PROPer PROP for PQ 280 silencer
 

Whats the recomended prop for my Power Quest 280 silencer? It is basicly stock with CMI headers and K@N filter system. It has a Performance Bravo one 1.5. Low water pick up with the aluminum spacer "because the step hull i assume?" It curently has a 15"d 26P Bravo one 4 blade. It plains out very fast and runs mid 60s "65" on GPS with half tank "50gal" , 4 people and a cooler full of beer. Ive heard that you get more speed from a 3 blade and ive heard alot of good about labbed props. My prop isnt even polished, Its just machined. Useful input would be nice.

Thanks.

The Engine is a 502 mag MPI also.

What RPM are you at WOT? You should prop that motor for 5K RPMs.

What RPM are you turning right now? Whats your engine rated at for max rev?

Sorry just seen your post... Yeah, this info is a big variable left out

it says 4600 to 5000 on the valve cover. It turns 4900 at top speed.

I guess its about right then huh?

You are getting 16-18% slip currently. All things considered not so bad of a current prop if thats your typical load. With some labbing you may be able to pick up 1-2 maybe 3 mph if they can get your slip down to 12% or so depending on bow lift ect. Contact Brett@BBlades or Greg@Cutting Edge. Maybe they'll have some insight for you on the specifics of your hull ect...

Slip meaning lack of bite the prop is getting on the water???? Is the higher % of slip meaning its closer to blowing out?

First thing's first. It does not sound bad. Maybe a little cupping and less pitch is all you need.

The answer to this question is not a straight forward one. Slip is not a bad thing, but there is an optimum amount for a particular hull and setup. I've got few a question. You say that your prop is 15" in dia. and has a satin finish. That means someone has worked it at some point. The stock B1 prop is 15.25" in dia. and has a gloss finish. When you say that there is a spacer in your drive, and you have a performance lower. Do you mean an XR sportmaster shortie? How deep is your propshaft centerline relative to the keel? It sounds like you're running good. If your prop sits high, and you run a slip of 16-18% with a 4 blade 15" dia. prop, you won't gain much from a 3 blade. You might not even be able to get on plane. If your current prop is indeed labbed to 26" p and 15" dia, and I suspect it is, try a stock 26" B1. It is actually much more like a 25" pitch, and have the bigger dia. This should bring your slip down and give you some rpm's on top. If you go on plane fast, i'd suggest you also try and remove the spaver and see what happens. The increased dia. should enable you to run the propshaft centerline closer to the bottom. Oh, and the spacer has nothing direct to do with your hull being stepped.
To sum up, this is what I would do, becarse I think dialing in is fun:D Contact a prop shop with test props and get a 26" and 24" B1. Also get a Maximus in 24" and 25" both in 15,25" and 15,625" dia. Then try everything with and without spacer. Dialing in is a process and you'll need test props and patience to do it. A place to start for test props if the local prop pusher can't help, is Bblades, and of course the guys you boat with. Bblades, DAH propellers ect. are also good places to get what you have now worked.

Good luck with it.

I just measured it again and it is definatly 15" on the money. and it has no shine to it. so it prob has been messed with. It isnt an XR. It just looks different than all my buddys Bravos. And it says Performance Bravo One on it instead of just bravo one. And it has a low water pick up so you cant hook it up to the muffs you have to use a boot. I was tild by a old PQ dealer that the spacer is to help reduce the chine walking that the 280 silencers are bad for. But i am all about dialing it in to get the most out of it. I had my old 20" open bow running 73 with a mild built small block and it took a few years to dial it in but thats about all it had. LOL. I realised that the big block boats are a whole new league and im really liking it!!!!

Pics of the Bravo.

Is there any difference in this bravo or is it just a different mercruiser decal?

I just did some research. There is a difference. Its like an X drive. A step under a XR. It is $1000 more than a standard Bravo one.

I calculate your slip at about 17%. This is a touch high but not ridiculous.

Bravo 1 props are approx. 1 inch low in pitch plus the cup height causes me to use 15.3 in my calculations. The props are actually 15" diameter not 15.25" as they are stamped. The 34 and 36 are 15.25" diameter.

The prop is most likely worked if it has a brushed/satin finish. Look in the inner hub area for any stampings or markings. There may be something we can do to the existing propeller to improve performance. I don't feel your performance numbers are too far off considering the HP/hull set up. Most likely we can improve the performance using your existing prop.

I would also be interested as to the depth of the prop shaft centerline below the bottom of the boat directly in front of it.

Brett