Just plain weird! UPDATE!!!

[LubeDude]

I run two different props, a High five when Im loaded with more than two people, and a four blade Turbo when Im by myself or one other. The four blade is slower out of the hole, but runs smooth through all RPM Ranges, 5,400 WOT However, the High five which I love, 5,700 WOT is so erratic that I almost hate to use it. It has a torque thrust type hub and it is fine so I have rulled out any slipping. Feels like an electrical problem but it only does it with the high five prop, (Does what)?<br /><br />Say at 3,500 RPM, it will go from 3,500 to 3,700 then back to 3,500 and back to 3,700 continually. Also, when I take off and get on plane after about 10 seconds it seems to shift like a powerglide, Im not kidding, it sounds just like a 2 speed. Once the Rs go down, (shifting), it doesnt go back up other than the slight change in RPM. Whats up with this?

 

[Dhadley]

Re: Just plain weird! UPDATE!!!

Whats so unusual? Thats exactly what some props do when they are at the max X dimension. With performance boats we actually try to get them to do that. At low rpm it slips and revs up therefore getting the r's up quicker. As the boat noses over the prop hooks up and youre on your way. Acts just like a 2 speed. <br /><br />As for the difference between the 2 props you arent comparing apples to apples. The set up is maxed out for the hi-5. The Turbo might need a bit more X dimension. At 5400 max the hole shot will be less than the hi-5 at 5700. Assuming both are close in pitch. obviously the Turbo hooks up better at the same height.<br /><br />I bet it took a lot of work to get it that good. Congrats!

 

[LubeDude]

Re: Just plain weird! UPDATE!!!

I understand the hooking up as you describe, but it takes a bit after it breaks over for it to hook up, maybe 50 yards or so. The High five has very large ventilation holes, maybe made for plugs and they are all removed. The holes are big enough to stick your index finger in. Could this have something to do with it?<br /><br />Is the slight change in RPMs indicative of this? <br /><br />This is all taking place without any trimming at all.

 

[Dhadley]

Re: Just plain weird! UPDATE!!!

That could indeed have some bearing. See if you can get the plugs and try slightly smaller holes. youre real close to as good as it gets with a given prop. You must have a ton of time in this.

 

[sangerwaker]

Re: Just plain weird! UPDATE!!!

LD if the vent holes are that large, the plugs are definitely removed. I run the same prop in different pitches, so I'm very familiar with it. The plugs are available at your Merc dealer and are about $.50 each. Get five and plug all the holes but 1. Save that for a spare as they damage easily. The holeshot will be slower, but it may fix your RPM issue. Maybe not, but I think for a couple bucks it may be worth a try.<br /><br />You can experiment with the holeshot by removing another plug or two.

 

[walleyehed]

Re: Just plain weird! UPDATE!!!

LD, the MWC Edge II I have does very simular things at mid-range...the RPM hunting.<br />It also slips alot before the bow drops and does just like you say...it appears to shift. My Raker really does it if I take off without it most all of the way down, but pour the coals to it and it hooks up and scoots-gone-flash........<br />I have 2 props that are very touchy in the mid-range area and won't hold a throttle setting to save your butt...BUT, I have found the props I run that vent for what appears to be longer than they should and do the "shift" thing, are my best running props over-all.

 

[sangerwaker]

Re: Just plain weird! UPDATE!!!

LD, I took a couple of pics of my High Five vent hole. I have one of the PVS plugs removed on my 21 pitch. The first pic is the opening itself. The second is with a penny in the hole for size reference. The third is with a PVS plug in.<br /><br />All of these are LARGE files. Raw digi files.<br /><br />Pic 1<br /><br /> Pic 2 <br /><br /> Pic 3

 

[LubeDude]

Re: Just plain weird! UPDATE!!!

So I want my boat to sound like its shifting in and out of overdrive all the way accross the lake?? I feel funny telling my clients, "Oh ya, its suppose to do that because I have the optimum set-up"????

 

[walleyehed]

Re: Just plain weird! UPDATE!!!

Mine does the same thing, LD....I just up the R's or trim in just a tad and it stops.<br />When on plane, I don't "think" the PVS holes are causing you any problems..Lower the engine a half inch if ya need to....compromise a tad.

 

[dtherrien]

Re: Just plain weird! UPDATE!!!

LD,<br />I have a 4 blade trophy plus on a merc 150efi.It also has vent holes in the side.They are about 3/4" in dia. I started to have problems when all but one of the plugs fell out....i was getting alot of prop slip.So i went to the auto parts and got some plugs (body panel type) and plugged them all up.Now it runs fine...hooks up great...but has a little shutter to the motor at idle. I think that some exhaust is suppose to be released through these holes.I checked at the marina and you can get plugs with differant sise holes in them....you just have to experiment.<br />So when i first bought the boat it would come out of the hole and then hook up (like you said...50 yds)sounded like it shifting.But thats the only time it would do that....it wouldnt do it off and on like yours.

 

[LubeDude]

Re: Just plain weird! UPDATE!!!

Originally posted by walleyehed:<br />[QBLower the engine a half inch if ya need to....compromise a tad. [/QB]

Na, cant do that, its perfect for the four blade Turbo, its a 15" and the High Five is smaller by a bit, Thats where the problem lies. I can live with it now that I know its ok. Sure have a lot of people wonder whats going on though.

 

[LubeDude]

Re: Just plain weird! UPDATE!!!

Boy, do I feel dumb!!! <br /><br />I picked up my High-Five and was messing with it and noticed that the peice that the nut tightens up too was a bit lose. Upon closer inspection and actually removing the hub, (Flo-Torque), its cracked in about four places. SOOOOOOOOOOOOOOOOOOOO, What I thought was a good hub is actually garbage and that is where my eratic performance was coming from.

 

[walleyehed]

Re: Just plain weird! UPDATE!!!

Good find!!!<br />Have you ran the Scorp yet???

 

[LubeDude]

Re: Just plain weird! UPDATE!!!

Originally posted by walleyehed:<br /> Good find!!!<br />Have you ran the Scorp yet???

No, I went out and tried to fish Saturday, but got blown off the lake. No more fluctuation in the High Five though.<br /><br />I hope to try it soon.