Having read all of this I was a little confused.

I have a 1991 30SS with 7.4’s that has always shown 74 plus on the Speedo. This year I found out that that respectful 74 is actually a reasonable 65.7 on GPS. I am sad to admit that after 11 seasons I dropped a valve and I’m in the process of a rebuild.

My point is that stock eleven year old 7.4s are running 65.7 on the Chesapeake Bay. I’m sure you can imagine the amount of clutter one gathers over 11 seasons in the cabin. She’s not real light.

I feel real good about the speed and overall performance of the Irish Mist after all these years. I had a friend with a 30 SS with blown 850+ (he would never tell me exactly what) that wouldn’t go over 92. Jay told him that that was all the hull was capable of.

CelticPride - maybe you should try some different props. I had my 35 with the same power up to 67.1 on GPS with 25P 3 blades and 66.7 with 24P 4 blade hydros. (in fresh water) I have been told that the Bravos are for bow lift and the Hydros are for stern lift. Maybe you need Hydros. If you can borrow some different props, I don't see why you couldn't break 70 mph.

HTH

BN...dailing in 4.5 mph from prop is not a reasonalble goal with his set up....and as dano stated; diferent prop for diferent conditions...people most of the time only look at the top end number as a referance for an increase in performance....while all too often they have slashed their cuising speed by 5 mph and cruising MPG just went to ****!...this is where the poeple that REALLY know what there are doing are seperated from the ones that think they do.....example....my top end props are 2 mph fast and accelerate like there is no tomorrow over my cruising ones....my cruising props are 8 mph faster at 4000 rpms and my fuel economy is amazing!

BN, I actually am no that concerned with what I get for a top end. The boat runs excellent the way it is and I spend most of my time int he 3400 to 3600 rpm range anyway.

Have any luck sellng your boat? I am trying to sell mine as I may be forced to move back north forjob reasons.

audacity - I realize that there are more things to consider than top end. I was just giving honest results in real world conditions. I opted to run the 4-blades all summer because the boat planed better, was more efficient etc. But of course I had to gps them at top end.


CelticPride - no luck yet. It's winter up here so I'm going to have to find someone down your way to buy it. I'll make a winter special if you know anyone.

shhhhh.....i find myself hitting the recall toggle to see what we ran too sometimes

Irish Mist,

Sharp lookin' boat! I guess you found out that a GPS can really hurt the ol' ego. Are the 7.4's the 330hp engines? 65.7mph is still pretty good.

Dyno/Don,

When you're doing a water test next spring I will go out in my boat and we'll both run along side each other and compare the numbers on each of our GPS's. That way maybe we can narrow some of this stuff down a little better. Can you believe that I'll actually have my boat running for the spring? Who knows---maybe your boat will out run mine!-----then we'll ALL really be scratchin' our heads!

Dyno's 31SS with 330 engines ran 65 mph on my Garmin GPS 95 on the prepurchase sea-trial. We did two runs, one upwind at 66 mph, one downwind at 64. After the engine upgrades the boat ran 75 mph on my GPS. You can say and think what you want but this boat ran the 75 Dyno said it did. Personally I think his tachs are reading 200-300 on the low side.

ok then...for your sake please look at the math...the boat had an engine upgrade, used the same props and got 10mph?...by the way do the math with 400 rpm added for error on the tachs...so both tachs have the same error??