What Prop??

[jhow0228]

Got an 18' Bass Hawk with a Merc XR6 150hp. It's got a Quicksilver 25p SS Prop on it now. Runs great with it, but wanting to see if I could possibly find a better match. As it sets, boat absolutely jumps out of the hole and I really don't want to lose any of the hole shot, but was told that the prop could be what causes it to chine walk pretty bad. They say that the Quicksilver doesn't have enough diameter to hold the boat on the pad.

 

[Texasmark]

Re: What Prop??

Got an 18' Bass Hawk with a Merc XR6 150hp. It's got a Quicksilver 25p SS Prop on it now. Runs great with it, but wanting to see if I could possibly find a better match. As it sets, boat absolutely jumps out of the hole and I really don't want to lose any of the hole shot, but was told that the prop could be what causes it to chine walk pretty bad. They say that the Quicksilver doesn't have enough diameter to hold the boat on the pad.

You can shop brands of 26P props for that gear case and see what the diameters are. Most of them are within a half inch or so. I know that different props can give you different results with operation, but don't know the cause of chine walking. Usually the lower the pitch the larger the diameter; just the way the designs work out. If you lowered your pitch and got more diameter you would improve your hole shot but hurt your top end. Is the current prop ported? Have you discussed this with a knowledgeable prop shop?

Mark

 

[jhow0228]

Re: What Prop??

Thanks for the reply. No, I haven't spoken with a prop shop yet. May do that next chance I get. I'm not too worried about losing a couple mph off the top end right now. Just looking to smooth out the ride at WOT.

 

[Tail_Gunner]

Re: What Prop??

Got an 18' Bass Hawk with a Merc XR6 150hp. It's got a Quicksilver 25p SS Prop on it now. Runs great with it, but wanting to see if I could possibly find a better match. As it sets, boat absolutely jumps out of the hole and I really don't want to lose any of the hole shot, but was told that the prop could be what causes it to chine walk pretty bad. They say that the Quicksilver doesn't have enough diameter to hold the boat on the pad.

Ok lets get this started at least. Could you take a pic of your O/B leg straight down vertical with your transom. Lets see where your cav plate is in relation to the bottom of the keel another good pic is to see where the tip of the blade is..aka above the keel or below. Two things will influence chine walk...balance of the engine and tourqe of the prop...Look for Dhadley very experienced in these matter's.

 

[jhow0228]

Re: What Prop??



Here they are! Hope these are ok. If not, I will take some new ones next chance I get.

 

[Tail_Gunner]

Re: What Prop??

More like this..it shows the cav plate and where it rides in relation to the keel. It looks like your cav plate is well above the keel so one that show's the prop tip at its highest point aka is the prop tip 3" above the keel...Your setup may well lift the hull right off the water at high speed. Remeber your hull acts's like a wing at high speed.. now a setup that lift's the hull very high in the water and can combine that with a wing effect...You may just be flying..literally..

 

[Texasmark]

Re: What Prop??

More like this..it shows the cav plate and where it rides in relation to the keel. It looks like your cav plate is well above the keel so one that show's the prop tip at its highest point aka is the prop tip 3" above the keel...Your setup may well lift the hull right off the water at high speed. Remeber your hull acts's like a wing at high speed.. now a setup that lift's the hull very high in the water and can combine that with a wing effect...You may just be flying..literally..

This answers my "is it ported" question. I see one of the 4 holes. These help your hole shot and can be varied in diameter to obtain the desired result. The larger the hole the less stress on the engine and more rpms coming out of the hole translating into a quicker hole shot. Remember that rpms are one of 3 elements in calculating horsepower and HP is what turns the prop. So the faster you can get your rpms up, the more available HP you have to get out of the hole and the faster it is....also the faster you can pull up water toys....including water skis.

Ideally you want the perfect combination of increased rpms and decreased hole shot time. You can always drill out the holes (SS is really tough to drill) but if you over do it, it's another story to plug them back up; course the Mercury Laser II comes with rubber plugs so you can set whatever hole size you need easily....but that is a bow lifting bass boat prop and I see you have an I/O. If you decide to drill them out, make the diameter chane a little at a time. A change of 1/8" in diameter, say 1/4" to 3/8" can make a big difference. Just guessing, looks like yours are 1/4".

Nice thing about (port) holes is that once you are up and running, they close off and you pretty much don't know they are there so you don't have to sacrifice top end for a great hole shot. Exceptions would be in tight high speed turns and maybe slight over revving in certain rough water conditions. Course the solution to that would be to tuck your trim in till it stops.

