42 fountain prop help
 

Boat runs great with 32 pitch 4 blades. Tough to get on plane, but decent overall. Tried a stock set of maximus 30 pitch, hoping to get on plane better, and have better midrange. Results are not what I expected. Almost impossible to get on plane. The boat keeps blowing out anywhere over 3000 rpm. Under 3000 rpm it does not want to pick up speed to plane off. Have tried tabs in all positions, drives are tucked. Usually 4 people, and 100 of fuel on board. 2004, 525 boat.

Strange. Do you have any history on the props?
Have they been repaired or worked?

Brtt

Thanks for chiming in Brett. Stock maximus 5 blade 30's. full diameter. No repairs or work I'm aware of. I switched back to 4 blades just to make sure I didn't have other issues. They were fine. It was a 1/2 mile balancing act to get the boat on plane with the maximus props. Could my drive showers be to close causing cavitation or something? Just thinking out loud.

Getting more blowout from the maximus props over the bravo 1's seems strange for sure. It would almost seem like you need higher pitch but it totally makes sense to go from 32 Bravo's to 30 Maximus..

What drives / lowers are on your 525's? Is it a full stagger? If they are short sportmasters, you might have to remove the splash plates using full diameter maximus props. I've had good results with the max's. Went from 6-blade Herings to max's and got less blowout.

Standard drives. I would guess my drives are a touch deeper than most 04-05's. boat is a full stagger.

That is very strange. Are you 100% certain that the max props you have are box stock? I recently bought two maximus props from someone who told me the "only" thing they did was take them down to 15 1/2 diameter. I ran those props and got terrible results. I then ran the out-of-the-box stock maximus props there was a 10 mph difference and planing and handling was totally different and I thought the "only" difference was 1/8" diameter. No complaint about the seller I bought the props from because they disclosed that previously, but I couldn't believe there would be such a difference and there was. If you're certain they are stock, then I'm stumped. You might try removing the water pickup from the drive shower to see if that makes a difference but put a cap bolt in there with a nut on top of the cavitation plate so you don't leave a hole in the plate.

I agree with HyFive that it seems there might be some "repair work done to the Max props.

Also, I don't like to install drive shower pick ups more than 1/2" below the cav plates. I'll go shorter if possible. They can cause a cavitation bubble that can disrupt the high pressure on the face of a propeller blade upon planning or once under way.

Brett

Did you ever try new stock 30 maximus props and get results? Thinking about the same thing.

Any updates?

I'm running 30 maxs on my 04 with 525. Drives are sport master shorties with 1 inch spacers. Had to put them in because stock maxs would hit cavitation plate. Had BBlades cut and rework them to work without spacers. Boat runs stronger and has more mid range acceleration than before.
Next is to take spacers off and try that. Planes great with the 30s, much better than the bravo 32s.

Thanks 388.

Hear you on this one, My boat runs well on stock, not been F'd with, 32 Bravos, 91-92 all summer in the heat with peeps and fuel. Few years back during one of my many test some wheels sessions I ran a set of rented and stock, so claimed, Merc Maximus 30's, along with many other sets the same day, and opposite of what was to happen did happen. The stock Maxes were dog chit, hard to plane, mid range was fair, but not outstanding, top end performance and handling was a major chit dump.

We can fix that!

Will you guarantee that ?

Well you know all things propeller are a mystery, send much money and hope for something less than you hope for.

Kinda works like that!

Occasionally the Maximus props won't improve planning and mid range efficiency over the Bravo 1 props. However, this is extremely rare.
It isn't rare that the Bravo 1 props will have the better top end speed but if the slip was high with the Bravo 1 props the Maximus props may still have the better top speed.
We have done more Fountain Bravo 1 to Maximus upgrades than one might realize with extremely good results.
When we do this we Lab the propellers 90 + percent of the time to get the best numbers. We change the Maximus recipe to fit the owners desires per the performance numbers from all previous sets of props as well as boat attitude. Usually something unseen prevents the Maximus props from doing what they are supposed to do.
But, agreed, after a lifetime of boating and 25 years of being in the profession, I still see things that don't make sense and just can't happen. Hopefully we all keep learning and growing and testing.

Test, test, test.

Brett