Prop ideas for SR5.4 & yam 90?

pail rider · 22 October 2013, 07:09

I recently acquired a 2002 SR5.4 with a 2002 yamaha 90hp 2-stroke on the back.

The aluminium 15 x 17 prop has a few nicks on it so I'm thinking of getting it refurbed but before I do I was wondering if it is actually the best suited prop for my set up or whether I should go for a new prop of a different size?

Has anyone got experience of my rib/engine combination? I'd appreciate any advice people might have.

Should probably mention I have a blocked hull.

RIB-Teccie · 22 October 2013, 19:27

Hello

Usually yam props for that engine were (from memory) 13.5" x 13, 15, 17, 19 or 21". If you are loading the rib with fuel, crew & kit, you would look at the 15 pitch. The 17 would be a good utility choice.

As you have a damaged prop, you won't know the current RPM, which is a pain. A standard yam alloy or the black stainless is a good choice. I have seen a lot of premature shock absorber (rubber) bush failure in other makes.

It always boils down to what you are doing, but you are looking to be at 5000-5500 rpm at full throttle. Unless you are really picky, finding a prop that tops out at 5300 is a good compromise when fully laden, then you will get the extra rpm when lighter.

matt h · 22 October 2013, 21:22

i always use 13/1/4 by 19 pitch all which gave me 39 knots . one person, heavy consol and 30 litres of fuel

sparky666 · 22 October 2013, 23:15

I ran my dory eurosport on a 19p with a 90 no problems and for one up cruises I had a 21 p 5800rpm over 40 it flew

Nos4r2 · 23 October 2013, 01:59

You won't swing a bigger prop than a 19" on a Yam 90/SR5.4.

pail rider · 23 October 2013, 09:16

Thanks all. Kind of confirms my thinking that a new prop is a good idea. I'll keep the other as a spare.

Anyone know a good prop supplier in/near Bristol?

A1an · 23 October 2013, 12:05

Steel Development can refurb your prop for you.

Google is your friend.

pail rider · 23 October 2013, 18:20

Quote:

Originally Posted by A1an

Steel Development can refurb your prop for you. Google is your friend.

Thanks A1an

Took another look at the prop this evening it has 13X19 K written on it.

So think I'll get it refurbed then see what rpm that gives me at WOT before deciding if I need anything different.

C-NUMB · 23 October 2013, 19:04

13X19 K has been best choice so far om mine 5.4 /90. Defo not a 19 black max....
Will test a 17 ballistic next weekend weather permitting. Will report outcome.

Bushrider · 23 October 2013, 19:23

Quote:

Originally Posted by C-NUMB

Will test a 17 ballistic next weekend weather permitting. Will report outcome.

I tried a 17" Ballistic on my 5.4 with a 90 Yamaha but was not very impressed by the performance .
I changed back to an 17" Yamaha K series prop which worked for me best on the SR .
The Ballistic is now on my Buster XL with F100 where it performs excellent !
Perfect whole shot , rev´s with 6000rpm , 4 persons on board & tube or waterski no problems.

RIB-Teccie · 23 October 2013, 19:37

What WOT RPM did you get with the 17k ??

Bushrider · 23 October 2013, 19:51

Quote:

Originally Posted by RIB-Teccie

What WOT RPM did you get with the 17k ??

Really can´t remember .. these tests are a year ago and the SR is sold now ..
sorry ..

C-NUMB · 23 October 2013, 21:11

Quote:

Originally Posted by Bushrider

I tried a 17" Ballistic on my 5.4 with a 90 Yamaha but was not very impressed by the performance .
I changed back to an 17" Yamaha K series prop which worked for me best on the SR .
The Ballistic is now on my Buster XL with F100 where it performs excellent !
Perfect whole shot , rev´s with 6000rpm , 4 persons on board & tube or waterski no problems.

Yes prop testing is black art...You never know what will happens...will test i anyway.

You sold the SR, are you serious

?

Nos4r2 · 23 October 2013, 21:49

Bear in mind the max recommended operating rpm for a Yam 90 2 stroke is 5500 rpm. I hit 5500 RPM with a 17k on the 85 Yam/SR5.4 (same motor bar premix)

Dan Gurney · 24 October 2013, 00:02

Quote:

Originally Posted by Nos4r2

Bear in mind the max recommended operating rpm for a Yam 90 2 stroke is 5500 rpm. I hit 5500 RPM with a 17k on the 85 Yam/SR5.4 (same motor bar premix)

Same motor on my Attaque 5.3 also tops out at 5500 with 13x17. Cruising speed is better than the 15 it came with (though obviously you lose a little holeshot). Will be interested to see next season how changing the height affects thing. 34 knots is current WOT on flat non-tidal water.

Kat1nka · 24 October 2013, 07:54

Quote:

Originally Posted by Nos4r2

Bear in mind the max recommended operating rpm for a Yam 90 2 stroke is 5500 rpm. I hit 5500 RPM with a 17k on the 85 Yam/SR5.4 (same motor bar premix)

Does anybody know where the RPM-limiter comes into play on a Yamaha 90 ? Some people say 6000, others 5800 rpm.
One ex. racer told me that you should aim for 5800 rpm for the 90 AETO.

My top rpm at WOT so far is 5700. The prop was a Solas Titan SS 13 1/4 x 17 and the rib is an SR 4.7. Topspeed 40,5 knots. The Avon does 42 - 43 knots with the 12 5/8 x 21 alu at 5200 - 5300 rpm so the search goes on.

Still testing for the perfekt prop...

RIB-Teccie · 24 October 2013, 19:05

I always thought it was. 6000 RPM, but I will try to find out.

If you are operating above 5500RPM, you are just burning fuel, unless you have had the engine race prepared to pump out over 110 HP, then you will be revving harder. It's unlikely most on here will blow a Yammy rev limiter but you will know when you have, the rev limiter comes on at 2000RPM in idle and going ahead at all but min RPM is impossible, accompanied by a very strange misfire. On the older engines with the wired CDI it was an easy fix as you would disconnect the wire and tape up the connector. It was always disconnected on a race engine.

At Mitsui in the late 1970s early 1890s they experimented with NOX and the carbs froze, the 85hp yam hit well over 10000rpm and was only stopped by pulling the fuel line as it became a compression firing engine at that speed. After it was stripped, there was no damage discovered.

Dan Gurney · 24 October 2013, 20:35

For what it's worth the spec sheet I found for my 85AET the "max rev range" is 4500-5500.

RIB-Teccie · 24 October 2013, 21:05

The 4500 lower end was for use with displacement craft, such a barges or houseboats but I've never seen one. This was because a hole shot was not required but a higher thrust was. Some of the prop diameters changed for displacement or deep very hulls.

Nos4r2 · 24 October 2013, 21:52

Quote:

Originally Posted by RIB-Teccie

The 4500 lower end was for use with displacement craft, such a barges or houseboats but I've never seen one. This was because a hole shot was not required but a higher thrust was. Some of the prop diameters changed for displacement or deep very hulls.

Yeah, still not a good idea to prop one so it runs over 5500 rpm though.