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deejay
06-28-2010, 12:00 PM
I have a new (now ~50 hrs ) Marine Power 454 330 hp in a 95 22c swinging a new Mirage Plus 23 thru a Bravo One drive and I have questions. Please make comments and suggestions on the following: Idle in gear is 650 to 750 RPM at 4 mph G.P.S. WOT is ~4,000 RPM at 51 mph with slight surging at WOT. At 30 mph to 40 mph when I punch the throttle to wide open the boat feels like it is going to leap right out of the water but it tops out at only 4,000 rpm. From what I feel I have seen on this incredible list, the 23 prop seems like it should be the correct prop, maybe with a little touch-up from Throttle-up or Bblades. Is that correct? Does the surging at WOT throttle indicate a lean fuel mixture? Does the Mirage Plus 23 seem to be the best prop for this setup? I feel like I should be turning 4,300 to 4,600 RPM and in the low 60s mph. I run the boat at natural trim and no tabs. What are your thoughts? And another question - what is the max out of gear idle RPM that it is safe to shift into gear? The boat runs stable and true - like it is on railroad tracks at all speeds. The only thing I feel I have to be alert to is if the throttle is chopped while at elevated speed. In that situation the boat rolls to stbd but I feel that is to be expected given the boat beam and the sudden change in engine torque. My wife and I love this boat but you can see from the above that I feel there is something not quite right with the engine/prop size/speed performance. We are looking forward to your input. Thanks, deejay

BigGrizzly
06-28-2010, 03:57 PM
Your trim is too low. That engine should swing that prop at 4800rpms. If it is surging something is wrong.

HOWARD O
06-28-2010, 04:40 PM
Grizz is correct of course, you should be able to get to 4800. While my boat is different in that I have a TRS drive instead of a Bravo, I just recently went 63 mph GPS swinging a 24 pitch Turbo 1 prop. This is with the old, original 330 horse 454. I'd say your boat should be faster than mine if not at least as fast..

When you say that when you cut the throttle, it'll fall drastically to one side further indicates to me that you're trim is too low, as Grizzly states. If you are able to get that bow more up and out of the water and cut the throttle, it is less apt to fall off to one side because you have less hull in the water and it's running more on the rounded part of the keel in the back. At least that's been my experience. I would also say that when I am trimmed out and running past 50 mph, it doesn't really feel like it's on rails like it would at slower speeds because it's running on the rear. It'll feel a little more loose and "aired out", so to speak. I'd say go out and experiment more with your trim. What I did was get it up to around 4 grand, going straight. Watch that GPS as you start to trim that outdrive up and watch the speed go higher! I was surprised how far I needed to trim it to get that bow riding up higher.

I learned all of this here and I hope this helps....folks with more experience with the 22 will surely chime in!

deejay
06-29-2010, 09:23 AM
Thanks BigGrizz and Howard. I have to admit that I have done very little experimenting with the trim. I will be giving that a try as soon as possible. Howard, I am glad you mentioned about being surprised how far you needed to trim out. I can easily see how I would have backed off - thinking I was trimming too far. It will be interesting to see how that affects the speed/RPM. I assume surging at WOT will still present a problem. Could that well be too lean a fuel mixture? Howard, your fuel flow posts last year mentioned jet size. Do you happen to remember the size and effect from changing, and could that be a key? Thanks Again, deejay

CaribouLou
06-29-2010, 09:30 AM
I don't run a trim gauge, I just feel the boat....it takes seat time to really get these things down....not just a boat you can hop in and drive.

DamnDonzi22
07-03-2010, 10:31 PM
Most likely the surging is being caused by lack of fuel. I had same issue on a '87 22c and finally rebuilt the carb and reset the float level. Alls good now.

