OK guys, I have a 97 Skeeter ZX202c with 200 hp Yamaha pro-V, when I first got the boat it had a turbo lightning 24 but prop had some dings, and it ran about 65. I switched the prop to a yamaha 25m, speed still the same at 65, and since prop was nice and new I kept it on there.
Over past 2 years, I've replaced the spark plugs and re-sealed lower unit but nothing else to motor. While I was putting new spark plugs in I lost the bolts for my airbox so I just left the airbox off and put the cowling on. This was around the same time I lowered my jackplate about .50". next time out I saw a loss of a couple mph , and during this same trip the motor started bogging down a bit, even dying, when trying to take off - but it started doing this halfway thru the trip, after a full fuel-up. It would hesitate around 2000 rpm especially if I had another person in the boat, I would have to hold the throttle at 2000 rpm before pushing the boat over on plane. Once on plane, it got up to 5800 rpm and 62-63 mph just fine. Not 65 @ 5950 rpm like when I first got it. Now this year I am only getting 60 mph and only getting 5700 rpm with two people and very little gas in the boat and it is still bogging down a lot, pretty much every time I take off.

I have read that in some outboards, the airbox is important for fuel/air mixture, but I don't know if that's the case for my carbed 200 pro-V. Also, speed has decreased since I've had the airbox off so I have a hard time beliving that is the cause of the loss in speed.

My RPM's are still 5700, and when I first got the boat 5700 rpm was nearly 63-64 mph,so it seems like with my RPM's staying almost the same, I'm losing top end. There are no nicks on my 25m prop. I can't figure out what could cause this.

Is there some sort of engine maintenence that I could be due for that would be keeping top-end RPM close to normal while causing a loss of speed and issues at hole-shot? my water pressure is fine, I don't know exact number but it's over halfway on the gauge (I Think 18-20)

thanks in advance and sorry for long post, I am relatively new to bass boat set-ups..

Put your airbox back on. For a carbed engine it can change the fuel air mixture.
Why did you lower the motor half an inch? That can affect top end speeds for sure.
If that does not give you back speed you may have some added weight. More burgers? Fishing tackle? Water in the hull?

Don't forget the gas today won't produce same energy with the moonshine in it.
All boats slow down some over time. Probably you car does too but you aren't running it WFO down the road every time you jump in it either.

The boat is a 97 and ran 65-66 consistently for years, but in 8 months it drops 5-6 mph?

I lowered the jackplate because the steering was a bit stiff and I Was just experimenting. I'll raise it back up and install the airbox and see if it works better, I sure hope the hole shot stall is fixed, I can deal with only going 60 mph for now.

Seems like same rpm with same prop would rule out motor, if prop is good then it could be more weight in boat, distribution of weight or could be the hull itself has developed a set detrimental to the top speed. Check the bottom for waviness or roughness at the rear of the boat....waxing it helps top speed.....and put the jackplate back where it was. The prop might look ok but could need to be trued up, a little out of balance can make a big difference.

Just reread post....could also be fuel lines/filters, ethanol is hell on the old rubber fuel lines....also check the primer bulb to make sure it isn't collapsing at WOT, that would be a sign of starving for fuel.

I run seafoam every other tank and am pretty sure I haven't put ethanol through it. Would a fuel line/filter cause the issue getting on plane?

I am going to raise my jackplate a little more just trying not to over do it since going down is the hard part.

Any gas station is 10% moonshine today. Can't escape it.

Bronco, never wax the hull. Does not help speed

Thanks, looks like that is an old wives tale! Now I don't feel so bad about not crawling under mine and waxing it

We have non "moonshine " here at Fork, it may set you back a few pennies but it's worth it in the long run , I run in the boat and lawn equipment

Not to hijack, but I was about to post a similar question. I recently bought a 2007 Ranger Z20 with a Yamaha 225 HPDI. 140 hours on the motor with lots of idling. Compression test when I bought it showed 125. The speedometer doesn't work and I just got a Humminbird Helix that shows my max speed with the hot foot all the way down around 50mph. Top RPM is just under 5000. I don't know the specs of the prop. And this is with playing with the jack plate and trim. This is with me riding alone. I hear everyone talking about 60+mph and wonder if I should be expecting the same?

Yes. Something is definitely wrong. First thing`s I check when trying to diagnose this problem: throttle cable or hot foot adjustment, fuel restriction, motor performance (carbon build up, sparkplugs, coils), prop problems, then boat hull problems, water trapped the in hull, warped boat pad or too much equipment in the boat. Last could be driver error.

As mentioned, "water trapped in the hull" was definitely my problem, found a hill and drained out more than a few gallons!!!

Great info, thanks. Can anyone recommend someone in the Fort Worth area to investigate this?

Has this boat always performed like this since you bought it? How is the holeshot? If it has run like this and the holeshot is poor I would definetly find the numbers on the prop to get the pitch, could just be badly overpropped....I believe that motor should be 5800 - 6000 WOT.