etec on allison

[pete8862]

Hi guys,

New to this site so i'm hoping to get some help on a problem with my \"Allison Fisherman 5\" got the boat 2nd. hand & fitted an Evinrude 75 Etec which runs perfect, but cavitates on turns, does anyone know someone that might fix this problem.

Pete

[Feral]

Tight turns or all turns?

If only tight turns it may be \"high siding\" enough for the cav plate to be leaving the water.

[AZZA]

Hi Pete welcome to the site like Feral said if the motor is set too high it will get to close to the surface and cavitate .Not sure on the hull of your boat but mine being pressed alli in tight turns the ribs on the hull cause air bubbles to travel under the hull into the prop causeing it to ventilate to over come this it is nessary to trim motor in as I turn and trim up as I come out of the turn.Quite easy with a bit of practice.

[Fisher_90]

Maybe post a pic of the transom with the motor fully lowered from behind and side on,

[Angus]

I am not a motor guy, but i agre with Fisher_90 comment, can we get a pic. Im sure youll get some great feed back then!

By the way welcome to the site!

Angus

[rumrunner]

my old boat did this!

try dropping the motor down 2\" from the transum! it will also plane out quicker! and prevent cavitation!

but if you can feel drag or unstable steering at high speeds put it back to where it was!

if you get your hands on a manual for that motor it will show how to mesure motor to transum for correct opperation!

mine is 22\" from bottom of transum to lowest facing point of engine brace(the bit underneeth the engine bracket where the transum hitts if the motor dropps down)

i have tried down and up positions to find the best drive and have found that 2\" below manufacturs recomendations is best for no cav!

hope this helps?

regards Ian

[rumrunner]

sorry i should add the cav plate should line up (the same leval) with a ruler or pencil when placed under transum and motor is at full down trim position!

[shortie]

The position of the motor will depend on what you want to use the boat for.

Skiing/ towing tube where high speed turns happen frequently. Lower the motor a notch at a time and test.

Straight line and slow speed turns where the cavplate is less likely to leave the water a higher motor position is better.

It will create less drag in the water. You will reach the correct rev range of the motor giving you the full 75 HP that you paid for. thus a better top spped and use less fuel.

What revs is the motor doing at flat out. This is an indication of also of how high low the motor should be placed on the transom.

Richard.

[faulked]

hi guys this is what i got taught many moons ago [img size=500]http://www.australianfishing.com.au/media/kunena/attachments/legacy/images/cav_plate_height_AFO_AFO.jpg

top pic for fishing bottom pic for race boats some place close to fishing works for me

[rumrunner]

you can drop it up to two inches below the first pic for drag racing and skiing!

great take off and no cav on ext hard turns!

Ian

[Fisher_90]

The general rule of thumb is cavitational plate lined up with the bottom of the hull

[Bommie]

If you have trim/tilt when cornering trim the nose right down, and when going straight trim the nose up as far as possible stop before the nose starts to porpoise up and down:)

(sorry Azza already mention this):S

[pete8862]

nearly all turns (sorry for taking so long to reply)

[pete8862]

i'll take some piccies

[pete8862]

some photos

[Fisher_90]

Ok u need to resize the photos to under 500x500pixels and 100kb

[Fisher_90]

O and a good bloke to take it to would be Alan Downes at Downes Marine in at bowen hills, Hes on Allison St and is a specialist johnson/evinrude dealer. He'll sort it out for you.

[pete8862]

thanks for that i'll try him

[pete8862]

Hi Ian,

Can you tell me if you have a pod or is your motor on the transom.

Peter

[Fisher_90]

Im pretty sure from seeing pics his is on the transom

[rumrunner]

pete8862 wrote:

Hi Ian,

Can you tell me if you have a pod or is your motor on the transom.

Peter

sorry Pete i wasn't following the thread!

yeah its on the transum!

Ian.