jackplates and setback

[Ron G]

Iwant to have a discussion on setback,how it effects and hampers in different applications,the reason for this i was talking to guy with a boat like mine and he said that when he put a 10"plate on it he lost 5 mph but when he went back to the 8"it ran a whole lot better.i would think the father back you get the better water you get.i know everytime i learn one thing about props and set-up the dumber i feeldtheres just alot of varibles to track down.but it is fun

 

[Dhadley]

Re: jackplates and setback

Think of it as a balance issue. There will be a point on any given hull that more becomes too much. (Kenny will elaborate) When you move the motor you're changing the fulcrum point. Once you get to / at / near the right spot, a little makes a lot of difference.

When you move the motor (weight) back you're also moving the thrust source (prop) back. Again, depending on the hull configuration you'll find the "sweet spot" back there somewhere. The water won't be as aeriated and the prop will hook up better. A couple inches back and the balance gets outta whack and you'll either slow down or have handling issues.

 

[Dhadley]

Re: jackplates and setback

You also have to look at the load distribution in the boat and the weight of the motor. You have a pretty light motor, all things considered. If the other guy had something heavier, like an OMC 90* looper, then the 2" will be different on your boat compared to his.

I wouldn't change plates for the 2", I'd use the 2" spacers to test. Lots cheaper. And quicker. And easier.

 

[walleyehed]

Re: jackplates and setback

Ron, I kept going back farther and farther with mine, and I found what "too far" was.
I had been running with a 4" plate, and had good results but still felt I needed to find out how much more I could go, so I installed a 6" plate and gained a respectable amount with the props I had been testing with the 4", so I had to install a set of 2" spacers to see just how far I could go without buying a 10" plate.
As it turned out, with the props I was "testing", I started to begin a porpoise that I had to adjust my smart-tab pressure to max (80lbs) to control with neutral trim.
When I got done testing that series of props, I went back to my favorite Raker that I had worked for all it was worth.
When I blasted off it imediately began to porpoise with it trimmed clear in, so I went to WOT and darn near lost total control of the rig....on the third bounce, the boat completely left the water with the nose headed sky-ward, and a really hard landing followed. I banked it, looked at everything I could think of and decided to change props...I went to the Turbo1 and it wasn't "quite" as bad, but a steady, level ride was still out of the question. I banked it again, looking for something I might have missed-found nothing out of whack...at this point, I was really lost because the Turbo1's had been the best over-all performers and then I realized I hadn't tested those, or the 20P Raker with the total setback I had now.
I had a TXP with me and installed it...BINGO!
I had my answer...I had shifted the weight TOO FAR back and the TXP being an over-all lifter, provided a flat ride, and I could go past neutral slightly before porpoise started.
In this whole deal, I found where my balance point became a serious issue when I passed the sweet-spot.
I'm installing a Bob's 4-in-1 due to the 5-1/2 down to 2-1/2 size range.
I actually had 2 spacers with this set-up...a 3/4" before both plates, and then 2" spacers after trying the 6" plate, so I had 8-3/4" on this deep-V alum.
In this case, I think a total of somewhere between 5 and 6" is going to be the best in the end.
I also learned there is more than 1 way to wet the wallet....in my case, I was still in the boat........front AND back of my pants got wet....8)

 

[Ron G]

Re: jackplates and setback

ddive done about all i can were im at now,my plate has slots in it were i can push it in ,i may have to see if i can do that and start over again with the testing also i may adjust the negative trim and see what happens.i should know real quick.because its doing great right now but i need moredi got a tourny this weekend so im going to pre-fish saturday that should give me some good numbers.Thanks for the education.
Dale did you ever talk to the guy about my prop?

 

[Dhadley]

Re: jackplates and setback

Yep, he said they'd work it over whenever you'd like to send it. No problem.

 

[Ron G]

Re: jackplates and setback

Thanks Dale i'll be getting in touch with ya here soon.

 

[Dhadley]

Re: jackplates and setback

Cool.

 

[Ron G]

Re: jackplates and setback

I didnt lower or do anything to my set-up,the boat ran like a bat out of hell this weekend i was by myself but still.alot of stuff went wrong loike my water prassure gauge went out again the speedo started leaking water on my foot and the fish didnt bite but it was fun.blasted off and i was rolling.was abale to drive with out any chine walking just rolling dont know how fast didnt have a gps but the speedo said 58 and im pretty sure i was in the high 60 thats the fastest its every run.do think adding the pvs(?)plugs will help on the txp?
And one more thing at around 5000rpm the motor gets a rattle to it????sorta like plastic a rattling it doesnt affect anything and i could'nt see anything loose is possibly reeds?or do i have something else going on?

