So new boat...22' 3850lbs..454 330hp...1.47 drive 21degree's..low hour motor..400

First run 19p merc mirage 5000rpm..50mph...1.47 gearing ran up to 5000 and the engine ran out breath.

Second run 21p black max (alum) 5000 rpm 51mph...big slip numbers..25%?

What's acceptable slip and a boat of that nature....Do 454's fall that easy at high rpm....Yes its a alpha one drive..or copy,,SEI. I really have a urge to jump to a 23 TXP turbo no four blades this drive is dancing on glas the way it is. any suggestion's?

the 454 330 is done at 4800. You need to step up to at least a 23. Im getting ready to try a 24 bravo 1 4 blade, 22 foot boat, 24 degree same motor.

The 330 hp MerCruiser is cammed to turn 4200-4600 rpm. Yes, it does run out at 4800 rpm. In later years the rev limit was set at 4750rpm for that very reason. I would try a 23" Mirage Plus. That should turn 4400-4600 rpm and give you about 56-58 mph.

Thom

So ive made a selection a Turbo txp ot4 23 4 blade very much a laser like prop with high rake and a small diameter and larger blade area read easy on the drive and bow lift. However I need a exhaust ring are those avaible I don't know the exact diameter of the barrel.

Hopefully I will get 60 out of the old tub..but I am a bit concerned about the prop barrel matching up to the drive housing..The boat does have thourgh the hull exhaust.

So a little update The turbo fxp OT-4 is probably not a prop for a stern drive. It did not match to the barrel of the drive almost 1/'4" gap between the prop barrel and the drive. It is however a prop with lots of bite, the boat turned to 4000 rpm and 54mph gps with the 1.47 drive that's about 8% slip.As you can see the numbers are all over the place..i have my work cut out for me verifying the tach.... fuel supply system...and timing, She's a old girl but handle's very well..time and money i beleive 60 mph is obtainable...Right now this engine seems very sluggish..i have a 4.3 in a 3000lb bow rider that winds up's twice as fast..it really takes time for this old girl to build up steam.

Purchased 86 mirage 217 intruder 2 years ago, I want to post pics of the updates but I have to have 10 posts on this site before they will let me. Stock boat went 51mph gps and now 70mph gps. Hope to get some conversations going so I can start posting some pics

217 now has 496

makes 525hp

In 1990 I bought an all black mirage 217 intruder with bravo 330 set up.

The top speed of that 1990 330 hp was 61 to 62 on the speedo, gps was unheard of.