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84exciter
07-13-2001, 04:55 PM
ok,here's the problem.took a old jackplate off the checkmate this year(1.75" setback)i hated the pump in the boat and the hoses in the splashwell.bought i new CMC hydrojack(5.5" setback)and put that on in the end of may.took some time to get it dailed in.now the problem!
I LOST ALMOST 5 MPH ON GPS!!yes,same prop,same rpm(must be more slip)Why???more setback should allow me to carry the bow even better.i've been messin' with it for a month or so,i'm stumped!!! any help???

us1
07-13-2001, 05:32 PM
Did you set the motor higher off the bottom than it was with the 1.75 inch set-back? The farther you move back the higher the motor need to go.

84exciter
07-13-2001, 05:38 PM
not at first,the old plate i could only go up 4.5 inches b4 i lost water pressure,at 1st i set this one lower then i moved it up.as it sits now i can't quite go all the way up b4 i lose water pressure(about 5"up on the jack then press. drops off.((not lwp on nosecone)).

us1
07-13-2001, 06:06 PM
Sounds like you might need lower water pickups to get the motor up where it likes to run. Picture your boat from the side when it’s going wide open. Typical attack angle for most hulls is 3 to 6 degrees. The further back you are moving the motor, with this angle your running at, the lower the motor drags in the water. Not to mention you’re new found bow rise adding to this angle.

84exciter
07-13-2001, 06:10 PM
john,
i wasn't looking for MORE speed.everything is the same as last year except the jack,i should get the same speed with less trim( or the same trim)just didn't want to slow down

us1
07-13-2001, 07:02 PM
We are not talking about trim or increasing speed. Merely returning the boat to its proper balance with your new set-back to get back what you lost. The angle of attack is the angle of the hull verses the water. This angle will increase with more setback. Plus the added distance of the new position of the motor away from the transom will require you to raise your motor to reduce drag. It very well could be something else, but this is the most obvious place to start looking. Good luck.

84exciter
07-13-2001, 07:15 PM
john,
i thought the added height you needed was because the water rose behind the boat,so in threory,the motor goes up,the water goes up,should be about the same place i was before.or am i missing the big pic?i can raise the motor till i start to lose bite on the prop,quite noticable,b4 i lose alot of h20 pressure

us1
07-13-2001, 07:35 PM
It hard for me to diagnose without seeing and driving the boat. Your comment about being able to blow out the prop means you are close to the right hight. I usually raise the motor until the prop blows out or get a little loose then I lower it ½ to 1 inch. Are you running a surface running prop? Do you have stock water inlets, because if you do and you can get the prop to blow out while still maintaining water pressure smoothing is wrong. The prop is still under water at this point.

84exciter
07-13-2001, 08:00 PM
john,
the the boat is an 19' checkmate exciter,2.6 gt johnson,omc 25" shooter over/thur hub,cmc jack,l&s cone w/o lwp.hyd steering.the prop starts to blow out as the water pressure is dropping off(15-17 psi,all is ok,10-12psi good prop bite,after that9-10 psi prop slips)hope that helps.
ps-i get a rooster about 2 foot high at half trim and half jack(14-15 psi)if i jack up the rooster gets higher,about 4-5 foot but speed doesn't go up.rooster never gets above 5-7 foot high unless i try to do so(4500 rpm 1/2 jack,full trim)it's not fast that way i know but alot of people think it is(idiots)lol
btw im truning 62-6300

[Edited by 84exciter on 07-13-2001 at 08:04 PM]

us1
07-13-2001, 08:30 PM
It sounds like the prop doesn't like the new setup. At 6300 RPM what speed are you getting on GPS. I'll run it on my computer

84exciter
07-13-2001, 08:43 PM
last year-69.9
this year-65.4

us1
07-13-2001, 09:09 PM
I forgot to ask you the gear ratio you have.At 1.86:1 it look like your close to 30% slip. Not to great. Even befor you had alot of slip. You mite have amplified a lingering prop problom with the new setback. I would try some other props with a larger blade area or four blads or even an over the hub Chopper.

84exciter
07-13-2001, 09:12 PM
the manual lists .538(14:26)
btw john- the shooter is a 4 blade
i've also run a 28 chopper 3 blade at no speed increase(last yr. 69.9???)?

[Edited by 84exciter on 07-13-2001 at 09:16 PM]

us1
07-13-2001, 09:19 PM
Sorry, put the wrong prop size in, it 18%.

84exciter
07-13-2001, 09:21 PM
thats a little better,but not great by a long shot

us1
07-13-2001, 09:37 PM
Ya know, I’m just looking this whole thing over and I’m wondering if you have lost RPM as well as speed or just speed.

