propping a yam 60 4 stroke / 5mtr humber

woot · 21 February 2005, 18:42

I know propping has been discussed many times and I have been reading lots of old posts. My 5m humber Assault with 60 hp Yam 4 stroke seems to be set up well with the ally prop supplied ( 11 1/8 x 13 - G ). Acceleration is good and when cruising and trimmed up I get very close to using the max rev range ( upto 5800 out of 6000 ). I don't yet have a fixed GPS so don't have any accurate speeds to quote. I intend to do some waterskiing using the boat next year. My dilemma is that I dont mind spending on a stainless prop if it will give me a significant improvement but I don't want to upset the good performance balance I seem to have at the moment and don't want to fanny about moving the engine up if I will gain very little. After researching the old posts I think I would be looking to fit a prop closely matched to the ally one and look for the change in performance based mainly on the change of material
Has anyone any advice or experience on what performance gain I am likely to get on my size of outfit particularly with regard to the skiing ( this is the only time I wish I had a bit more oomph ). I have tried to contact steel developments but couldn't get through on the phone this weekend.

arn.george · 21 February 2005, 19:03

Would be very interested to hear what speed you are achieving - looking at upgrading from Yam 40hp 4 stroke to 60Hp 4 stroke - have achieved 30 knots on Humber ocean pro 5m.
I gather the new 4 strokes with fuel injection are more powerful.

Bilge Rat · 21 February 2005, 19:03

Hi Woot

My engines proped exactly the same as yours and i've asked myself exactly the same question, sounds like we have simular set ups and power to weight ratio, mine also runs at about 5800 on a calm day.
I'm no expert on props but i believe if you raise the pitch you will drop the revs but gain a slight improvement in top end speed, however you will lose bottom end hole shot, and as this must be important when pulling a skiier i'd think it was unadvisable to go up in pitch, for this reason ski boats seem to run small props which are fast on take off and reach there top revs quicker.

Talk with Julie at Steel devs, she will put you on the right track and when you get the answers let me know

Bilge Rat · 21 February 2005, 19:08

Quote:

Originally Posted by arn.george

Would be very interested to hear what speed you are achieving - looking at upgrading from Yam 40hp 4 stroke to 60Hp 4 stroke - have achieved 30 knots on Humber ocean pro 5m.
I gather the new 4 strokes with fuel injection are more powerful.

Hi Arn
I'm achieving 33-35 knots depending on the weather conditions, fuel load and amount of people on board, two up and full of fuel it will run all day at 30 knots without missing a beat.
If i had the extra money i'd have gone for the high thrust gear box, the extra £200 was the straw that broke the camels back, i've been told they are dogs danglies on the new yams as you maintain power through the entire rev range.

arn.george · 21 February 2005, 19:10

Time to make enquiries

Far too tempted!!

Anyone offering on a 40hp four stroke fully serviced 130hrs in good condition?

woot · 24 February 2005, 17:38

Spoke to Julie at Steel Developments, after a chat she recommended that I leave the pitch, diameter etc the same as my ally but in the "New Saturn" stainless steel model. We hope that the improved blade shape and blade area of the stainless version will give better performance both off the mark and on top end. I think I'm going to bite the bullet and go for it, it will probably take me ages to get around to putting it on and trialling but when I do I'll post the results.

Bilge Rat · 24 February 2005, 21:12

Quote:

Originally Posted by woot

Spoke to Julie at Steel Developments, after a chat she recommended that I leave the pitch, diameter etc the same as my ally but in the "New Saturn" stainless steel model. We hope that the improved blade shape and blade area of the stainless version will give better performance both off the mark and on top end. I think I'm going to bite the bullet and go for it, it will probably take me ages to get around to putting it on and trialling but when I do I'll post the results.

Woot... Yes am very interested to hear your results gains and what differance to handling characteristics the stainless makes at the same pitch.

woot · 25 February 2005, 20:09

Bit the bullet lunchtime today and ordered from Steel Developments ( prop in stock ). Got a phone call from Julie later to tell me that a recon prop had come to her attention which was the exact model I had ordered which I could have for half price. Now thats what I call service, someone making a phone call to save me wad a few hours after I had just authorised them to spend double the amount. Apparently the recon has had very little use and should just need checking out and a buff up. All of a sudden it doesn't seem like such a big gamble to see what the SS prop will do for me.

Bilge Rat · 26 February 2005, 01:05

Quote:

Originally Posted by woot

Bit the bullet lunchtime today and ordered from Steel Developments ( prop in stock ). Got a phone call from Julie later to tell me that a recon prop had come to her attention which was the exact model I had ordered which I could have for half price. Now thats what I call service, someone making a phone call to save me wad a few hours after I had just authorised them to spend double the amount. Apparently the recon has had very little use and should just need checking out and a buff up. All of a sudden it doesn't seem like such a big gamble to see what the SS prop will do for me.

Nice touch, when you get it fitted let us know your findings