Mark

 

[jhow0228]

Re: What Prop??

I'm actually leaning towards getting a 22p prop now. My motor is not achieving its WOT rpm range and I believe that is due to the high pitch. I will lose out on top end, but it will be minimal because I will achieve higher rpms.

 

[jestor68]

Re: What Prop??

What kind of Quicksilver prop are you using? It should be the Lightspeed(same as a Mercury Laser).

The demension you should be concerned about is the pad to prop shaft center line measurement(3.5 inches below the pad to start).

You never mentioned what rpm you're turning at WOT. The recommended range is 5000-5600.

You want it propped to run right at 5600. Some guys say to run to 5800 for max performance.

The XR-6 uses the smaller intermediate gear case, so the prop diameters are relatively small(like 3.5").

 

[jhow0228]

Re: What Prop??

Laser II is what I'm running right now. It is a 26p prop and I'm currently only able to turn about 4500.

 

[Texasmark]

Re: What Prop??

If I see what I think I see your engine is too high on the transom for no setback in pic #2. Pic 1 really is too dark and means nothing with that one can see in #2. But that makes no sense as too high with no setback would set you up for some really big ventilating problems and you are in the other direction not even coming up to minimum rpms at WOT.

Best thing for you to do is go to a prop shop where you can borrow a prop to test it. That way you can get the right answer rather than just guessing and be happy with your purchase even though you may pay a sizeable premium. It'll be worth the bucks. I would stay with a ported prop for your hole shot.

Personally running the boat would help loads but that won't happen so we just have to play the guessing game. I'm still curious about your 60 mph number and the results of the BAM prop slip calculator I showed you.

HTH,
Mark

 

[jhow0228]

Re: What Prop??

Unless my slip is truly minimal I'm not sure. I'm running at 59mph on my GPS at 4500rpm. I'm going out in the am and gonna really run it hard and see just what she is really capable of and will post back then and give you all the details. Oh, you're more than welcome to come on up and run the boat. Lol

 

[jhow0228]

Re: What Prop??

But I did reenter the numbers for a 22p and my gain in rpm will easily offset the higher pitch prop on overall speed.

 

[jhow0228]

Re: What Prop??

Just got back from the lake, at 4300rpm I'm running at 56mph. Had an extra person plus gear in the boat. I tried to push it on up higher but it would start walking uncontrollably. So I'm assuming I'm getting to WOT at that point.

 

[jhow0228]

Re: What Prop??

Talked to a prop shop just now. He seems to think my tach is off, bc the boat planes out very quickly and that takes over 5000rpm at the pitch I'm running but the tach never registers over 4500.

 

[Texasmark]

Re: What Prop??

Planing that boat with a 150 very quickly (3-4 seconds for me) with a 26P Laser with the larger dia port plug sounds reasonable. Since you gps measured your speed, then you can take that number back to the calculator and work backwards. 15% slip was just a guess. With that prop on a pad you may be closer to 10, maybe less.

On a bad tach not going over 4500 could indicated a sticking needle. You can buy another or get one of those cheap tachs like you have on your lawn mower. I think they are "Tiny Tachs". Be careful running it. Having a buddy along to monitor the tach while you drive would be safer.

Why don't you buzz a guy on here who goes by "Chinewalker". Since that's his handle, maybe he knows the in's and outs of the subject. Or ping the archives with the subject.

I ran a Ranger on initial outing after purchase and below 55 it was ok. At that speed it started doing it. The prop was too much for the rig and in reducing the pitch I gained other things I needed plus I couldn't get over 50 which solved the chinewalking problem I had. But it was my first padded boat and I was just a guppie; learning what's all about.

Mark

 

[jhow0228]

Re: What Prop??

On the tach I'm probably going to go with a cheap digital one that wraps around a spark plug to check it vs my original one which I believe is probably 30yrs old like the boat itself. One more question here. When trimming out, the rooster trail should only get as high as top of motor, correct? That's how high mine goes and I've heard before that that's the right height for it.

 

[jhow0228]

Re: What Prop??

15% slip was just a guess. With that prop on a pad you may be closer to 10, maybe less.

The prop guy I spoke with told me to expect about 20% slippage, so using the BAM calculator you showed me, I am pretty spot on with running 60 at WOT(5500rpm).

 

[jhow0228]

Re: What Prop??

Let's say for arguments sake that my tach is spot on, what do you think about going down to a 21p 4 blade prop?