My neighboor has your boat, although I believe it is an '89. There is no step and I think it is equivalent to the new 35 without the swim platform. The 454's say 420 hp on the outdrives (or is it 415). Running Mirage (3 blade) propellors, it runs 72 on the speedo. If it doesn't run 72 he retunes, rejets the carbs etc. until it does. When his props were stolen last year he replaced them with 4 blade propellors and the boat lost 4-5mph. He then switched back to the Mirages.
Hope this helps.

According to my calculator, 4800 w/23's , assuming 1:1.5 ratio is 69.69 before you subtract for slip. 69.69 x .90 would give you around 62-64 mph. What is the ratio of your TRS' ??

I would guess that you should be closer to 72.

I'll look at the drives this afternoon, will it say on the drive what ratio they are?

It was about 4800, one wanted to pull a little more to about 5100, then we found that one of the cables wasn't letting the slower motor get full throttle!?!?

I'll also double check the props this afternoon!

I just checked the props!! They are 25p mirage's and I didn't see anything that said 1.5 or 1.36, I did see a
serial # OC954495

I do have a set of 23p mirage's though, should I try them? I really didn't want to pull anymore RPM's. Could I have them worked over?

What is the operating RPM of your motors? If it is near 5000, you better stay with the 25's. When you retest with the other motor wide open you will most likely see a noticable increase in speed and a little bit more rpms fron the other motor. I don't have a calc in front of me now, but you should be a little faster turning those 25' at those rpm's.
put these number into your calc:
5000/ratio(ex 1.5)=a
a x 60 = rpm's per hour (b)
b x 25" props=c
c/12=d (feet per hour)
d/5280 = Theoritcal speed
multiply that number by a slip factor, say 10% or .90

You should be within a mile or two. Verify with your GPS.

Brad loss a couple of cases of beads and the boat would run faster.:) If you want to try some props give me a call. I will be at lake shores most of the weekend and Jason has several props you can try.

Funhome,
My information says that a 1988 420 TRS is rated at 4800-5200 RPM. Gear ratios are the choice between 1.1, 1.25, 1.33, 1.5, 1.58, 1.60.
One of these numbers will be on a sticker on the side of the drive or stamped into the upper housing.
E-mail me for phone # if you need more information.