Lab finish or leave as is
 

My Fountain 38 Sport Cruiser [loaded down with generator,AC fuel and etc] turns 23 Hydro Quad 4s 4950-5000 RPMs and 64-65 on GPS. Would lab finishing be worthwhile in this speed range? What would you expect for an SC?

My boat responds well to stock merc props. I've tried labbed props with little to no speed increase although my rpm has increased (higher slip #). I would try some 24 bravo1's before labbing your hydro's.

Bob

I just bought these Hydro props to provide more sternlift as needed for twin step hull design I believe these are the right props based on Fountain info and personal research and Merc props would also work. Really, I don't want to switch props again. Also 23 Hydros are equivalent in pitch to 24s in Bravo specs and rpms are where they should be. I picked up 3mph already and am very pleased with Hydromotive but just wondered if others had seen increases with similiar boats and similiar speeds -mid 60s when lab finishing. Its not worth it to me to get half a mph but 2 would be good enough .

What engines???? Do you want more rpms????

I'm running 502 MPIs @4950-5000. I could pick up a little rpm maybe up to 5100? but already am near the top of recommended rpm band. If lab finishing would get me 100-150 rpms that would probably be ok and under the rev limiter.I wonder if it would?

You could have them labbed with added cup and increased pitch to keep the rpms about the same, and you would still pick a few mph.

You can Lab the propellers and gain some top rpm and top speed (.5-2 mph, smoothness and throttle response). It is a balancing act with those props as far as losing mid range also. Make sure the it is done correctly.

You picked up 3 mph already from what propellers before?

Hydros can give better top speeds on Fountains out of the box only, compared to B1's, but rarely improve and often decrease midrange speeds. Especially on SC editions.

The props on the boat were 23 Mirage plus put on by the prev. owner for no good reason I can come up with. They slipped lacked top end and felt very unresponsive in acceleration. With the 23 Hydro Quad 4s much better all around.The difference made me think that props must be about the best way to increase in efficiency. It sounds like you prefer the Bravo 1s if I lab them on this twin step 38 SC.

I do like the B1's better especially on the SC's. It's not that the Hydros aren't good, they are. It's just that the B1's have better mid range where you spend most time running.

It's no doubt you picked up performance over the Mirage + props on that boat. What you really did was harness the slip issue.

You already own the Q4 props and they are running in the 10.71% slip range. Having them Labbed to gain 100+ rpm is a fine idea. You will see some acceleration and smoothness gains.

B

Thanks Brett for your input. Sounds like a winter job when the boat is put away this fall. Would the reliability of the props be a concern with this work? Also if you don't mind, what would be fees are we talking here to do the job right?

How about buying a set of props that are 1-2" pitch larger than what you run normally, then have the bigger props labbed?

Can that be the best of both worlds (Cruise/Top End)????

I've heard of some labbed props loosing shape over time and blades breaking from being thinned. Any issue with that??

Going up 2 inches of pitch and Labbing to get the R's back is always the best move. Or if you are 200-400 from your top desired rpm. Going up in the pitch does reap the better of both worlds. The down side is only that a small amount of acceleration can be lost going to the higher pitch. However the Labbing does bring most of it back.

Pat,
What HP are the 502MPI's? Just wondering, I am rebuilding to around 425HP this fall, I'd be satisfied to see 60 even (knowing that I am 2-4 mph down for the classic hull).

My engines are 415 HP @ the prop. 500 hours on them.You should be over 60MPH with that power.I'm not sure what props would be best for the traditional hull but I'm sure Brett wil know.

Thanks for the info Pat. I'm running 21's now (embarrassing as it may be).

Can't wait to get these motors out......about 60 days to go!

PJ. What speeds do you top out at and what power do you have currently? It will be interesting to see your gains. One guy I spoke with had 390 prop hp/502s, traditional SC hull & ran 24 Hydro quad 4s.He turned 4500rpms. Sounded a little low to me. I was shooting for 4900.

Well, I'm too messed up this summer to even really give good numbers.

In flat water, no wind, I can get 48 out of it. Blew one motor end of June, replaced that one with a mag, that side blows out badly after about 4500 rpms (spinning 21's)

I have 2 GEN IV 7.4 MAGS that will be built a little beyond the old merc 420HP specs (making them full rollers), hoping to see around 450-460 HP per.

I will have to play around with props quite a bit I imagine, I was thinking I'd be into a 25P, not sure what that equates into a 4 blade.

I have a buddy who runs a stepped hull, he has cleavers, a lot of other heavy boats I have seen lately have 4 blade, is there a reason for that?

I'm honestly more interested in cruising speeds, I would be happy to see anything over 40 mph at 3400.

The OEM valve covers on the motors going in this fall are telling me the max operating is 5000.

4800 to 4900 would make sense to me topping out.

http://www.offshoreonlyclassifieds.c...o20110-en.html

1 down or 2 when you add a blade?

Pat, you ever had to replace your drive/tab indicator cables?

That's another thing on the winter list.

I think 25 pitch may be a little much if you are trying for 4900 rpms unless you expect to be up close to 70 mph. The 23s get up to 65 mph, 24s maybe 68mph.For me the 4 blades raised the cruise speeds significantly. I would definitely recommend 4 blades to lower the slip %. 3 blades didn't bite at all. My cruise @3300 rpm speed is aprox 42-3 mph. No,haven't ever changed the drive trim indicators. I have to rely on my mechanic for any work of that sort. Those Hydro 24s look pretty good and fair price but I'm cautious to buy online unless on e bay since I was sold wrong pitch props last year on some online site with no exchange. Your boat sets in the water higher in the stern and lower bow due to the hull design. I occaisonally tie to a nonstepped 38SC at Jellyfish Joel's @ Fairlee Creek. You may want to start a thread to see what other SC owners run on traditional nonstep hulls.

Thanks again Pat. It will be a trail and error session next spring I suppose.

You ever make it up North towards the Sassafras or North East River?

Phil

The Sassafras is great. We usually get up that way a couple times a year but haven't recently. Mostly running to Fairlee Creek and Rock Hall this year. If we get up that way I 'll look for you. My boat is dark Hunter Green and Gold striping named Fountain of Youth.What are your boat colors ?Do you get down the bay?

I'm black with some blue/yellow striping (dated scheme). No name as of yet.

We do not get down that way, partly because of fuel, party because I've never been that way on my own (scared).

I'll keep an eye out for next year.

I'll keep an eye out also.Gas prices are an issue for us also. We do more shorter runs now.You may want to consider a gps and the chesapeake bay chip to show markers and depth, tides etc.if you dony have one. Prices are good online if you look around. It really makes exploring easier and less worry about those props. Sounds like you have enough on your plate this year.

I have the gpsmap476, pretty nice unit with really nice detail.

We dump in at the back of the North East River, usually go out to the flats, maybe over to the Sassafras or up to the Chesapeake Inn for dinner/drinks. (25 mi. round trip).

Hopefully next year will be nicer on the wallet, hoping gas prices straighten out. Hoping also that next year I won't be dumping ~$10k into the boat............:(