Generally, what effect does a shortened barrel do on typical V-hull?

thx

Some single engine boats won’t plane with’m. Prop goes right into cavitation trying to plane. I , and another person, found seperately that if you block exhaust passage thru outdrive (you must have thru hull exhaust of course) then the prop won’t cavitate.

I have experience with a Bravo FS prop, which has a shortened barrel and almost no diffuser. I ran a standard 26P Bravo and a Bravo 24P FS on the same 2400 Checkmate / 300R combo ( amongst many other props). A 26p bravo with the diffuser and standard length barrel planed faster than the 24 FS. The stern lift was much stronger on the standard Bravo. It had less chine walking tendency but perhaps the 2 mph slower speed was partly responsible for that? The bow lift was much better on the Bravo FS with the shortened barrel and almost no diffuser. The rpm and top end were better on the Bravo 24 FS.

I'm running it(24p) on my Checkmate 270/496HO and couldn't remember if it helps bow or stern lift after BBlades lab? I don't notice much difference between closed and open exhaust getting on plane. So I guess it helps bow lift?? Also got about 100-150 rpm after lab.

thanks

Last night I shortened the barrel on a 24 Bravo. Will let you know the affects in a few days.

I did that to my twins end of last year but never got to test. So far my hull has reacted positively to every single thing I've done (trimmed strakes and went from spinning "in" to "out") to reduce stern lift and let the pad provide the lift instead. Not sure if I will get to test them this year either with $6 premium haha.

The shortened barrel works good on Nordic Heat. This 28' boat with a single engine is heavy in the nose (especially the open bow model) and has trouble carrying the nose at speed. It doesn't have a problem at all getting on plane and many of these boats don't even have tabs. So, in that example the shortened barrel works well. Hope that helps

On 26 Bravo's i cut off the diffusers. Have twin 502's on a 32ft Sutpen V-hull. Could not tell any difference in planning or top end. Surprising.

Another thought... will it require less "+" trim since prop now promotes bow lift?

I would guess that depends on the boat. If it lifts the bow more and frees it up to run faster, some hulls might be at the optimum or past and thus not require more trim but perhaps less trim. On other hulls that want more bow lift, you might still trim as far as before but the bow will be higher and you will still run faster. With the stock 26 Bravo with the diffuser, I trimmed my Checkmate to the stop limit. With the 24 Bravo FS it lifted more and I when I trimmed it to the stop limit, it did not slow down, but wanted to chine walk more. So I would run it at perhaps 2/3rds to 3/4 of full trim, which was still the same speed for my boat but handled better. Then with a 24 ProMax prop which has a straight barrel from the factory, more rake, more cup and 1/2" less diameter, that prop lifts both the bow and stern more. It allows me to run the hydraulic jack plate at least 3/4" higher, and that prop likes about the same trim angle as the Bravo FS (but the the bow and entire boat is higher), but handles totally different. At 30 mph I always have to run full negative trim and the bow is way up there almost ready to porpoise. Once you get over 45 mph it starts to push the bow down and you have to begin adding more trim with more speed. Almost no chine walk and very easy to control and at least 3 mph faster. (76 mph) However, if you fill the fuel tank and add a bit of weight the slippage increases with the ProMax prop and the speed falls off closer to the Bravo FS (but still a bit faster). That might be due to the smaller diameter.