Longshaft or shortshaft , Avon SR4 ?

nousername · 17 June 2020, 21:51

I have an old sea rider 4m Rib. She is in the middle of a refurb and part of the refurb will be a bigger HP engine.
She currently has a longshaft 40 hp yamaha engine. The engine is bolted through the transom and is raised around 2" above the top of that...
I would like a 50-60 hp 2 stroke engine but would like that engine to sit on the transom perfectly and not sitting above it to make the prop sit rcorrectly in the water....
What engine shaft size goes with one of these small ribs ? Maybe in inches rather than the usual terminology

beerbelly · 18 June 2020, 05:51

20 inch long shaft required for an Avon sr4

beamishken · 18 June 2020, 06:51

If the current engine is raised it was probably done to increase performance, with a reasonably fast boat raising the engine so the av plate is slightly above the bottom of the hull usually gives better speed. You will need to experiment with your new engine but you may find it performs better being 25-50mm high. Assuming your current set up works ok you may find that the engine is at the optimum height

Nos4r2 · 18 June 2020, 08:16

If the transom is flat across the top, 20" shaft.

If someone's buggered about with it (IE it's not flat across the top-a few have been, to fit the ex RNLI mid shaft 40 or a short shaft) then post pics.

Hell, post pics anyway

nousername · 13 September 2020, 10:40

Ok, Thanks for the replies and advice. Problem was boat was at my uncles house and i couldn't get access to it because of covid.
Turned out the engine on it had a 23" shaft. I found a nice yamaha longshaft (20"), 50hp which has now been fitted and sits perfect.

nousername · 13 September 2020, 10:43

Quote:

Originally Posted by Nos4r2

Hell, post pics anyway

How do you post pictures Btw ? I used to use photobucket but that platform went to the dogs a few years back.

Livid · 13 September 2020, 21:33

in the advanced reply section you can add attachments, I do love a good searider, are you keeping the engine stock? you're a lucky guy for getting your mitts on a 2s 50hp yamaha, they're as common as rocking horse excrement

Ferryman · 13 September 2020, 21:45

Quote:

Originally Posted by Livid

in the advanced reply section you can add attachments, I do love a good searider, are you keeping the engine stock? you're a lucky guy for getting your mitts on a 2s 50hp yamaha, they're as common as rocking horse excrement

I scrapped one a few years ago because I’m an idiot!!

Livid · 13 September 2020, 21:58

Quote:

Originally Posted by Ferryman

I scrapped one a few years ago because I’m an idiot!!

as screwups go that's pretty big haha, could have sold that for a pretty penny even if it was buggered

nousername · 14 September 2020, 08:48

Quote:

Originally Posted by Livid

in the advanced reply section you can add attachments, I do love a good searider, are you keeping the engine stock? you're a lucky guy for getting your mitts on a 2s 50hp yamaha, they're as common as rocking horse excrement

I will most likely leave as is. I got 38mph with 2 adults, a car battery, gear and a 18kg aux engine. Felt planted but after doing some research i believe that to be a sweet spot with the sr4.
It was the old delux model i had, no room to swing a mouse so i stripped it bare, built a centre console and cut up what was left to make a centre jockey and 2 rear seats next to the engine.
Bought 2 tins of paint for the outside and they weren't quite enough to finish the job, at £60 a tin i chose to call it a day with that though.
Can fish of it quite comfortably now! , Thanks for the photo advice

Livid · 14 September 2020, 18:01

Quote:

Originally Posted by nousername

I will most likely leave as is. I got 38mph with 2 adults, a car battery, gear and a 18kg aux engine. Felt planted but after doing some research i believe that to be a sweet spot with the sr4.
It was the old delux model i had, no room to swing a mouse so i stripped it bare, built a centre console and cut up what was left to make a centre jockey and 2 rear seats next to the engine.
Bought 2 tins of paint for the outside and they weren't quite enough to finish the job, at £60 a tin i chose to call it a day with that though.
Can fish of it quite comfortably now! , Thanks for the photo advice

I'm keeping mine deluxe, I don't need any practicality and love the dynamics with all the weight up front and the windscreen keeping all the spray off. My Yamaha 40 is boring me so I'm boosting it a lot so it should be great fun

Poly · 14 September 2020, 18:12

Quote:

Originally Posted by nousername

How do you post pictures Btw ? I used to use photobucket but that platform went to the dogs a few years back.

If you are in the app its fairly self explanatory.
If you are in a browser - click the paperclip icon, then you should get a new window to "manage attachments" and you add them THEN click upload