Ribcraft 4.8 Yam 90 2stroke prop

[rockyrib]

Hi
I was wondering if anyone might be able to help me.

I recently bought a stunning ribcraft 4.8, it came with an etec 75 (which I had to sell sadly)

I have put my 2000ish yam 90 2 stroke outboard on it.

I was wondering if anyone had a good idea of what prop should be on it, at the moment I have a very chewed up ally one and looking to replace with a stainless one as a christmas present to myself.

Many thanks

Tim

[Downhilldai]

Yam 90 on a Ribcraft 4.8?

[gibbo500]

Originally Posted by rockyrib

Hi
I was wondering if anyone might be able to help me.

I recently bought a stunning ribcraft 4.8, it came with an etec 75 (which I had to sell sadly)

I have put my 2000ish yam 90 2 stroke outboard on it.

I was wondering if anyone had a good idea of what prop should be on it, at the moment I have a very chewed up ally one and looking to replace with a stainless one as a christmas present to myself.

Many thanks

Tim

Chrikey a 90 on a 4.8?????

[gibbo500]

Originally Posted by Downhilldai

Yam 90 on a Ribcraft 4.8?

You beat me to it.

[rockyrib]

Hmm
Yep its rather tasty, I got 42mph on the gps with a wrecked prop (its a trade up from my avon 3.45 with a yam 40)

[matt h]

, blimey, well, over the power rating ..anyway as the engine weighs only 120 kg which is well under the Max weight , try a 13 x 19 ally lets see some pics of her

[outboardtech]

rockyrib if I were you I put put a higher pitch prop on that set up . you dont want too over rev that outboard man and blow the powerhead up . I have seen a 5metre with the same engine and the guy was running a 17 and was reving @ 5800 on W.O.T and the poor powerhead lasted 6 hours . he the customer was so happy as he was getting those revs but didnt really know what he was about to come across . YES a piston thru the block . So my advice and experience would be higher pitch too drop the revs . baz

[Jacob555]

My Novamarine 4.5 metre runs a Yamaha 60 2 stroke. I was reaching a screaming 5900 at WOT on a 15 inch prop so quickly upgraded prop to a 21 inch and its perfect now, topping out at 4950 at 5mph faster. This is a very light boat though. 190kgs ex engine! People with larger ribs think I am very odd running a 21 inch prop with only 60 hp, but its a great setup.

The place I got my prop from on ebay had another Yamaha 23 incher. In fact they have been relisting it for months. The number of customers who need to run a prop of such big pitch on an engine so small (15 spline 4.25 inch gearcase) is probably limited. The item is at http://cgi.ebay.co.uk/propellor-prop...item2ea68336df

I'm not garanteeing it will be right but its easier to work down pitches than up as there's less risk of blowing the powerhead up.

[rockyrib]

Hi Guys,
Thanks for all the help, I have decided to buy an ally prop first just to give it a go and see wether the one I buy is right before going for the stainless baby.

I have bought the one on ebay - £60 seemed dead cheap and I had a few quid in my paypal balance.

This may sound really stupid but can anyone just point out what the numbers mean I guess the pitch is the angle of the blades and the other measurement is the diameter?

So the one I got : 12 5/8 x 23
I guess the 12 5/8's is the pitch and the 23 the size of the blades?

Sorry for sound stupid

Tim

[chewy]

Originally Posted by rockyrib

Hi Guys,
Thanks for all the help, I have decided to buy an ally prop first just to give it a go and see wether the one I buy is right before going for the stainless baby.

I have bought the one on ebay - £60 seemed dead cheap and I had a few quid in my paypal balance.

This may sound really stupid but can anyone just point out what the numbers mean I guess the pitch is the angle of the blades and the other measurement is the diameter?

So the one I got : 12 5/8 x 23
I guess the 12 5/8's is the pitch and the 23 the size of the blades?

Sorry for sound stupid

Tim

12 5/8" will be the diameter and 23" the pitch, ie how much one revolution of the prop will move you forward in the water without any slip.

[rockyrib]

Fast response!

Thanks

[Downhilldai]

Why did you have to off load the e-tec?

[rockyrib]

I couldn't afford to buy the boat and engine outright, could only afford to get it if I sold the engine straight away (the etec was 1 year old and I had a 90 yam already)

[Downhilldai]

Are you aware of the max hp rating on a RC4.8?

Maybe selling the Yam and keeping the e-tec would have been a better option?

[rockyrib]

AFAIK its rated for a 60, I would have loved to keep the etec, 1 year old, still 2 years warrantee, unfortunately could not.

[Downhilldai]

Ok cool - as long as you know you're 50% over the rated max.

[rockyrib]

Hi again,
Know this was a long wait but here is a pic of my ribcraft 4.8 with the yamaha 90 that I asked advice about.

Planning to go out along for the first time this afternoon (tide out and launching is in mud with a zafira, need it to be a bit higher) and see how it does all set up!

Anyone clever know what I should be getting speed wise?

The yamaha multi function has given up the ghost - hence the tiny tach on the lid of the engine

[Rogue Wave]

I'm not clever just opinionated!

Thats a very good combination the second best sub 5 metre rib ever made and the finest 90 ever made. If your making the right revs at WOT then you should be seeing 40 knots mybe 45 plus.

We used to get 42 (very exiting) out of a 4.7 searider with a Yam 70 but I learnt a lot about Chine walking in the process!

[rockyrib]

Well I'm back and in one piece!

No kids to get too cold, no wife to say too fast, so had a lovely blast around exmouth and out into the bay

Still feeling my way with the boat, with the 23 prop on it i get 38.8 knots revving at 4800 but it cruises perfectly at 30 knots doing about 3000 revs.

I love boating!

[Mollers]

My Sis lives in Dawlish, she's been nagging me to take the rig up. We'll have to have a 30knt tear about around the Exe.