We had a beautiful day up here in Northern Michigan so we spent it on the boat. On the ride back the lake was like glass, doesn't happen often in lake Michigan. The boat is one of only a handful of diesel powered boats the Hustler built. Cruising back and playing with trims and throttle positions taking advantage of the glass and I learned a few things. I set it at WOT and watched the fuel burn rate and the load percentage and slowly backed off until they started to move. Around 3/4 throttle the numbers started to move. So basically 3/4 to WOT does nothing. I started playing with the drives and noticed something interesting. Trim numbers are -4 through +4. I zeroed in on -2, thats where I get the biggest rooster tails. When I adjusted the trim ever so slightly I would lose MPH. I mean negative 1.75 or positive 2.25 it would scrub off a couple MPH and the RPM stayed steady. Now, if I trimmed up and gave it more throttle RPMs would go up and so did the MPH. Anything after -1 it will start porpusing by hitting the slightest boat wake or wave. About positive 1, it starts porpusing no matter the water conditions. I can squeeze 10 MPH out of it letting it porpuse a little. We're building new higher RPM and higher HP Cummins, hopefully this winter. My question is, if the new motors can spin the same RPMs I get when I allow it to porpuse down at the negative 2 trim, would I see more than the extra 10 mph since it seems the negative 2 trim is what the boat wants? Or would it just be the 10 MPH gain but at a better, flatter, stable ride? 480 HP Yanmars, #8 Arnesons, with 18" x 32P x 18r props, and 1.10:1 transmission ratio.

The boat you now own originally belonged to a neighbor of mine out here in California. I'm not certain I can help you out with your v-bottom, but I can tell you of my experience from having owned an ASD 7 Skater for over a decade, as well as having known Howard Arneson very well for over 3 decades until his passing (RIP). With a shaft drive setup that you have, the propshaft centerlines are much higher than those of a standard vertical shaft style surface drive such as a Mercury #6 or #8 drive. The mechanical differences in how they trim up and down are also very different, which causes the boat to react very differently to trim. With a shaft drive boat such as yours, trimming up typically isn't going to help carry the boat such as a Merc drive would, it's only going to start raising the props out of the water. I think the problem you're having is that the boat will go faster as you start bringing the drives up from a highly negative trim setting until the props start becoming so high out of the water that they no longer have enough bite to carry the boat, at which point it drops the bow and then sets the boat into a porpoise as the props gain traction/lose traction as the boat porpoises. My Skater 30/ASD 7 boat was very rake critical on props, it would porpoise really bad with higher rake props. With 14-degree rake props it's porpoise range was 60-90 and with 18-degree rake props it would porpoise from 60-140. I'm not telling you what rake props your boat is going to like, as it's a v-bottom and not a cat, but I'm positive that the answer to your porpoise and speed problem is in props. You need to test, test, test all the different sets of props you can get your hands on. I would first try low rake props - 14 or 12 if you can find some - and if those don't work for you, go the other direction - 22- or 24-degree rake. Because of the mechanical limitations of a shaft drive setup not being able to actually take advantage of positive trim to help carry the bow, you're relying on the rake, diameter and number of blades/prop design to do all the work. I would also try some round-ear cleavers to see how that work, as they will provide more bow lift than a standard type pointy-eared cleaver. You've got a really cool, unique rig and it's just a matter of testing, testing, testing props until you find what gives you the best results. Swapping rotation will also have a big effect on how the boat carries - which with those ASDs means swapping the drives from one side to another (a lot of work unbolting them from the transom, I know). Anyway, good luck with your quest to dial your boat in, I know you'll be happy once it's done!

Round ears, lots of blades, lots of blade area and high rake are the tickets to bow lift.

Skater30, thanks for the reply. I picked up the boat winter of 18/19 and from California. So Im onlybthe second owner which is rare for a almost 20 year old boat. I intend to keep her forever. I tried a pair of 17.5" x 34p but couldn't get on plane with them. That small difference between 18 and 17.5 was too much. I picked up a set of 18 x 32p 4 blades off ebay for 800 bucks! They are labbed Herrings, for 800 I could not pass them up. I put them on only long enough to see if they would make a good set of spares. They got on plane and I run it up to about 70 then pulled them back off and put on the shelf as spares. Unfortunately there are not many 18" props laying around. With the new power Im thinking a 36p 6 blades. I noticed a lot of guys running surface drives are running the 6 blades. A buddy just switched from 5 to 6 and said he lost a couple MPH up top but gained everywhere else and the boat just rides better. I just thought it was very interesting that the boat wanted the trim exactly at -2 and anything above or below that scrubbed off speed at the same RPM. In my head that tells me that is the most efficient setting for my current set up. I'll keep searching the internet for any 18" blades. Also, after the repower, I'll be starting over. My plan is to run the current blades with new power, take a ton of notes then call Herring or B Blades.

Different animal but I have a 38 top gun and have to run 18 inch also. With 525's and bravo's my top was 86. After the Arneson's were put on I was at 95-96 mph on 5 blade 18x30x18. I put 850's in and run 18x35x18 hitting 108 not with correct props. I ran a set of 18x37x18 and saw 110 hitting the rev limiters. My boat likes a foot of chop to really perform. I could probably gain a few more mph with different props but I have learned that someone is always faster and really don't go past 60 mph. Post some pictures of your Hustler, very cool boats.

You went from 86 to 96 with the same motors? Wow. Step TG I assume?

There is some good information in the posts above, what I have found with my Arneson stuff is prop testing is key because what prop might work in one boat might not work well in others .With the trim settings I measured the thrust tubes to find where neutral sitting was and I would never go above that because all it was doing is lifting the props more than half out of the water and was not gaining speed.

What hp are the new Cummins going to be? is that a 32' or 38'?

Its a 40. We're shooting for 800hp at 3600 to 3800 RPMS