I test-drove this boat this past weekend. 1994 29' Wellcraft Scarab with the 502 Volvo DPX. I'm sure the speedo isn't quite accurate considering what I've read online, but the boat showed 50mph at about 4500 rpm. The owner had said it does about 60mph. We were in what I assume to be good water for speed. Not glass smooth, but not rough... just mild chop, if that's the accurate term.
I didn't work the trim tabs and the owner said he didn't mess with them much when he drove. They were all the way up when I drove it.
Is 50mph about what can be expected out of this boat? It shows 530 hours on the engines.
Thanks in advance. I'm new to shopping for a "big" boat and I appreciate the help. :)

I'm a fan of DPX drives, and have a pair in my Formula, with 600 hp each side. So far (7 years/280 hours), I've had one pinion gear go bad. Drive still worked, just burned the gear oil...
I would think that 60 mph would be a bit optimistic. If you saw 50 @ 4500, then 60 would be 5400, which is on the high side rpm-wise for a 502. Since it's a 1994 model, I assume that it's a carbureted engine? That would be 390 (prop) hp. The only way to really know top speed is to take a pocket GPS or radar gun with you.
The 1994 drives were known as DPX-S models, and are not quite as beefy as the DPX-R's introduced in 1998 and DPX-A's introduced in 2000. The good news is that the drive should be fine for any hop-up work that you have in mind up to 500 or 525.

Yep, it's carbureted, C_Spray. Good info to have. Thanks! I was hoping to pick something up that could do 60, but for a first boat, 50 with some decent wave-handling capabilities s/b fine. I don't know enough to know if trim tab adjustment would have gained another 1-2 mph or not.

I'm using a DPX-A in my 28 tunnel hull. Keep blowing out the bottom end. I was told by a volvo service dept. it may be prop wash, and to use an extension set between the upper and lower units. Any opinion from anyone? And also C_spray, got your e-mail about the E-3's. Have you checked to see if they are 3's or 4's?

The set I was thinking of are E4's. I have an extra E3 rear, however....

Lowering your drive may make sense if it's surfacing or close to it. The vibrations set up by the blades of each of the two props breaking/striking the surface of the water sets up some nasty harmonics and can wreak havoc with the pinion gear in the lower unit. (That issue isn't so bad in single-prop applications.)

Find one with twin sb's , I consider mine a bit slow @ 60 gps @ 45-4600 . 1994 merc 270 mags and alphas. Tabs , if bennetts are not very effective but do help when you want to stuff the bow. My bud has a 96 with mpi mags and bravos that runs high 60's. I had made the mistake of buying some gm crate motors and when I had them in her it only ran 53@ 4800 , had to drop 4" pitch in props te get them to turn up. I was not happy at all as stock the boat ran 60 from day 1. I wouldn't be happy @ 50 :(

Hey Guys, I have a 22' small power boat with a volvo dp drive. Bought it new in 1989. The only repair work on the drive in all that time is new universals. I am looking for something in the 27' to 30' range with a single or dula dpx. If anyone knows of something, Please let me know. Thanks in advance. Dave Hazen 319-931-3061 Iowa