2001 owners inside prop question

The boat I purchased (86 nautique 2001) has a acme 542 prop, w/ 3/4 tank of gas and 3 people the boat tops out at 36.x mph at about 4100-4200rpm is that normal? I don't care about top speed I just want to make sure thats normal and b/c of the prop. Second of all if I go wide open throttle straight for a minute or so it starts to surge then come back just a tiny bit, and I slow down to around 35.5. I'm sure the surging is probably fuel related, bowl adjustment or something simple. Since it only happens at WOT when going across the lake, I'm just not gonna worry about it b/c I shouldn't be taching those rpm's that long anyways. My main thing is just making sure the top speed sounds normal. Confused EDIT: Speed is read of perfect pass. Paddle wheel not gps.

It probably is 4300, I should've looked at the Perfect pass RPM's. I don't know why I looked at the factory gauge. I just wanted to make sure the speed sounded right. Boat has full tune up and electronic ignition which is why I think it's fuel related.

Joe my definition of close may be conservative but assuming a 2001 hull with a 540 is good for 43-45mph at 4500rpm. I would have thought a 542 would max out 39-42mph. So i thought 36.X was about right for 4100rpm.

Warning....thread jack. Joe I was only thinking the other day how you were going on your SN196 GT40 project boat.

Joe, the 2001's Ive been in with the 540 turn it nearly exactly 4400 per the tach and 45mph on the GPS. Id say 100-200 more RPM for a 542, and maybe a mph slower on top?

36mph @ 4200 is way off indeed.

Did compression test, motor at temp, all plates open on carb, all plugs out and read as follows

111 120 129 130 115 111 125 125 according to everything I've read the motor is healthy. I wonder if something is stopping me from actually hitting wide open throttle... perfect pass or something... when I go WOT my throttle lever is just above being level to the boat side. Most boats I've been in go past that or at least totally level. hmmm

Yeah it is too much to be a compression type issue, ignition advance or lack thereof perhaps, but more likely carb or as you mention throttle position related. If you are worried about your throttle position take off the arrestor and with the boat in the on position but not running (required due to the perfect pass) look at the butterflys to make sure they are both fully open (perfectly straigth up and down). If not remove the throttle linkage from the carb and actuate it by hand and see if you can get the butterflys open all the way by that method.   

Yeah I am slow today.. too much time with mechanical secondary carbs in the last couple weeks.. vacuum secondaries wont open when not running, but your not going to want to see that while running too dangerous. You should see the primary actuate the entire way and at that point be able to make sure the secondary moves freely and easily to all the way open while sitting there with the motor off..

I have an 85' w/ 542 slight ding in the prop and I am running about the same 4300 @40 mph I think I have a bad power valve my compression is about the same

Did you ever check if you actually get full throttle from the carb?

I certainly would not worry about how for the throttle lever goes compared to others. But if you get more throttle from disconnecting the throttle cable and opening the throttle by hand, then there is definitely a culprit.

Rebuilding the carb would be a good idea if it has not been done in a while.

Buy a marine carb rebuild kit, as you will have non externally adjustable floats unlike cars that have externally adjustable floats.

Also, find out what power valve you have in it. A 6.5 should probably be your best bet. It's possible the secondaries are not kicking in, or that the floats are mis-adjusted.

I've been running an Acme 208 4 blade, so I can't comment about the 540 vs 542. My hull is a little different than yours too.

I might pick up a 540 though to see if there's any difference between the 208 and 540. I'm certain there will be a difference as the 540 is a lower pitch by .5, just like the 542 is .5 less pitch than the 540..