speed ?

[Travis Petersen]

i have a 78 mako 21 footer with a
700 horse 468 roller moter, a berkley jet drive, top loader, place diverter, no hook
it planes out with only about 3 1/2 feet of boat riding on plane im wondering if any one has any suggestions on how fast my boat
goes also i am turning about 5000rpms.
i have a 150 horse NOS bottle that i havent put on yet im trying to hit about 90mph or better will this do it. thanks

[Jetmugg]

The most practical way to measure your speed is with a hand-held GPS unit. Beg, borrow, buy, or steal one. They are great. I'm not familiar with the Mako hull (i.e. is is a deep V, semi-V, flattie, or tunnel hull). As a comparison, my California Performance gullwing turns an A/B impeller at 5200 rpm's, and 77 mph on GPS. This is a pretty lightweight hull, with a professionally built Dominator pump, and about 450 horse 454.
SteveM.

[spectras only]

Travis, your Mako is a deep V fisherman style boat w/24 degree deadrise, yes/no?.You stated 700HP but no info on Impeller ie;"A" "AA". 700HP should turn more than 5000RPM, unless you running "AAA" imp.As Jettmug suggested a GPS would be your best bet.I have a maggelan model that's cheaper than a good Gaffrig unit and can be used anywhere including your car.Most people prefer the Garmin III that's sligthly more expensive.With the power you stated a 21 foot deep-V should run at least 60 MPH with a Berkeley "A" trim.Let us know your speed with a GPS.

[INFINITEJJ]

I THINK THE MAKO HE IS REFERING TO WAS MADE BY MIKE DONNEL. I BELEIVE HIS SHOP WAS IN SANTA ANA, CA. IN THE LATE 70'S. HE MADE SEVERAL KINDS OF BOATS INCLUDING DAYCRUISER'S, MINIDAY'S AND OTHERS. WITH 700 H.P. YOU SOULD PROBABLY BE TURNING ALOT MORE THAN 5000 RPM'S, NO MATTER WHAT IMPELLER YOUR RUNNING. WITH THAT KIND OF MOTOR YOUR MOST LIKELY NOT HITTING YOUR PEAK H.P. YOU SHOULD RUN AN "A/B" OR A "B" IMPELLER TO GET THE RPM"S UP.
[This message has been edited by INFINITEJJ (edited May 07, 2001).]

[Travis Petersen]

ok guys thanks for your replies i had a chance to get it in the water im am hiting 6200 rpm so for oh by the way i have a AA impeller , thanks again.

[spectras only]

Travis, sounds a lot better.I wonder how did you get 5000 readings before?, Your tach must have been out of calibration.Next ,get a GPS reading on speed,I'm curious what speed you're doing .