Scarab 29 Top Speed
 

1997 Scarab 29, Twin 383 Mercuiser Mags (350HP each, stock), Bravo 1's with 23P Mirage props spinning out. I am only getting 65-66 mph @ 4,900 RPM's with drives out, tabs up. Shouldn't this boat be going faster? This model supposedly does 67-68 mph with stock 350 MPIs which I believe were rated at only 300HP vs the 350HP of my engines. Suggestions on getting more speed? Different props? I feel this set-up should be going 72-73 mph.

Bought the one out of NJ? Are the props Mirage, or Mirage Plus? Gear ratio in drives is 1.5? Yes, you should be able to run a bit above 70 with your power.

If you have 1.5 drives your slip is at 7.2%
Getting your rpms up to 5200 with same slip you would be hitting 70 mph
Reduce slip to 5% gets you to just under 72 mph

Are the motors tired, have a lot of hours?

make sure your trim tabs are going all the way up the 29 scarab i had had a spacer in the cylinder and would not let the tabs come all the way up put a straight edge on bottom of the boat to the tab and check that way and i can tell you a 2 or 3 inch shorty will really wake that boat up as far as ride and speed

Yes, I got the boat from NJ I was looking at. It's on Lake Norman now, in North Carolina, and will also be seeing time in Tampa, FL. I think the props are Mirage Plus but I'm not by the boat right now to 100% confirm. Drive gear ratio's I'm not sure. How do I check that?

The motors should be good. They are 2012's and have about 180 hours. All cylinders were strong when tested during the survey.

Rev limiter?

Mercury rates the 383 Mag at 4,800-5,200 RPMS. I think I'm turning about 4,900.

BTW are you reading the speed with a GPS?

Yes, the boat has a Raymarine system installed and it has GPS. I probably should double-check it with phone though too.