Pro XS should have more ***Moxie***???

**FMP** · 10-12-2018, 06:39 PM

Diameter x pitch?

**home made tunnel** · 10-12-2018, 08:58 PM

Originally Posted by MARC1255BOATS

I just bought a brand new boat with a 20" Mercury 115 PRO XS with the std 2.09 gear case (not the command thrust). As soon as I got it past 40 mph it would porpoise so bad that it became scary. Yes you can trim it down to stop the boat from hopping but then you scrub rpm and speed. The motor is at the highest position so I can't go any higher. I know motors mounted too low is a major cause for porpoising but it's not the case for my application. I was running a 3 blade Mercury Laser II prop which produces a lot of bow lift (which I don't need). I'm now running a 4 blade Quicksilver Q4 (same prop as Mercury Spitfire Q7) which are stern lifting props. I didn't lose any top speed but cut the porposing by 50%. I did gain acceleration, lower planning speeds, and better holding power in turns. I can now run in a neutral trim position without bouncing all over the place. Personally this motor is a monster (in a good way) compared to my old Mercury 125. I've still got a lot more testing but that's part of the fun.

Dang - What kind of boat?? If you can't go any higher on the motor bolts, think about getting a jack plate. But A brand new boat should come setup properly (you'd think).

**flabum1017** · 10-12-2018, 09:19 PM

Originally Posted by home made tunnel

Dang - What kind of boat?? If you can't go any higher on the motor bolts, think about getting a jack plate. But A brand new boat should come setup properly (you'd think).

Buddy of mine bought a 27 Concept with twin 225 Opti's on it. Boat would only do 55 out of the box. After raising the engine bracket and the engines, we got her up yo 70. I'm sure we can get more out of her with nthe right props, but have not had the opportunity to borrow different props to try....

**home made tunnel** · 10-12-2018, 09:21 PM

Don’t we all just wish there was a big rack of props to try before you buy somewhere? Lol

**FMP** · 10-12-2018, 11:26 PM

Nope, not allowed

**home made tunnel** · 10-14-2018, 02:05 PM

New personal best. 60.8mph at 6100rpm. It was real choppy today.
No problem getting on plane. If I went slow to get on plane, it would blow out and I’d have to stop and start again.
The new motor height doesn’t porpoise at 50 anymore, but it now does at 20?! Lol oh well.
With the gps on my phone, I got to a solid 59mph, but saw 60.8 as a max, while hopping still, and trimmed up slightly past neutral. I still had 20psi water pressure at speed.
Dont mind the speed on the dash reading low... my paddlewheel/transducer was kicked up. I need to tighten the bolt to keep it down.

Im thinking a little more height may get more speed, and I might try the 26 pitch prop again.

May have to start thinking of a Bobs nose cone, strictly for a low water pickup on it.

Some numbers:
40mph at 4100rpm
45mph at 4600
60mph at 6100 (hopping/trimmed in choppy water). <- scary to me!

Improvents! I’m going to run it this way for Saturday’s Connecticut river run.

**FMP** · 10-14-2018, 02:14 PM

Clearance to case good? Maybe a bit higher and 26, need to spin the 6+ if that prop will bite and not get the bow high? Christmas wish list a good four or five blade

**FMP** · 10-14-2018, 03:39 PM

You're going to loose that camera or worse

**gotboostedvr6** · 10-14-2018, 04:05 PM

Go to a hull pickup before nose cone. You might need the propshaft to be level with the pad with that setup.

**Whaaaaat** · 10-14-2018, 04:16 PM

I'd like to see a video of what's going on around lower unit and transom at speed. With the motor that high and stock lower unit I wonder how you have any water pressure at all?

**home made tunnel** · 10-14-2018, 07:31 PM

Originally Posted by FMP

Clearance to case good? Maybe a bit higher and 26, need to spin the 6+ if that prop will bite and not get the bow high? Christmas wish list a good four or five blade

Yea clearance is good. I ground off another 1/16”. It’s got a gap of a couple credit cards now.

Originally Posted by gotboostedvr6

Go to a hull pickup before nose cone. You might need the propshaft to be level with the pad with that setup.

no way... that’s where I started and it ran like crap. I’ve gone a couple inches higher and it has been getting better and better. Why would you say hull mounted over low water pickup nose cone?

Originally Posted by Whaaaaat

I'd like to see a video of what's going on around lower unit and transom at speed. With the motor that high and stock lower unit I wonder how you have any water pressure at all?

me too!!! I need to find a friend with a go pro to mount back there. I think it’s splashing off the sponsons keeping the lower wet. ? Maybe. Idk. But it’s reading pressure regardless lol. Setup continues.

Thoughts on my next try? Up another inch and run the 26” prop?

**gotboostedvr6** · 10-14-2018, 07:41 PM

You bought the propshaft a few inches above the pad?

Are you using the stock water intake?

I'm confused a bit...

**home made tunnel** · 10-14-2018, 10:14 PM

Originally Posted by gotboostedvr6

You bought the propshaft a few inches above the pad?

Are you using the stock water intake?

I'm confused a bit...

see the picture in post number 66

**FMP** · 10-14-2018, 10:55 PM

Looks like any minute now and you're going to need a lwp or convert it to a Lycoming airboat motor. How much setback?

**home made tunnel** · 10-15-2018, 12:56 AM

Originally Posted by FMP

Looks like any minute now and you're going to need a lwp or convert it to a Lycoming airboat motor. How much setback?

Lol airboat motor.
I have the bobs machine standard manual jack plate... but I just realized I have it set on the 5” setback. I think I’m going to flip it around to the 2.5” setback orientation.

my jack plate: https://bobsmachine.com/product/conv...te-200-hp-max/