70hp on an Avon SR4?

[Alex r]

Sorry, by the way what would be the best price for my evinrude 70hp power tilt and trim? Thanks again alex

[matt h]

Post some pics etc. and a chassis plate,, that would help Alex

[Mextli]

Originally Posted by Alex r

What would be the optimum transom thickness required for a 50hp +engine, thanks alex

I'm running 30mm wood plus GRP on both sides.

Just went down to measure, the Transom is 40mm thick all in all. Makes it a bit stern heavier, but that's still manageable.

Mine has a different Deck-Transom construction than the original one though, my transom goes down all the way to the keel, and the deck has been put in afterwards, whilst Avon originally put in the deck first and then the transom(At least the sandwich part of it).
There are nails going through the deck into the transom which is one of the reasons why the transoms on SR4s tend to be slightly wet.

[Alex r]

Just popped downn a measued the transom It - 47mm thick +10mm plywood on the outside plus at the top the fiberglass is flush on the inside with a lip of about 3mm, total thickness approximately 57mm, hope this helps.
By the way the engine is a evinrude 70hp 2 stroke long shaft (1981) , with power tilt and trim and remote throttle, cable operated steering, many thanks alex

[Mextli]

Okay, then someone already reinforced the transom.

The usual SR4(the one with metal transom braces) transom should be fibreglass outside as well as inside with a metal strip screwed on top to prevent water ingress(which it never does properly)

If someone has reinforced your transom by screwing/nailing plywood or sheet metal to the outside - Check the screws/nails for being watertight. that was one thing that killed mine and a friends transom - both SR4s that were being run by the german equivalent of the RNLI, both had heavily "reinforced" transoms, and the wood within the GRP had turned to compost, compromising the stability of the whole boat.

If, of course, your boat is a "deluxe" SR4 without the metal transom braces but with the "moulded" deck and the GRP transom braces, then the above might not be appliable, as I have never taken apart one before.

If your engine is in good condition and has PTT it should fetch a nice price. At least over here in Germany it would.

[Alex r]

Just so I have it clear mine is fiberglass on the inside going straight over the top and down about 40mm then goes in about 3mm then fiberglass straight down, where the engine mounts there is a plywood panel (chamfered edges) fixed to the transom, 47mm fiberglass to fiberglass +10mm plywood, giving total of about 57mm (ish), does that sound about right, many thanks alex

[beerbelly]

a picture would be better Alex heres pics of my old one

[matt h]

That mercury is the very best engine for a sr4. Weighs 80kgs ish... . dont alter the transom.. find the right engine

[Alex r]

Photos of my rib, any help? Thanks alex

[matt h]

Deluxe version. Leave the transom alone and looks for a merc 40-50 two stroke .
Also shift the fuel tank under seat for better weight distribution.
(40 two stroke up to 2006)
(50 two stroke up to 1999) im sure after that they got heavier
Yam 40 two stroke or 4stroke.
Yam 50 two stroke also good but a heavier 3 pot engine.

No more than 100kgs max as it wont go any faster than 39 knots withoit chucking you out. A correctly balanced sr4 will do 37 with a twin pot merc ..

[beerbelly]

No more than 100kgs max as it wont go any faster than 39 knots withoit chucking you out. A correctly balanced sr4 will do 37 with a twin pot merc ..[/QUOTE]

that's what mine did 36-37 knots but was nice and stable at that even when the sea conditions were suggesting I slowed down I had one 25 litre tank and battery under the jockey seat and another 25 litre tank in front of the console, was a cracking little rib and I'm sure ill regret selling it

[Nos4r2]

Originally Posted by matt h

Deluxe version. Leave the transom alone and looks for a merc 40-50 two stroke .
Also shift the fuel tank under seat for better weight distribution.
(40 two stroke up to 2006)
(50 two stroke up to 1999) im sure after that they got heavier
Yam 40 two stroke or 4stroke.
Yam 50 two stroke also good but a heavier 3 pot engine.

No more than 100kgs max as it wont go any faster than 39 knots withoit chucking you out. A correctly balanced sr4 will do 37 with a twin pot merc ..

After seeing Gibbo's SR4 with the big propped Yam 50 2 stroke launch itself out of the water, I'd suggest that a Merc/Mariner Bigfoot 2 stroke or a late (well, as late as is possible) model Yam 50 2 stroke would be about as much fun as you can have with an SR4. Mine had a (93ish) merc 3 pot 50hp on it with a normal 10.5" diameter prop and was nuts. The extra grip from Gibbo's bigger prop made for jetski-like acceleration.

As you say, at 39 knots they get so flighty and chinewalk so much that you really don't want to be trying to go any faster anyway.

[tom_20000]

Shameless plug but I have a 50hp M50D2 2006 model thats for sale. Details are in the bits and bobs for sale section on here. Currently mounted on my SR4, very light weight and very quick

[mwb.wright]

Originally Posted by beerbelly

that's what mine did 36-37 knots but was nice and stable at that even when the sea conditions were suggesting I slowed down I had one 25 litre tank and battery under the jockey seat and another 25 litre tank in front of the console, was a cracking little rib and I'm sure ill regret selling it

The new owner loves it so he doesn't regret a thing :-)

[Mextli]

Anything over 25kts in rought weather will be highly uncomfortable anyway. Acceleration is what you need.

@Alexr, as someone already said you have a Searider with a "moulded" deck, the deluxe version!

Engine wise, the three - cylinder Yamahas are very good especially with PTT.

Personally, I swear on the two-cylinder 55 Yam, it has more torque than the 3-pots, at about the same weight. Unfortunately you'll need to pre-mix the oil and it doesn't have PTT.
And it uses more fuel. And it's got a slightly dodgy idle.

[Alex r]

Thanks for all your help and advice guys, what I've learned is i will soon be on the lookout for an 50hp merc or yam 2 stroke engine, but i will take the rib out with the 70hp on the back - very very carefully - any problems and she will be straight back ashore till i get the 50hp, i will make some of the weight adjustments advised, any other advice would be greatly appreciated, many thanks alex

[Alex r]

Just a quick update (forgot to put in the last post!) just seen a 50hp yam for sale, just wondering is there much of a call for 70hp outboards, don't see many advertised? Thanks again alex

[A1an]

Originally Posted by Alex r

Just a quick update (forgot to put in the last post!) just seen a 50hp yam for sale, just wondering is there much of a call for 70hp outboards, don't see many advertised? Thanks again alex

to be honest that outboard is not very sought after and itl require a good sales pitch to get rid of it but anything will sell if its cheap enough, I wouldn't factor in the sale price into your budget for its replacement.

[Chris Caton]

My SR4 has a Honda 50 fitted, 34k is fast enough for a fat old man like me, it's fitted with a console/twin jockey seats and a 90l fuel tank, still sips the fuel and goes well enough, still got the flooding hull