 

[Dhadley]

Re: jackplates and setback

The vent holes will allow more venting on holeshot but shouldn't change anythig on top end. Bigger holes = more venting, smaller = less.

Is the rattleing when you're cruising or as you slow down?

 

[Ron G]

Re: jackplates and setback

When im cruising,theres nothing at idel or up to around 4800 then it starts.its sorta hard to describe like plastc a fluuttering really fast.

 

[Dhadley]

Re: jackplates and setback

When it's doing that have you tried bumping the primer?

What spark plugs are you using? 87 octane, right?

 

[Ron G]

Re: jackplates and setback

No i havent bumped the primer.i but new plugs in last month,the ones you recomended the q78s i think.and yes the 87 octane.

 

[Dhadley]

Re: jackplates and setback

OK, the next time it does this hit the primer. If it's what I think it is the motor will instantly blubber worse and lose rpm. IE -- bumping the primer will flood it instantly.

There are a couple of things that could cause this. One is the motor being excessively rich at that particular rpm. With a carb'd motor there isn't a lot we can do about that without adversly affecting the motor at another rpm level.

Hitting the primer at any given rpm will tell us one of 3 things --

If you hit the primer and the rpm picks up for a second and then the motor blubbers and looses rpm, it's too lean.

If it doesn't do anything for a second then blubbers, it's just right.

If it instantly blubbers it's too rich.

I have a feeling that your motor might be slightly rich at that particular rpm. If so, it won't hurt anything but I agree that it's annoying.

There are a couple of other things to consider. A weak spark may cause the same issues (not enough spark for that amount of fuel). That's usually a slightly dirty ground on the coil pack or a weak wire. Cleaning the gounds on the coil pack and power pack never hurts. Also pull both the plug wire and the orange primary wires on the coils. Those terminals get dirty pretty easy.

 

[Ron G]

Re: jackplates and setback

so i can do this at idle?i'll have to get my manual out and clean the grounds,it dont sound to hard.i know its getting old and eventually is going to need to be freshened up,but i sure dont want it blowing on me!i guess i better ask a good prop question to keep this,so if i get the holes put in will that help with my hole shot with the extra person?i know we been over this but the boat is an entirly different when you throw that extra person in it regardless of the weight of an adult.....its got me so confused.

 

[Dhadley]

Re: jackplates and setback

Well, I wouldn't pull any wires at idle....Lol! But yeah, just look over the grounds and especially the primary leads on the coil pack.

Yes, hitting the primer at any rpm will tell us what's going on at that speed. But the next time you're at the rpm that it's making this noise just try that and let's see what happens.

As for the vent holes you can make them bigger and it should help the bottom end with the extra person. You could put the Merc PVS size holes and then get the inserts with different size holes. Any prop shop should be able to do that.

 

[walleyehed]

Re: jackplates and setback

DH, just curious about this...are you thinking maybe an intermediate range, lean condition being a possible cause of the sound?
I'm not up on Ron's engine style enough to recall from my mind, but I had a lite "ping" at cruise this spring when it was cool and I had to go up on my intermediate jets 1 size, which eliminated the ping, but I went back after it started warming up outside.
Thinking (asking) out-loud I guess.

 

[Dhadley]

Re: jackplates and setback

Some 60* motors in certain applications in certain situations make a funny "ratteling" noise. The most common scenario is on hard decelleration. Engineering called it "de-cell knock". Some will sound like a rod came loose when in fact nothing is wrong. It goes into a lean mode upon decelleration, like all carb'd motors, but these make a loud noise. OMC had made some enrichment systems that kicked in on decelleration and that stopped the noise.

We have heard it as Ron describes and many times when it's at a steady rpm it turns out to be a bit rich at that given rpm. Now, "rich" may mean too much fuel or too little spark advance or even a slightly weak spark. We're hoping in this case it's one of these "rich" situations. Those primary terminals can cause all kinds of odd problems if they get dirty or corroded, especially in salt water. I think Ron's in fresh water but we'll still see some build up and a high resistance. Just like a "dirty" ground connection. It works but just not correctly.

 

[Ron G]

Re: jackplates and setback

Thanks,and yes im in freshwater.Kenny its a 93 175 faststrike.i know it doesnt make the noise in the low rpm range just in the upper mid and espiacially the high range.i will do the primer pump may try to take out this weekend to try to get a jump on it.i will try to find all the grounds and clean them also.weres the primary terminals?and what do you clean those with elctrode cleaner?
Thats what i was thinking about getting the pvs holes with the different size inserts.

 

[Dhadley]

Re: jackplates and setback

I usually clean the hi & low terminals with a Scotch Brite pad and the Electra Clean spray or brake cleaner. The primary wires on the coil pack are the orange ones.

Once the terminals are clean it'll help to put a touch of dilectric grease on them. Don't use regular grease though........