tmh
07-04-2010, 08:52 AM
Start at the beginning for the surging and make sure the spark plugs are good as well as the cap and rotor. I had some surging and reduced RPM's 2 weeks ago and a fresh set of plugs really helped when we went out on Friday. The old plugs looked very nice as to color but the gap had become immense.
T.M. Hayes

deejay
07-06-2010, 04:47 PM
Thanks for the suggestions DD22 and tmh. The plugs are new NGK with about 20 hrs on them but I will take a look at them. The carb is a Holly that was completely disassembled and inspected. Fuel filters are new. Have used nothing but non-ethanol gas. I am getting the feeling this all needs to be gone thru again with special attention to the carb. I notice that no-one suggests that the boat is over propped. I am getting strong direction from a local technician that the prop is too much. From this list there seems to be a definite feeling that a Mirage Plus 23 is just about the correct prop. Thoughts please. Have not been able to get out to play with the trim. Thanks Again, deejay

oledawg
07-06-2010, 05:29 PM
My 22C has a few mods, more cam, edelbrock high rise manifold, holly 850 double pumper, etc. so it is cranking right at 400 hp, but here are my thoughts:

- I tried a 23P and while it spins about 600 rpm more than the 27P Mirage that I normally run the boat was just not as stable at WOT
- the 27P works best for me, pulls right up to 4,800 rpms and has incredible acceleration from 3,000 rpm up.
- I run with trim tabs full up
- at WOT the outdrive trim is just below the mid mark, it is trimmed up pretty durn well
- yes, from WOT I ease off the throttle to minimize the "roll to the right" effect while at the same time reducing outdrive trim and dropping the trim tabs
- depending on water chop I can easily get 65 and if life is good and I am feeling my oats I can squeeze 70 out of the old girl....:wink:

These boats are like motorcycles in that when you are running hard you best be paying attention and have some seat time so that you know the "feel" since as Howard O said " the only thing really in the water is the outdrive and the rear edge of the keel"......small corrections as needed to the wheel and just keep the hammer down......but nothing stupid :cool!:


http://www.youtube.com/watch?v=JyhUDgLb9TU

http://www.youtube.com/watch?v=vbzMaZg4OJo

austinmark
07-06-2010, 05:42 PM
I took delivery of a 1987 20' DONZI Minx Limited Edition (#21 of 25) last week...something I've wanted for some 20+ yrs. or so. Splashed it Sunday and all appears to run fine, however the pitot was busted so speeds are a guess at this point. 3000-3400 felt like a natural cruise speed (40-45mph?) & once out of the wakeboard boat wakes we ran +/-4000 & felt aired out & a little skittish...trim @ 1/4 out & slight port tab to level things up a bit. Fairly normal experience? Not quite settled in with a smaller low profile rig just yet!

350 Mag/Alpha 1, 23 Mirage, standard Bennett tabs. I replaced plugs w/ NKG BR6FS @ .040", MSD wires, MSD Master Blaster coil, new cap & rotor, Amsoil 25-40, Merc oil filter, K & N air filter and Merc High perf gear lube on Saturday before running Sunday. I've ordered a Blackfin Skeg guard to heal up prior skeg damage...anyone have experience with one of these?

Hull sides are black & buffed out pretty good, the deck gel coat is shot & will be redone this winter...Imron or re gel coat...any advice?? Previous owner obtained new bucket seats and rear pads from DONZI last year & never installed (nice to have)...not Limited Edition charcoal w/ red, but much more desireable to me in white w/ black piping & I'm not concerned with being a purist...just after a nice, clean, solid small boat for a small lake (river actually) Lake Austin, here in Austin, TX. as I keep a big criuser on Lake Travis.

Current rigs...1987 20' DONZI Minx
1989 34' Sea Ray Sundancer (2x454 Mag)
Previous rigs...1988 22' Sea Ray Panchanga (454 Mag)Great fun!
1997 32' Fountain (2x502 Mag FFI)
2002 29' FORMULA Fastech (2x377 HO EFI)

I enjoy reading & learning things DONZI here...thanks for any input on this project.

austinmark :cool!:

22times2
07-06-2010, 05:57 PM
trim that baby till you notice a increase in rpm and cavatation then bring the drive back down slightly till rpm decreases then you should be right where you need to be,the sweet spot you will need to prop according to where your rpms are good luck.mike:wink:

oledawg
07-06-2010, 06:05 PM
Good answer Mike :nilly:

BigGrizzly
07-06-2010, 08:59 PM
Now my origional 330 with a TRS drive turned a 23 at just 5000 at 63 MPH and that is what you should be doing.