Mounting engine 4" off transom? (Atlantic 21 / Yamaha 200)

alt · 15 August 2020, 15:36

Hi all,
Friend is re-furbishing an Atlantic 21. He has a Yamaha 200 2-stroke to go with it (Direct Injection).

The issue is that it's an XL Shaft.

The only way he can get the cavitation plate to line up with the hull is to have the engine mounted approx 4" off the transom (even at this, he's going to have to drill new mount holes in the engine).

Is this too high for such a big / heavy engine?

Also, at this, the top mount bolts will be only approx 1" below the top of the transom.

Thoughts?!

beerbelly · 15 August 2020, 16:32

i have a pair of jack plates same as these surplus to requirements:
eBay item number:264388604455

alt · 15 August 2020, 16:41

Quote:

Originally Posted by beerbelly

i have a pair of jack plates same as these surplus to requirements:
eBay item number:264388604455

Can you pm me a price? Inc postage to irelanf

phantom 19 · 16 August 2020, 09:35

No, Will be fine, rigged an F300 on a CMC powerlift on an Atlantic 75 some years ago. A frame needed raising six inches to prevent cowling hitting it when tilted

whiskylee · 16 August 2020, 12:43

I've got a Hydraulic outboard power lift in my garage if your friend wants a second hand lifter

Quote:

Originally Posted by alt

Hi all,
Friend is re-furbishing an Atlantic 21. He has a Yamaha 200 2-stroke to go with it (Direct Injection).

The issue is that it's an XL Shaft.

The only way he can get the cavitation plate to line up with the hull is to have the engine mounted approx 4" off the transom (even at this, he's going to have to drill new mount holes in the engine).

Is this too high for such a big / heavy engine?

Also, at this, the top mount bolts will be only approx 1" below the top of the transom.

Thoughts?!

beerbelly · 16 August 2020, 16:01

pm sent

alt · 18 August 2020, 21:47

Thanks for the help so far - Think I have a jackplate sorted thanks to the forum.

I know this is a bit of a wildcard question... a 200HP on an Atlantic 21... how would you mount the cavitation plate relative to the keel? level? higher? lower?

beamishken · 18 August 2020, 22:42

Quote:

Originally Posted by alt

Thanks for the help so far - Think I have a jackplate sorted thanks to the forum.

I know this is a bit of a wildcard question... a 200HP on an Atlantic 21... how would you mount the cavitation plate relative to the keel? level? higher? lower?

I'd start testing an inch above level but have some adjustment either way

alt · 21 August 2020, 15:56

We are ordering a static jack plate, so we'll try .5" above level and see how we go.

beamishken · 21 August 2020, 18:08

Quote:

Originally Posted by alt

We are ordering a static jack plate, so we'll try .5" above level and see how we go.

Your jack plate probably has a 100mm or so of setback which means you can go higher if you want to maximize performance
The further the setback the higher the engine can go
But its all trail and error to get the sweet spot, dont be frightened to move it up or down until your happy

alt · 22 August 2020, 00:13

Quote:

Originally Posted by beamishken

Your jack plate probably has a 100mm or so of setback which means you can go higher if you want to maximize performance
The further the setback the higher the engine can go
But its all trail and error to get the sweet spot, dont be frightened to move it up or down until your happy

Many thanks.

I'll try to configure it with the jackplate mounted that the highest hole on the 2 top screw-hole mounts of the engine is 1" above the transom... it can then be easily lowered 1 screw hole at a time until a sweet spot is found.

I know the jackplate will probably come with instructions but regards mounting... do you fix the jackplate to the engine first and then mount the jack-plate to the transom?

Below is a pic of what i've purchased off a forumite for reference, it's 2 separate plates.

alt · 22 August 2020, 00:17

Just to add, there are currently no holes in the transom. This is an Atlantic 21 which is now being fitted with a single Yamaha 200HP 2Stroke. Holes from previous twin installation have been filled in.

diver 1 · 22 August 2020, 06:18

Sorry to jump in but are those angle brackets stainless or aluminium out of curiosity? I'm asking because I might need to do something similar soon, fitting an XL engine on a L transom. I was thinking about extending the transom height and reinforcing it with something like you have there.

beamishken · 22 August 2020, 07:53

Thats different to the jack plate I've seen in the past & doesnt give the same ease of adjustment or the set back I'd expected
Others I've seen comprised of two sets of u channels 1 bolted to the engine the other to the boat with slots & vernier adjustment to fine tune the height similar to this one
https://www.ebay.com/itm/290787292381

beerbelly · 22 August 2020, 09:55

Quote:

Originally Posted by diver 1

Sorry to jump in but are those angle brackets stainless or aluminium out of curiosity? I'm asking because I might need to do something similar soon, fitting an XL engine on a L transom. I was thinking about extending the transom height and reinforcing it with something like you have there.

there aluminum