Re: Educate me again on prop efficiency
Thanks Chris...they are Solas Amita's...2 questions...if I find a 3 blade Laser II..pitch would be?...and will a Yamaha/Evinrude prop fit my Alpha 1?...all I have close to me is a Yamaha/Evinrude dealer...Thanks again...Bill
Edit..the Alpha 4 aluminum is not available in 19 according to my findings...will 20 pitch be too much...or go to 18...
Quite right, the Alpha 4 is only in even numbered pitch...I would try the 20". As for the difference in 3 and 4. I also agree that the 4 blade is so much a nicer/smoother propeller. BUT.... it is LESS efficient. As for the difference between Solas and Merc props, I'll deal with that in my answer to jestor. (You'll find it interesting)... Oh, and you can't use a Yammy or 'rude prop on a Merc, splines are different... (They are also not as good a props... IMHO)....
Not sure if I'm hijacking this thread...
But I'm actually not certain what the pitch was on my 1.84--might have been 19". Either way, the way I'm propped now with a 1.98 gives me similar top speed and WOT RPMs as the prior setup. My question was more hypothetical. That is, at a given engine rpm, is there a difference in performance between using a higher ratio/bigger prop v. a lower ratio/lower prop? The bigger prop is spinning faster, so maybe more inefficient if the slip stays the same--but IDK if that's true or not. Or put another way, is there any disadvantage to using a different drive ratio if you're able to size the prop such that you get recommended WOT rpms (and therefore the same engine load)?
For the same engine revs, the higher reduction ratio/higher pitch prop will be spinning slower, not faster. That will make it more efficient. As for using different ratios and different props that keep the revs in the recommended range. It's personal... But I can say the following...
My previous engine was a 1994, 4.3LX with a 1.84:1 drive ratio. With a 21" prop that boat was fantastic. Handled well, accelerated brilliantly and topped out at 40 knots... Loved that drive/prop set up.... Fast forward to 2006. Sold the LX and dropped an MPI in. It came with a 1.62:1 drive... Sold all my 3 and 4 blade SS props from the 1.84 and bought a bunch of SS and ali props for the 1.65. Now needs a 17", and I can feel the difference and I really want my high pitch props back!!!
I think that if you talk to the engineers at Honda, Yamaha, and some other OEM manufacturers (who trust Solas to make their props), you will hear different opinions concerning the design, quality, and efficiency of Solas props.
2 reasons... It's about the money and not giving Merc the satisfaction of acknowledging the superiority of their props. Solas props do have a higher level of polish on them, so they LOOK higher quality... Example. Have a friend who bought a new boat. Had a V8 in it and he was running a 17" 3 blade ali Merc prop. He wanted a SS, and being a cheap bastard, bought the Solas, as it was half the price... But he needed a 23" to keep the revs down to what the 17" Merc prop had them at. I loaned him one of my 4 blade SS props, a 17" 'Offshore' (Merc prop now replaced by the 'Vensura' series) and the revs were exactly the same as the 23" Solas.... Now, you tell me which one is not efficient....
No hi-jack nola...but yea,great question...my thoughts exactly...I was thinking that maybe you can put the v-6 unit behind a v-8,but you may have trouble going the other way...v-8 unit behind a v-6...IDK...lol....but I'm learning lots here and feel I'm getting the right info ...kinda...sorta..and that doubt being directed at what jestor68 stated....Solas seems to be in a lot of places and you do get lots of review info if you search...I'd say my findings have been neutral...which leads me to ask the same type question as jester...how?...they are sold here and I own 2 of um...the quality looks great but my knowledge on performance of anything sterndrive is minimal at best...but Chris is dead on with my scenario...and he's never been on my boat...so I respect his knowledge and info given...that's exactly what it seems like...more slip than bite..especially when planing....if I ease the throttle up... it planes much better over the other set-up...effortless almost ...smooth....no vibration...compared to the 3 blade set-up...but until it lays flat the slip seems to be a bit high....much like cavitation would be if you trim to high...although it's tucked all the way under and is not venting...the results were the same if you left the trim neutral to the boat bottom...no negative tuck...all I seen different planing at this setting was higher bow lift...but the "slip" seemed the same...I was gonna order the 23 pitch to get the wot down hopefully... but that is on hold till I get a little more education on the matter...I would prefer aluminum over ss due to strikes in our area...but 23 seems to be tops in alum Solas 4 blades...I also feel 23 would get my wot r's in range.. given a 400 rpm drop happening by going from 21 to 23 pitch..."chime in...anyone?...the engine seems to be happy and under no load at all with this set-up...almost like you 're overpowering the prop maybe...I'm green on sterndrive...but damn I like this boat...even propped wrong....or right...idk...there's some smart peeps here...we'll get it....I'm confident....Bill
Hey Bill... I guess you've read my replies above and that pretty much covers your questions... I hope...
If you want a 4 blade ali, try the Alpha 4 in either 18" (better hole-shot, but could take you a bit over the top on revs) or the 20" (may leave you a bit shy on top revs, and will feel a bit 'doggish' after the lively feel of the shorter props).
As for putting a V8 drive behind a V6 engine.... In a very small light boat you would do that to use a shorter prop if the prop on the 'standard' ratio drive was too tall to find in the normal sort of propellers available.
Chris........
