you reaching? and at what speed.

A higher engine will allow more bow lift, propped badly reduces maximum thrust, thrust is needed to raise the bow, dropping the engine increases drag which increases slip at speed, slip is why the bow will not raise at speed.

A good setup mess = adequate power, low engine and not reaching on or above manufacturers recommended RPM with a full load onboard...if you have one of the above you need to fix all of the others or you will go around in circles...possibly end up fitting a foil.

cheers fnq

[Chimo]

Hi Matt

Where was you cav plate sitting in relation to the water surface when that pic in post 22 was taken?

Knowing that will make it easier to suggest possible options.

Cheers
Chimo

[Chamelion]

Chamelion, maybe you need to drop your outboard down one hole on the mounting bolts. Do you have a photo of the setup out of the water?

It could only go down a single hole.. I'll work on getting a photo.


For the straight line stuff...What size boat and engine, what RPM are you reaching? and at what speed.

A higher engine will allow more bow lift, propped badly reduces maximum thrust, thrust is needed to raise the bow, dropping the engine increases drag which increases slip at speed, slip is why the bow will not raise at speed.

A good setup mess = adequate power, low engine and not reaching on or above manufacturers recommended RPM with a full load onboard...if you have one of the above you need to fix all of the others or you will go around in circles...possibly end up fitting a foil.

cheers fnq

Boat is a 4.4m fibreglass runabout with a 50hp Yamaha 2 stroke. Max RPM is 5500.


Hi Matt

Where was you cav plate sitting in relation to the water surface when that pic in post 22 was taken?

Knowing that will make it easier to suggest possible options.

Cheers
Chimo

I'm not sure, but I'll get a mate to have a drive tommorow so I can have a look.

Cheers :)

Matt.

[finga]

I'm not sure, but I'll get a mate to have a drive tommorow so I can have a look.

Cheers :)

Matt.
For goodness sake don't fall overboard. :oops:

[Chamelion]

For goodness sake don't fall overboard. :oops:

If I do fall overboard I might get a better look at it. :P