2012 Yahama 115HP 4 Stroke Prop Size

[Tinshack]

Hi All, finally after many years of debating, I have upgraded from the trusted 1994 model V4 2 banger to a brand new 2012 model 4 stroke 115HP yammy;D.
I current have a stainless steel 13 1/2" x 15" pitch 3 Blade Solas New Saturn prop on the 2 stroke & can obtain 5900rpm WOT with 200L on board but no fishing gear. Boat is 5.5m Southwind Cuddy Cab & 1300kg loaded with 20 Deg deadrise. I see the new 4 stroke has a gear ratio of 2.15:1 & the old 2 stroke had 2:1 ratio. Also the dealer has said the 4 stroke WOT should be 6000-6100rpm.

What has been the experiences from those who have upgraded from 2 to 4 stroke with gear ratio changes & prop sizes.

Get boat back on Friday & will test run with same prop & see if I can get 6100rpm WOT with same load or may over rev?

Appreciate any advise,
Cheers,
Dave.

[gofishin]

Hi Dave,

That change in gear ratio is quite small, however at least it is changing in the right direction to get a couple of extra revs from the new ratio. Whether the 4/ will spin it as high depends on the torque (hence power) developed at WOT. You could have a browse through the US EPA site and compare actual HP for the two, though it might be a bit hard to get data for the old donk. As a matter of interest 5900 is pretty high for a 2/ !

Haven’t done any prop testing with V4’s but I can say that even with more torque from the new big block yammy V6’s (and they have 'oodles'), the new ratio of 1.75:1 (compared to 2.0:1) means that a drop of 2 to 3” is required in pitch - for the same boat & HP.
Cheers
Brendon

[Swanie1975]

hi dave not a yami i know but i recently repowered froma suzi 2 stroke to a suzi 4 stroke. both were 140hp on a signature 550br. what hp was the 2 stroke?

i had loads of fun (not:() getting the propping just right how i wanted it so the new motor would give me holeshot as good as the old 2 stroke did. after trying 2 suzi factory 3 blade props (19 and 21p)which i could over-rev, i tried a 4 blade solas prop that was recommended by solas and while it put me spot on at the top of the rev range the holeshot was woeful and the fuel usage was up on the 3 bladers. speeds approx the same thru-out the rev ranges.

i ended up ditching both suzi and solas and tired a mercury trophy plus(4 blade stainless) in a 20p and am stoked with the result, great holeshot better at lower revs and mid-range with a 2 kmh reduction in top speed over the 3 bladers (still 71km WOT);D
the fuel usage is about 2-3 litres less per hour with this prop over all the others so finally im happy with the performance of the four stroke over the two.

good luck with the set-up and once you nail it you will love the huge difference in noise, fuel use and smells over the old motor!

cheers ryan:)

[rocklobster]

The new saturn is more of an all round prop and designed for "work boats" if it came from solas here they will exchange it for a fee and try some thing else like a HR titan in either a 3 or 4 blade . The Merc props also seem to be of high quality and from what i read the revs 4 has good reviews .

[Tinshack]

Hi Ryan,
2 stroke is same, 115hp. I have done extensive trials on the 2 stroke, 17" pitch, 4 blade 15" pitch, raising the motor one hole & eventually settling on solas 3 blade 15" pitch as it gave me best ecconomy/performance is swell offshore. Attached is the fuel flow readings I got with the 2 stroke. I am assuming the 2 stroke prop rpm is 5800/gearbox ratio 2:1 = 2900 prop rpm. The dealer is saying the 4 stroke WOT target is 6100rpm fully loaded, so 6100 / gearbox ratio 2.15:1 = 2837 prop rpm. The rpm difference is peanuts, I just do not know what the torque difference will be at WOT, will be best to do trial with existing solas 15" pitch prop & see if WOT 6100 rpm is exceeded.

The holeshot performance will be interesting as they have gone to a longer single throat intake on the Yamaha for the 2012 models to better perform closer to 2 stroke performance. Looking forward to checking the differences.

Yes the dreaded fuel bill & range was the final factor to do the change. I loved my 2 stroke but I think I will love the 4 stroke more every time I fill up.
73973
Cheers,
Dave.




hi dave not a yami i know but i recently repowered froma suzi 2 stroke to a suzi 4 stroke. both were 140hp on a signature 550br. what hp was the 2 stroke?

i had loads of fun (not:() getting the propping just right how i wanted it so the new motor would give me holeshot as good as the old 2 stroke did. after trying 2 suzi factory 3 blade props (19 and 21p)which i could over-rev, i tried a 4 blade solas prop that was recommended by solas and while it put me spot on at the top of the rev range the holeshot was woeful and the fuel usage was up on the 3 bladers. speeds approx the same thru-out the rev ranges.

i ended up ditching both suzi and solas and tired a mercury trophy plus(4 blade stainless) in a 20p and am stoked with the result, great holeshot better at lower revs and mid-range with a 2 kmh reduction in top speed over the 3 bladers (still 71km WOT);D
the fuel usage is about 2-3 litres less per hour with this prop over all the others so finally im happy with the performance of the four stroke over the two.

good luck with the set-up and once you nail it you will love the huge difference in noise, fuel use and smells over the old motor!

cheers ryan:)