cavitation plate

simon23 · 23 February 2014, 19:24

Sorry I know it's been asked a hundred times before but is the cavitation plate level with the keel the best place to start when fitting a new outboard? Thanks in advance.

nugent · 23 February 2014, 19:39

Quote:

Originally Posted by simon23

Sorry I know it's been asked a hundred times before but is the cavitation plate level with the keel the best place to start when fitting a new outboard? Thanks in advance.

What boat?
Size of engine ?

simon23 · 23 February 2014, 20:24

6.1 mtr tohatsu one design rib
Mariner 125 hp 2 STROKE

Jizm · 23 February 2014, 20:29

Quote:

Originally Posted by simon23

6.1 mtr tohatsu one design rib Mariner 125 hp 2 STROKE

Got any pics?

Johnscubanut · 23 February 2014, 20:31

Always believed it should be within an inch or so level with keel?

nugent · 23 February 2014, 20:34

Cav plate set. 1 Inch above hull line,,,,,and 1 1/2,offset to the right

My osprey was set level with hull and was spraying as the attached

Lifted it up and runs much better

Johnscubanut · 23 February 2014, 20:38

I learn something new every day here! (well most days) Cheers!

simon23 · 23 February 2014, 20:52

Quote:

Originally Posted by Jizm

Got any pics?

Pics of what?
boat and engine are 20 miles apart at the moment

simon23 · 23 February 2014, 20:58

Thanks nugent. 1" above sounds good, although THe 1 1/2" offset is a bit more frightening !

Jizm · 23 February 2014, 21:17

Quote:

Originally Posted by simon23

Pics of what? boat and engine are 20 miles apart at the moment

Ahh. Not mounted yet then....

With that hull you may get away with going even higher.

simon23 · 23 February 2014, 21:39

Thanks
Not picking it up till Sunday. Guy I'm buying it off has a beam in his garage to hoist it up with, so I want to try and get it as close as possible first time

bosun · 26 February 2014, 19:38

I fitted an engine to a humber the other day where the actual cutout in the transom was offset, so you fit the engine in the middle of the cutout but its then actually offset to the keel.
Hopefully this was a clever bit of pre setup design not just dodgy build quality !

simon23 · 03 March 2014, 19:40

Bolted my new engine onto the rib yesterday set the cavitation plate 1 1/2" up from the keel. As with the Humber boson was working on the cutout is about 3" to the right. So fitted the engine in the center of it . the hole's lined up so it's a good place to start

9D280 · 06 March 2014, 09:14

If you drill the holes in the trransom so it's level with the keel and the bolts are in the top of the hole set on the engine you can then lift it if you get the "Bellagio effect".

Assume at that size it's power trim - winding it up with thwe PT might cure any "first guess" issues.

FWIW my cav plate is about 0.5" higher than the keel - my transom mount sounder module (allegedly also meant to be level wit hthe bottom of the hull) is actually higher than the bottom of the transom by about 1" - but it is also 1/2" back from it's design position as I glued a lump of wood to the transom to avoid drilling the transom itself.

The water moves up once the hull gets out the way so the further back you go the higher whatever is off the transom needs to be to "meet" the passing surface of the brine.

I;ll habvd you back to people with similar sized boats / engines

steco1958 · 06 March 2014, 11:03

I will probably sound thick now, why do you have to offset the engine, and WTF is the Bellagio effect ???

Bellagios, is a restaurant about 1 mile from my house, serves fantastic food !!

Solent Bombard · 06 March 2014, 11:20

Offsetting the outboard is a solution to prop torque steer from large engines and can also help to reduce chine walking I believe.

When I picked my boat up it had a massive pull to starboard on the wheel with anything from 1/4 throttle upwards but the engine had been put in the centre by the owner at the time.

So I'm hoping offsetting my engine to starboard by 1.5 inches will help to reduce the pull to starboard from the prop.

And If it does not help to reduce it dramatically I'll have to invest in a hydraulic steering setup.

steco1958 · 06 March 2014, 11:44

Quote:

Originally Posted by Solent Bombard

Offsetting the outboard is a solution to prop torque steer from large engines and can also help to reduce chine walking I believe.

When I picked my boat up it had a massive pull to starboard on the wheel with anything from 1/4 throttle upwards but the engine had been put in the centre by the owner at the time.

So I'm hoping offsetting my engine to starboard by 1.5 inches will help to reduce the pull to starboard from the prop.

And If it does not help to reduce it dramatically I'll have to invest in a hydraulic steering setup.

So it is similar to the pull on a front wheel drive car ??

Solent Bombard · 06 March 2014, 12:57

Yeah pretty much I suppose there may be others with more of knowledge than me to explain it better just in case I'm totally wrong