Boat seems to be missing 10 mph and 700 rpm

[THEFERMANATOR]

Ok, you say 28.3 knots, so thats 32.5 MPH at 5100 RPM's comes out to 30% prop slip, that's BAD! My 1st question is, has this prop always ran this way or is it only since being reworked? I've had more than a few props ruined after having been rebuilt by a prop shop. I'm close to one of the largest in Florida, and they've screwed up several of my props to the point they never ran right again, but looked perfect. The V-6 engines will ALWAYS have less cranking compression than the V-4's. Reason #1 is 88+ have idle reliefs to cut low RPM compression to make the engines run smoother. And reason #2 is the starter. V-4's have a direct drive starter whereas V-6's use a gear reduction, so V-4's spin over a good bit quicker.

As to you issue, an 18 pitch on a 200 JOHNNYRUDE is ALOT of prop for a 22 footer. I spun a 17 pitch on my 20 footer, but really should have had a 16 on it. I would be looking very HARD at your current prop in areas like cupping and rake for your lost performance. Alot of times prop shops don't have the correct block for a particuliar prop, so they use one thats close that they have on hand, and when they alter the blade design, it ruins the props performance. I had a little 3 blade stainless on a 25HP SUZUKI that looked like trash, but the engine spun up to around 5600, and the boat would hit 33 before it started chine walking so bad I let out of it. Had the prop rebuilt hoping it would help the chine walk, after rebuild the boat would only hit 26MPH(could run 29-30 with a cheap 4 blade aluminum), and barely spin up to 4500 RPM's. Experienced similiar results with several others, but put on brand new props and the performance came back.

In all honesty though, I would think a 22 footer with a 200 JOHNNYRUDE would do well with a 15-16 pitch in a fairly good biting prop. I have a STILLETO prop out in the shed that would probably run well for you, but you're a bit to far away to just let try it out, and shipping would probably be $40-50 through UPS.

[Striper80]

I have a 14 1/4 x 17, I'm pretty sure these are the numbers, apollo prop in my garage. Maybe I'll throw it on just to see. I bought this boat used about 3 years ago and I've only put about 40 hours on it. When I got it the GPS didn't have a speedometer on it so I didn't notice how fast I was going. After two trips I put it away for the winter. Over the winter I had the prop done because the PO nicked the prop. I also got the sei replaced under warranty, did the control cables, and installed the current GPS. My seat of the pants feel was about the same, but it was a bit skewed since I had to do the whole sei break in.
Last year I did the carbs, link and sync, and set the timing, cranking method since I have no test wheel. I had an issue with stalling going from idle to part throttle after that, but I seem have that handled after changing my water separator housing and draining the whole gas tank.
I hadn't thought about prop slip. I was only thinking that changing the prop would change rpm but not overall top speed. Since owning this boat I've always felt that it had less punch than my Striper 2100 WA. That boat was 21 from pulpit to stern and this one is 23, but that boat only had the 130 on it.

[THEFERMANATOR]

By all means try the other prop. Something is definately off with 30% prop slip. That is HUGE for prop slippage at 5100 RPM's. The stilleto I have is a good biting prop that actually has very low prop slippage, and good top end kick. Definately try another prop though, something just doesn't sound right with yours, and you never know if they used the wrong prop block when they redid yours, and messed up the rake when they reworked it. Adding cup would bring your prop slip way down, but it normally costs you top end speed, and you're already turning way to low at WOT(should be seeing 5400-5800 RPM's on that engine to keep it happy, and live a long life).

[Striper80]

Swapped the prop today and saw a best of 31.1 knots at 5100 rpm. Boat was cruising at 28 knots easily at like 4200. Not sure why it won't go any higher. My stalling issue resurfaced though. I think either the pickup is restricted or the pump is failing. The ball gets soft but will get hard when you pump it.

[Destroyer]

Have you done a compression test of the engine after it was warm? If we presume that it's getting the proper amount of fuel and air then compression and timing are the only two things left on the engine that could be effecting the power. Also, you still haven't done a lower final drive ratio test. And what spark plugs are you using?

[THEFERMANATOR]

I think you need to try another tach 1st. 31 knots at 5100 is still pretty high prop slip at 18%. You could easily have a bad tach throwing off your calculations.

[Striper80]

Originally Posted by Destroyer

Have you done a compression test of the engine after it was warm? If we presume that it's getting the proper amount of fuel and air then compression and timing are the only two things left on the engine that could be effecting the power. Also, you still haven't done a lower final drive ratio test. And what spark plugs are you using?

Yes, compression is good and the plugs are correct. The timing may be off as I don't have a test wheel so I set it cranking. Assuming the tach is correct, which I've been questioning, the idle is too high so the timing is off. The boat is idling at 1000 rpm.

[THEFERMANATOR]

You CANNOT set the timing cranking the engine over. There is spark advance built into the ignition module that starts ramping up around 3000 RPM's till 5000 RPM's. The other problem is there is a 6 degree timing advance during cranking until the engine has run for 5 seconds and has reached roughly 120 degrees. You do not need a test wheel to set timing. If you can get it up to 4500 or so on a trailer, that is ALOT better than setting cranking. Not setting the timing right is a GUARANTEED way to burn that engine up. It calls for 18 degrees, if you go over 19.5 degrees, it WILL melt a piston. Even so much as 19 degrees is playing with fire. Most who set these engines up set them to 17-18 at 6000 RPM's. you're better at 17 degrees than 19 degrees. But if you set it to low, it will foul out, carbon the rings up, then you'll stick a ring, and BYE BYE cylinder(some ran at 14 degrees, but they were jetted for it, had MONSTER carbs on them, and were meant to run at 5000+ for sustained periods of time). Get your timing set correctly before you go any furthur unless you want to be buying a new engine. You're playing with fire, and it WILL burn you here.