Boat seems to be missing 10 mph and 700 rpm

[Striper80]

I have a 99 wellcraft 22WA with a 98 Johnson 200 2 stroke on it. The boat is running the factory prop that I had redone. The factory claims this combo is good for 50 mph at 5800rpm, which I figure is quite generous. Right now at WOT I get 5100rpm at 28.3 knots. I'm not sure where to find those extra rpms. The prop is a raker 14 1/2 x 18 I've owned the boat for about 4 years now and it's been this way since. Compression is dead even 100 across the board, which I thought was low, but I'm told is good. My 130 Johnson had 150 on each cylinder with the same gauge. Did the carbs last year and link and sync, same. Throttle seems to be opening all the way as well. Ohmed out all the coils and checked timing on land. The bottom has bottom paint and it's king of rough, no growth though. The lower unit is an sei and it's supposed to be the right one for my application.

[Destroyer]

I am NOT an expert on these things.... I'll leave that to TheFermanator and SpareParts. However, having just said that, it sounds to me like something is drastically wrong. A 200HP engine should be producing a lot more than 29 MPH at 5100 RPM IMHO. So I'd be looking at two things.

1) You said the lower is a replacement. What does the factory call for as a final ratio, and what is your lower producing?

2) Is your prop an original Raker or a Raker II? The Raker II's have a lot more cup in them for the same pitch and dia. and that could account for a lot of your lost RPM. So (and I know this is just a guess, nothing more) if the reworked prop was worked to Raker II specs and your original prop was an original Raker then they added more cup to the prop and that would account for your loss of RPM.

Use this link to calculate: http://www.rbbi.com/folders/prop/propcalc.htm

[Striper80]

It's the original prop to the boat. Atlantic propeller in Edison did the work. I didn't really pay attention to how it was before I had it done. I ran the boat only twice before I had the prop done. The PO actually hit something that knocked the tab off the lower and put a small nick in the prop. The lower was under warranty and I sent the prop out.

[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.