1997 31 Thunder Seems like it should be a little faster
 

Ok my first offshore boat,has 525sc engines 28p bravo 4 blade props, was able to get 74 mph on gps.
rpm maxed out at 5000 wot. Cool temps k tabs halfway down per indicator.2 people 1/2 tank lake was calm.
I was hoping for 80mph

https://www.facebook.com/photo.php?f...3831088&type=1

Indicators 1/2 way by gage?
But that doesn't say if that's up off the water or not.
Could be trimming enough to bury nose.
5000 RPM 28 pitch Bravo 1 blades is 88 mph theoretical.
With 16% slip is 74.
Flat water non step hull...
Sounds about right.
You may see 77-80 in --2' chop

Take a spirit level or straight edge off bottom of boat. Figure what ZERO trim is on drives and tabs.
Then trim from there.
ZERO trim is when the drive cavitation plate is parallel with bottom of boat.
ZERO tab is where the tabs are parallel with bottom of boat.
ZERO trim is NOT zero on indicators. Zero is fully tucked in ( nose down)
Zero tab is NOT zero on indicators. Zero is typically full up

I set my boat so 4 is zero on tabs and drives both.
That way if I'm running at 4 on drives I know that the props are pushing the boat flat and level. Not trying to lift bow up.
Tabs at 4, even with bottom of boat, are actually pushing the nose down because the water lifts slightly right behind the boat and the tabs are long enough to catch the rising water and drive bow down.

Were you possibly bumping the rev limiter? As I recall, could be wrong, the 525sc's had rev limiters at about 5050. Also, your boat would likely have better top end with 3 blades, such as Mirage Plus than you will get with 4s. I wouldnt expect to see 80, but if the engines are good (assuming stock making 490 hp), you could likely see close to that.

Have only owned the boat for a few weeks and is a big step up from my other boat a 1974 SRV180 165hp
The trim tab indicators set at 5 stop any porpoising but not sure of the angle in relation to hull.
Going to pull blowers @ 233 hours they have leaky rear rotor shaft seals and one front snout seal seems to fling oil off pulley. I'm sure in a 2-3' chop it would air out and pick up a few mph but to be able to say my boat does 80mph just sounds good lol.
All done for the season here water on st.clair is too cold to get in for me.

Sorry if I confused everyone trying to explain trim position.
Intent was (ZERO) neutral trim is when everything is set so it is parallel with bottom of boat. The indicators and their numbers are for reference only.

MichiMike I hope I didn't confuse you even more. Since your season is over for the most part....now is the time to set your boat up so you know where your trim is and get those 525SCs in top shape.
Good luck with your efforts.
And congratulations on the step up to the offshore family

No I get it.
Have not had any time to learn driving it. had to fix fuel sea pump oil leak (joke), circulation pump (easy)

Need to work on me being able to fit in engine room lmao

http://m.youtube.com/watch?v=yR5r2c5Bxpg same boat?

same boat