Raising outboard higher

[SirFaffer]

Hi all, have a 4.21m tinny with a 30hp etec on the back at on the tallest bolt holes I'm still dragging the anti cav plate through water, which is suggesting drag. My top speed is suffering and im topping out at 38kph with two people and all of our gear.

Am trying to decide between having my transom extended or running a riser/jack plate, so was wondering if any of the following would be suitable.

Mercury 9-9 -50 Hp. Outboard Engine Transom Install Bracket

Ideal for trade marine mechanics and dealerships and designed to offer more flexibility for transom heights for sort and long shaft enginesThese are called Clearwater brackets in the states but this model boastsI tested of wood rubber antibtation panel 230 Mm x 260 Mm 40 Mm thick,This unit is...

ozmarine.com.au

4

To suit tinnies inflatables and small dinghy's rated 6-30 HP. The adjustment aft is 5-7 inch back from the transom. Height is adjustable on the engine plate 2 inches. Includes 3 sets of transom holes you can raise the engine another 4 inches if need be. Nylon slotted engine board included. Made...

ozmarine.com.au

Clearwater Transom Bracket

*Suits 9.9-50hp Motors.*100mm Setback*260mm Height 420mm Width*8 hole positions to suit all transom styles*50mm Tick rubber anti vibration pad supplied*Weight - 14LB

ozmarine.com.au

Jack Plate JPL4000 Adustable Outboard Boat Jack Plate | eBay

This Jack Plate is designed for smaller motors to improve the performance of your boat. Two pairs of precision machined aluminum angles locate the motor with 6" setback from the transom. Stainless steel bolts hold the angles in place.

www.ebay.com.au

Also toying with the idea of going a lower pitch prop as I'm only hitting 5400rpm, but accept that maybe that'll change with the outboard up a bit higher?

Cheers

 

[airshot]

When a straight edge is pushed up against the bottom of your hull, and the motor is tilted so the cav plate is parallel to the straight edge.....how high or low to the hull bottom is the cav plate ?? This should be your initial starting point. If cav plate is level with hull bottom, moving it up or down won't do much without customizing your prop. Adjust your prop pitch so your motor reaches max rpm with just you and basic equipment on board. If you choose to make changes to the motors height, the jack plate is the best way to go, other than the cost !! Also be sure your motor is running at top performance, or you will be starting over with your setup.

 

[Chris1956]

Gee, can you put a 2X2 between the motor and transom to raise it up a bit?

 

[jimmbo]

Gee, can you put a 2X2 between the motor and transom to raise it up a bit?

If it is Bolted to the Transom, there is no Need for any spacer. If it is just fastened with the Clamp Screws, you have to be careful as to how high you go. Too high and the Engine will be at increased Risk of coming off the Transom, due to lack of Clamping Area
By chance are you trying to install a long shaft(20") motor on a 15" Transom, or an extra long shaft(25") motor on a 20" Transom?

Some Pics, from the Side, and Rear, taken Level, down at the Height of the Hull Bottom, which the Motor Positioned like mentioned in Post #2, will give us a better insight...

 

[SirFaffer]

When a straight edge is pushed up against the bottom of your hull, and the motor is tilted so the cav plate is parallel to the straight edge.....how high or low to the hull bottom is the cav plate ?? This should be your initial starting point. If cav plate is level with hull bottom, moving it up or down won't do much without customizing your prop. Adjust your prop pitch so your motor reaches max rpm with just you and basic equipment on board. If you choose to make changes to the motors height, the jack plate is the best way to go, other than the cost !! Also be sure your motor is running at top performance, or you will be starting over with your setup.

Yeah it's not quite level.

Gee, can you put a 2X2 between the motor and transom to raise it up a bit?

It's bolted on.

If it is Bolted to the Transom, there is no Need for any spacer. If it is just fastened with the Clamp Screws, you have to be careful as to how high you go. Too high and the Engine will be at increased Risk of coming off the Transom, due to lack of Clamping Area
By chance are you trying to install a long shaft(20") motor on a 15" Transom, or an extra long shaft(25") motor on a 20" Transom?

Some Pics, from the Side, and Rear, taken Level, down at the Height of the Hull Bottom, which the Motor Positioned like mentioned in Post #2, will give us a better insight...

I'll grab pics tomorrow. Long shaft hull, 20" leg.

 

[jimmbo]

One Caveat regarding placing the AV Plate even/level with the Hull Bottom. This an Aluminium Hull, if it has a Protruding Keel, that will require the Motor be lower than on, a Fiberglass Hull, which usually don't have a protruding Keel

 

[Captain Caveman]

Many years ago I had a long shaft '79 Evinrude on a mid-80s Fisher boat. The plate was a few inches below the hull. Since it was a clamp on, I really couldn't really go higher as jimmbo noted. However, I bought a piece of 2x2 aluminum tube along with two scraps of flat aluminum, had my buddy weld them together, and bolted my lift to the transom. It definitely made a difference in how that motor performed.

If I would have had the money though, a jackplate would have been the smarter move.

 

[airshot]

Yeah it's not quite level.

It's bolted on.

I'll grab pics tomorrow. Long shaft hull, 20" leg.

What do you mean, not quite level ?? You adjust the motor trim until it is parellel to the bottom. This is just a starting point....is cav plate even, above or below the hull ?