Mjt 1969

I recently installed a 496 mag HO in my formula SR 271, I've been playing around with props and trying to find The right one for general all-around purposes. Does anybody on here have the same set up, or any suggestions as to what prop I should run. I currently have a Mirage plus 23 on it and that prop is spinning up to about 4900 rpm's, but it feels like the boat needs, or wants more push.Any recommendations would be greatly appreciated

Griff

Your WOT rpm is near perfect. What GPS speed???
A 22 Bravo 1 might give better cruise speed but would probably lose aaa mph of top end. Maybe try a REV4 also.

Mjt 1969

A rev 4 24p or a 22p?

Mjt 1969

My wot with the 23 is about 58-69 It feels like the boat wants to go faster, my mid range is around 50 at 3800 or 3900 RPM's. I borrowed a Michigan stainless steel prop Michigan supposedly copied a mirage 23 and the Michigan 23 put me at 50 miles an hour at 3800 RPMs and 60 mph wot but that prop would only spin up to 4600 rpm's, it's unbelievable how much of a difference there is in props of the same size but different manufacturers. i've been told by a few people to try to bravo 1 24p for best all-around performance

class6

Rev4's are odd #. A 23 is bigger pitch than a 24 B1. A 496 propped right should touch the rev limiter in perfect conditions. I think the stock limiter is set at 5150.

goran271

Hello to all from Croatia (didn't find new member section, so maybe I'm little parachuting into thread )

Also similar question as fellow member above. Recently I purchased my first ever boat (1993 271 with 496 Base), after lot's of reading and "learning", and of course with boat I've got my first problems free of charge .

I'm running Bravo 1, Mirage 23P, on my 496 Base WOT rpm is 4800 I think, but I only got it to 4650.. On 4650 I'm having only 49-50 MPH GPS. I think this is bad.
Sadly I don't know my Bravo 1 gear ratio. All labels are unreadable. Do I need a bigger prop? (Besides of raylar kit :P)

Am I wrong assuming that this boat with 375hp, perfectly clean hull, runing in salt water @ sea level, on a cool day with no wind should to something close to 60 GPS ?

Griff

Your WOT range for a 496--375 hp is 4400-4800 rpms, so you are in the correct rpm range. Its a heavy boat for that amount of power, so the low 50's mph range is what I'd expect it to be.
Are you sure you have the drive trimmed out for max speed??? Tabs all the way up???

goran271

Yep

tabs all the way up.

when trim is at lowest position i can make 4400 rpm, then I trim it to 4600+ and gain a little speed.

do you think it would be able to plane and wot with let's say mirage 25P?

Mjt 1969

The WOT rpm range for a non HO 496 375hp motor is 4200-4600 the HO model is 4800 wot,there is a rev limiter set at 5150rpms but I don't think I'd want to push the motor that much, I prefer to stay within the manufactures specs, I have the same boat with the 496ho in it with a 23mirage on it I'm right at 60mph wot, it feels like it wants to go a little faster at wot because I'm spinning 4800 with very little trim and when I give it more trim my rpm's climb but I'm not going any faster, I have a bravo 1-24p coming from bblades to test. I don't run wot very often so my goal is to have good mid range but when I run wot I want that push the 23 doesn't seem to be giving me. At the beginning of the season I borrowed a Michigan Ss prop which isn't a real performance prop and I got real good mid range with that prop at 3800 or so I was right at 50mph but when I went wot that prop would only spin up to 4600@60 mph, same pitch as the mirage but totally different performance that's why I'm trying the 24-4 blade as was recommended just to see how that does, once I get it I will post results, but you're prob at your max with the non ho 496 at 50-55 wot, as stated they are heavy boats 5250 lbs is what my owners manual states

goran271

I think I'm going to try 19P to see where the rpm limit is, to see how is rhe engine reving, and than I could try with 25P mirage to maybe reach 55 for this season.

For next season I have 3 options:

tune my 496 with raylar stroker kit, heads, intake (hope to see around 600hp)

buy this month one used 600 sci (60 hours)

third option is to buy from Marine Power LSA small block with 550hp

if I go with first option, I would like to buy one used/damaged engine block from 496 to bore it, install new heads,cams, pistons and so..

then my stock 496 is free to sell to somebody..