Engine/tranny prop theory question

[85 Barefoot]

20 hours ago, The Hulk said:

agree with all above, my 555hp 2013 LSA 23lsv was a beast from basically idle speed, jumped like crazy and was only on a 1.25:1, with a 14.5x16 prop, and it could of probably handled 14.5x17+ easily. i ran 3000-3100rpms surfing slammed, 3200 if it was crazy day and wedge position but normally about 3050rpms was the norm. (never ran any bow weight) i felt no matter the bow rise the engine could overcome it, effectively pushing my boat straight up to the sky if i wanted.

2016 25lsv with 450(torque) and 1.76:1, i'm near 4200rpms with a 15x14.25, and it needs to be a 15x16 or 15x16.50 range to lower that. On another note i did put 800-900lbs in the bow and dropped all the way down to 3600-3700rpms (500rpm savings at a minimum for same settings)  while if i were to build from scratch i'd probably do the SC 572, but it just didnt happen too many other goodies on the one and the deal i got so i sacrificed from what i said i would never do but ONLY due to the newer 1.76:1 gear ratio. Yea i loose top end speed but its a surf boat after all, and i should have more torque at the prop than before or similar given how you calculate it. now with increasing pitch and some bow weight i should be able to get down in the 3200-3500rpm range and im pushing a lot more weight than my previous boat and got a better wave. I may not get quite as good as GPH with the smaller 450 vs 572 but its probably minimal difference over the 5yr warranty period i plan on owning it and being able to get 90/91 e-free on the lake (if i have to is huge) before i had no option needing prem gas (off the lake) - hassle 

there is NO substitute for the SC engines that generate such huge torque/hp at the lower rpm range and it is very noticeable, however as mentioned above is it worth the upgrade cost? kind of up to you depending on the options you want, personally i would go G4, stereo and other upgrades.

Now with steeper prop/shaft angle on the 2017 and a 2:1 im anxious to get those folks feedback on rpms, yea bigger prop and possibly higher pitch but do they come out the same? or do they actually need more bow weight to overcome the loss of shaft angle? im guessing its going to come out nearly the same, less slip, but more angular loss, i'm guessing it will be close but with the expense of at least "guessing" 4"+ more draft depth. and much more expensive props.

i'm plenty happy with the 450 for what i do, but i surely do miss the SC engines.. but shopping for a new boat it would be a harder sell than in previous years with the new gear ratios.

anyhow my .02

This isn't the first time you have referenced this.  Do you have evidence supporting that?  

[The Hulk]

@85 ..  No that's why I'm hopping some with 2017s can chime in.. it's just a guess based on what I've experienced in my 25 with either bow bag or people. 2ppl in boat and 800-900 up front lowered me 500-600 rpms for whatever that angle difference is .. I'll use a clinometer on phone to find out when I get back in the states. When I was loaded with people and when 2 -3 folks were in bow it was about 200-250rpms lower with them in bow compared to now bow weight.. so depending on how the weight is setup a little drop in bow makes a significant difference in rpms. The question though remains does that coincide with the shaft angle? And how much..... hopefully anybody out there with a 2017 25 lsv with a 450 can chime in with ballast/prop setup and rpms? Very interested.