84exciter
07-13-2001, 09:41 PM
just speed,the motor turned the same rpm last yr as this b4 the prop slips(if i jack it more the revs go up from there)

us1
07-13-2001, 10:01 PM
It really sounds like the prop is not happy in its new configuration. The whole problem is, you have lost prop efficiency form a small set back. I would try some other props and see what works. The prop wasn’t that efficient before you made the changes. With the right prop you should run even more efficiently than before the new setback.

84exciter
07-14-2001, 03:26 PM
i'll mess with a few props

Sleekster
07-18-2001, 01:33 PM
A ton of props to try there. My 235 loved the 26 Laser II.

84exciter
07-18-2001, 08:43 PM
hey sleekster,
not gonna make the rumble this year(i'm really bummed)but already planned a trip the very next week.when instigator told me about the rumble i was stoked,until i checked the calender.i hope to borrow a raker from a guy at the lake were going to in aug.thanks for the offer though!!!

Sleekster
07-18-2001, 09:34 PM
I'll be testing a bunch too. Sorry you can't come. I know my plan is to have a ball, and whoever shows, will just have to have fun too.

I like the Rakers and since you are running your prop wet, should be a good one. Try one that's a virgin. Reworks have ruined a bunch.

I had a spitting carb, #6, that was due to a reed cage gasket blown in. The other problems I had were from a bad brain which a transplant fixed. Hope you find the problem.

84exciter
07-23-2001, 03:34 PM
met up with sleekster yesterday,had a blast!he was nice enough to let me try his 28 raker.it ran 5900 at 64 mph,gps.
ok,i'm stumped!!i'm gonna through on the 28 chopper and give that a whirl this week,should get some good #'s out of that.any ideas anyone????

Sleekster
07-23-2001, 05:20 PM
Nice to hang out w/ you too. I forgot, what did you say to pour into the holes on the Raker?

84exciter
07-23-2001, 05:38 PM
or any 2 part,paste epoxy tape over the inside of the holes
you can even tape over the outside too

Sleekster
07-23-2001, 05:46 PM
After I get a new motor mount out of teh Hide n Seek garage.

Instigator
07-24-2001, 02:32 PM
I had the same thing happen after adding plates w/6" set back to my Sonic.
No other cahnges and I lost almost 5 MPH's!!
We spent about 2 hrs testing with jack plate height (manual plates) before giving up.
My theory is, that there is definately an optimum amount of set back for each paticular rig.
I am suprised that your boat lost speed by going back that amount due to the fact that your boat is bow heavy like mine and normaly would pick up speed??
Back to the optimum amount deal.
I already had a 20" set back bracket on my Sonic before adding the additional 6" from the plates.
The funny thing was, 20" set back is what the guys at Sonic and the bracket builders told me would be best for my boat!!
Have'nt had the time to switch back yet.
Another consideration on yours is that if you are running a four blade, they are typically smaller dia. than a three which might partially explain near 20% slip??
For grins if you have'nt tried it yet, try dropping the plate back down so your prop gets a good bite and see if your efficiency comes back up.
Also, your theory on why you raise the motor on additional set back is correct.
One more thing to look at. If you know your "before" shaft height, compare it to now.
Should be able to raise some to compensate for the angle (usually 15*) of the motor board mounting the plate at a lower level due to the angle. (assuming zero lift on the plate)
Hope this helps and good luck!
I know it sucks when changes go bass ackwards of they way you and everyone thinks!

84exciter
07-24-2001, 09:22 PM
i ran sleekster's 28 3 blade raker on sun,turned 5900@64mph.i'm stumped!!i'm gonna try my 28 chopper this week.keep your fingers crossed

84exciter
07-28-2001, 04:49 PM
i run my 28 chopper today,we only have about 1/2 a mile straight to run flat out.last year it ran 69.9 on gps,today it ran 72.9 and had more to go!!!!!!i guess the shooter didn't like the setup,but the chopper does.now i don't have to sell the new jackplate.
p.s.-i also got to pull a nice 'stream in 2day,had a 115 on it.(can you guess who made the motor????)hahahahaha.

Sleekster
07-28-2001, 11:19 PM
Just wondering. I finished instsalling the plate and swaping the top motor mount. The friend that meade it was way off on the measurements. Motor acted like a jack-hammer on the transom. I'll never do that again.

Congats on the speed increase.

84exciter
07-28-2001, 11:51 PM
hey,how are you?
the chopper is a merc,14.5x28

Sleekster
07-29-2001, 07:57 AM
What r's were you turning? Might be able to calculate your slip. us1 was on the money on this one, huh?

This board sure is a tremendous asset.

84exciter
07-29-2001, 11:03 AM
thanks guys, for all the help.

it ran 72.9(gps)@6100,i know the slip will be high but it's not an allie/'stream,she weighs 1278(dry) plus 396# motor,shis,gen.boating ****(ie;anchor,etc)170# me,32 gals fuel,oil,bat,etc. not bad for a FAT CHICK! lol

us1
07-29-2001, 11:19 AM
It’s always good to here good results.