View Full Version : RPM/MPH Issue

11-08-2005, 08:16 PM
I am looking at buying a used Mastercraft and recently drove a 2002 Prostar 209 which has the 330 hp engine. It is my understanding that this boat should have a top-end of approx. 44-46 mph. The boat that I drove has the 13 x 13 O.J. prop which I believe is standard on this model.

When I attempted to get this boat to top end I could not get any more than 40 mph out of it. The RPM's would rev from approx. 4700 to approx. 5500 but the boat would not pick-up any speed. You could hear the engine producing more power but it never produced any additional speed. It almost seemed as though there was some cavitation as the prop spun.

Has anyone experienced this issue or have any ideas as to what the problem may be?

11-08-2005, 08:18 PM
Something is not right there. I wonder if the speedos are accurate? If you are pulling those kind of R's with a good prop on there than you should be getting more speed

11-08-2005, 08:24 PM
I'm not sure what the specs are for that engine but 5500 seems to reving pretty high.

11-08-2005, 08:32 PM
Thanks for your response. I have thought about the speedos not being accurate. However, while you could hear the engine produce more power the speedos never moved it never felt as though the boat changed speed. Additionally, it sounded/felt like the prop was simply spinning without moving water & that is when it seemed like there was some cavitation.

11-08-2005, 08:57 PM
Than their is something wrong with the boat or it doesn't have the stock prop and someone has put on a lower pitch prop. Check out the prop issue if its not that then I'd say something is wrong with the boat, maybe transmission related? Lack of trans fluid?

88 PS190
11-08-2005, 09:46 PM
Have you gone under and played w/ the prop checked to make sure the nut is tight, and the prop isn't damaged?

I personally like jrandol's theory about the trans fluid, could be generating a bit of slip and that is keeping it from going any faster, if you punch it it'll prolly slip then too, if the fluid is low.

(ask the owner to show you the trans fluid btw) He should know how to check, the color, be confident w/ the level, and know to warm up the tranny before checking. If he doesn't know these things its possible that the trans has been neglected. If fluid level is normal and clean w/o a dirty smell then the Trans is likely alright. Unless of course he is covering and changed it to hide something.

11-08-2005, 11:23 PM
Great advice on the possible issues! I did not think of the transmission fluid. I will work that angle to see if it solves the problem.

If anyone else has any thoughts I would greatly appreciate it!

Thanks Again!

11-09-2005, 12:30 AM
Great advice on the possible issues! I did not think of the transmission fluid. I will work that angle to see if it solves the problem.

If anyone else has any thoughts I would greatly appreciate it!

Thanks Again!

I agree with LLSkier At wide open throttle 5500 RPM's is too much ... here is a link to waterski mag's online review of the boat (http://www.waterskimag.com/product.jsp?ID=61547&product=boat&clientID=17146) it does look like the 4 blade 13 X 13 was standard (with the 310 hp engine), what elevation are you at? They list 43.8 mph at 4650 rpms for the 5.7L 310 hp Predator in the "Full Review" (http://www.waterskimag.com/article.jsp?ID=3009) of the boat ... so it would make sence for you to get more, not less, with the extra hp of the LTR 330hp engine. The following is the review of the LTR330 on the 2002 Sammy Duvall 209 (http://www.waterskimag.com/product.jsp?ID=61548) so it should give you a comparison of how that engine ran new, and here is the full review (http://www.waterskimag.com/article.jsp?ID=3007) where it lists ... edit check out the prop size on the Sammy Duvall (same engine as the one you are testing) while the sammy had powerslot (larger prop diameter and pitch than the standard 310 hp), the WOT RPM's should be the same, making 5500 seem high.

Length 20 ft. 11.5 in.
Beam 96 in.
Seating Capacity 12
Fuel Capacity 35 gal.
Test Prop OJ 14 x 18 4-blade
Test Engine Indmar Vortec LTR 5.7L MPI, 330 HP PowerSlotTOP SPEED 45.8 mph 5,200 rpm
ACCEL. TO 30 4.7 SEC. 115.0 FT.
ACCEL. TO 36 6.2 SEC. 189.93 FT.
Neutral 60 D 60 R
36 MPH 90 D 92 R

Does the boat you are testing have powerslot? Also, anyone else out there in MC world confirm that he has the right stock prop for that engine? Just my 3 cents. Casey

11-09-2005, 06:37 AM
I would suggest having the propeller looked at. A damaged or poorly reparied propeller, cup removed in the repair process, could be the problem with the RPM/MPH.