I live in Traverse city michigan and i recently bought a 1999 vyper with 500 efi's. It came with 30 pitch bravo 4 blades. I noticed that the props looked like they had been worked a little bit. The boat spins those props @ 5350 rpms ( too many rpm's i assume) and runs 73.4 mph. I expected the boat to run faster than that. I tried a buddy's 30 pitch 4 blade Bravos and the rpm's dropped to 5100, which is where i believe it is supposed to tach, and the boat only ran 70. I am confused. During takeoff, it feels like the props are spinning out. I believe my drive ratio is 1:5. Is 73.4 all i should expect out of this boat? I would appreciate any help .

I can't speak to the speed you should expect since I have only driven a vyper, which had 500s in it, once. That was in the fall of 1999. It ran about those same speeds in the test run at LOTO.

But as for the engines, I would prop them back where you had them. You should be OK running that RPM, I thought that was where the rev limiters were set.

the 38s run close to 80 with that power.......... I would think a 34 would be in the low 80's. Are you using a GPS or speedo?

Those speeds were GPS speeds. I was told to expect 77 mph at a bare minimum with that power.

Seems to be some variances in set ups. Rich runs 525sc motors in his 38 with stand off boxes and runs mid 70s. He gets his engines back this weekend with a top end rebuild that should put them around 575HP. It will be interesting to see what he runs with the rebuild.

One would think that a boat with that kind of power would be at least in the 75+ range. Sheesh my buddies 38 strait bottom avenger runs 70-71 gps with 500's. I would play with the props a little more. Maybe give Throttle-Up or BBlades a call. They seem to know their stuff. According to the prop slip calculator you are seeing 25% slip Good luck. BTW 73.4 isn't that bad

Where is HP500, he knows the history, but I believe PQ redesigned the hull of the 340 in 2000 to make it more efficient. I know newer 340's are capable of 80 with HO's, labbed props and light load. I no longer have the former and rarely have the later.

Regardless, that does not sound right with that power. Check for a hook in the hull.

I had a 99' vyper with 502 mags and the best the I ever got out of them was 74 at the LOTO in some rough water that gave me plenty of hull lift. I now have an 05' 38 and it runs 83 all day long with HP 525 EFI's on mild chop water. All these speeds are GPS.

I had pretty much the same boat new in 99 with a fairing and 500hps, mid 70's was pretty much it as far as speed went, and the props slipped alot so the boat planed like a pig,,putting the tabs all the way down helps alot with the planing issue but doesn't cure the problem, the boats strong point seemed to be in the mid-range cruising speed and the overall quality of the boat was great. P/Q did re-design/modify the hull in late 99/2000 and from what I've heard they worked alot better than the earlier 99's.

1998 and 99 hulls are a little slower then the 2000 and newer models, due to a redesign. Best I ever got was 78.8 GPS and run 75 all day. I should get 80 to 85 after rebuild, will see. I can tell you that if you are running it in mild chop that will slow you down these boats like big water and they handle it well. I also am running 30 pitch 4 blades so try props and water conditions. Good luck.


Rich.