Prop pitch on Formula 454 Magnum
 

Howdy folks... first post here. Hi!

So, I just bought a 1993 formula 252, it is a 25-26 foot boat, and weighs over 4K from what I understand. I has a magnum 454 engine, all stock (from what I've been told), 365HP. Bravo 1 outdrive.

The previous owner put a 4 blade prop on, with a larger pitch. He says he did it to "slow the engine down". Apparently he didn't like it revving as much on plane. The box it came in says it is a 21 pitch prop, and it is 4 blade.

This boat is a pig out of the hole though... with only 2 people it'll plane okay, but it takes a bit. With 5 people (most of them 100 lb teenagers) it would not plane at all unless a couple of them got up in the bow. I know it is a big boat, but I figured on better performance. On plane it peaks at 4K RPM, and won't go any higher.

He did give me another prop, that I assume is the stock one. It is a 3 blade, and it says "19P" on the side, I assume that is the pitch. Will swapping this other prop on get me better results?

I'm sure this is elementary to most, but this is the first boat I've owned myself.

Thanks,
Scott

What make or brand are the props. Also model and are they stainless. Are you trimming all the way down/in when taking off?

Hello Scott, The 19p prop should put you right where you need to be. This should really wake your boat up. Be safe and Good Luck!!!

Sorry I don't have the brand in front of me at the moment, but they are both stainless. I am trimming all the way down. This boat also has trim tabs... I haven't found much use for them yet, but I suppose they'll come in handy if I have an uneven boat load. I'm not sure if I'm a fan of them yet or not.

Thanks for the info, I'll get it swapped on and let you guys know how it goes. Hoping to get that done today or tomorrow and get it out tonight or tomorrow afternoon.

Putting the tabs all the way down will help you get on plane faster. Once on plane. bring them back up.

The 19P 3 blade is a "Mirage". Would this be the original that came with the boat?

that motor should rev to about 4,700-4,800 WOT. If staying with a 4 blade that would equate to roughly a 17P. A 3 blade 19P might be the right prop. It's one nut to change the prop. Swap them and go for a ride to see what it does. Hell, I've taken 4 sets of props out on the water and swapped them back-to-back-to-back standing in the shallows to test various props before.

Thanks for the help gents. I put on the 3 blade 19p (mercury mirage prop), and I got a way better holeshot. I would rev up near 3K when trying to get out of the hole (the 21p 4 blade was stopping it around 2200-2300 while trying to plane). It planes out much better. Now that I have learned out to use the trim tabs, that helps as well. I can also run it out now about 51-52 (GPS), WOT, and it peaks around 4800 RPM.

So, I ran it around like that all day feeling pretty happy with it and promptly ran it into a big boulder :picard1:. Rookie boat owner eh...

This lake has a lot of big rocks, and most all are marked with a big red buoy. Not this one. Fortunately, we were only idling, but a 50ton rock doesn't move much. it took about a half inch chip out of the skeg, and chewed up the edges of the prop a little, but it seems pretty minor all things considered. I'm more worrried about the outdrive. It actually just killed the engine. We putted around for quite awhile to make sure it was all working okay, then got it up on plane and everything seems to be running fine. I'll probably still take it in given the chance.

I may get another prop, and have this one cleaned up in the mean time and use it as a backup. I wouldn't mind even a better holeshot. I'm okay with losing a little top end... we would like to pull skiers, wakeboarders, etc... Would a 17P 4 blade work well? Any suggestions?

Another follow up on this. I got a 4 blade 17P turning point prop (14.5x17)... wow, did that change this boat. I'm pretty sure I'll pull up skiers on slalom no problem, with a few people in the boat. I mainly got the TP prop because it was cheap. I may upgrade to the rev 4 eventually. There is another prop called the "pleasure five" that I may try as well... it shows similar promise as the merc high five, but it is a larger diameter prop so it may be more suited for a larger boat.