danedee

thanks everyone!

I'm having the marina drop the boat in the water today, i'll ask them to check drive ratio and prop size before they drop it. And i'll find out where exactly i'm at on the tach too. once i have that info, i'll post back here and hopefully some of you can make sense of all of it and (hopefully) some of you will tell me that i AM in fact running a totally wrong prop and recommend where/what to purchase to get speeds in the 68+ range again.

thanks again in advance!

danedee

ok, so.... 1.68 is the drive ratio.... is that one of the numbers we are looking for?

and the prop is a bravo 28p

I also looked in my fountain bag of tricks and found the test sheet showing the results from the factory tests, and it ran 69mph at 5150 when she was new in 05, with the 28p bravo prop. Now i'm running 59mph with the exact same setup, at WOT, (5125- bouncing up to 5175 maybe in the chop, but mostly holding right at 5150).

So.... everyone here is sayin i should be runnin high sixties.... anyone have any ideas? if i DO change props, won't essentially be changing the final 'gear' so to speak, and lose RPM?

danedee

Anyone have any input? Bump.

Griswald

10mph? Ouch........

I tend to lean on something else being the issue with that big of a drop in speed.

Wildman_grafix

Are you sure your tach and speedo is right?

I assume the speed is GPS so maybe the tach is off?

The test sheet will also show trim and tab settings, plus what drive ratio.

danedee

Tabs up, trimmed to almost five, yes verified on gps. Test sheet said 1.68 drive ratio, that's where I got the numbers, ok yes something else ( not prop I guess) is wrong, but what is it and how to fix it ? Lol

Von Bongo

I take it this is a new boat to you and you didn't just lose 10 MPH over the winter.

So did you take the drive ratio off the sheet or actually verify it? Did you take the prop and compare it to a stock 28 bravo 1? not to sound stupid but it is a 05 hull with a single step and a bravo 1 drive and a 4 blade prop right?

A couple of other thoughts. Drive isn't what is thought. Prop is marked 28 but has been modified, cut down, difuser ring added or removed or is marked wrong or all of the above. your RPMS are not what you are seeing or your prop slip is through the roof. Is you GPS set to knots and not MPH? 59 KTS is about 68 MPH.

Some numbers with a 1.65 and a 4 blade 28 prop you'd be at 68 MPH with 15% slip. that's physics, if you do have a 28 stock prop, you are turning 5000 RPMS and your slip isn't throught the roof you are running 68-69MPH unless you forgot to unhook your trailer.

Make that prop a 24 and you are 59 mph. Or same scenario if you only turn 4500 RPMS with a 28 your back to 61 mph. I would doubt an unhealthy engine will turn a 28 prop to 5100 rpms.

Also are your drive and tab indicators correct. You should ignore them run the tabs all the way up to the stops and run the drive trim by feel. out until you feel the prop start to slip and you would also start to see a drop off in speed, then trim in small fractions to get top speed.

take a 2nd GPS to verify. borrow a stock 28 bravo 1 prop and run it. I still think you prop isnt' what you think, the drive isn't or your RPMS are not accurate.

Boat would lose about 1MPH per 100-150 pounds of weight added but as you add weight your max RPMS would decrease. If you have a huge hook in the hull I suppose it's possible but again I don't think you would be able to hit 5000 RPMS.

danedee

thanks von bong,

for the insight.... i just checked the digital camera we had with us this past weekend, and verified that no, we didn't have the trailer still attached.... no fishhooks on the boat either. i'm beginning to suspect (with what little intellect i have) that it's a prop issue...

I'm going to have the marina throw a new bravo 28 (loaner) on the boat for me before they put it in the water, and see if that changes any numbers for me.... (if it does, than mine is getting sent to BBlades for conditioning/labbing) if it does nothing... .then.... hmmm i dunno...sell the boat and buy a four winns?! lol (just kidding, i'd never do that!)

carcommander

I have the exact same boat as you. An 05 with 70hrs on it. Mine ran 67 yesturday, full tank of gas just me in it. Tabs at 2.8 Raising them further didin't matter and drive at 4.9. This is on a fresh water lake with a light chop. 5100 rpm. Stock X drive and stock 28P prop. If you are only getting 60 something is up.

SDFever

Don't forget that you're asssuming a "strong" engine. If nothing has happened to the prop then the power went somewhere.

Where did it go? Five years have passed and that can mean a lot to any engine... If NOTHING on the boat has changed then you have the same test sheet I have. No offense but you are starting at the "end" instead of the "beginning". Something does not add up to only be the prop (unless it's a modified prop).