Originally Posted by RunninRed

....If you know the details of which box and shorty to use, what the drive height needs to be....

Originally Posted by socalstone

A shorty by itself doesn't do much if anything, but when combined with the extension box, it makes a big difference. .

Originally Posted by Wild Card 09

I ran my newest mod the other day. Adding to the 3" lift of the extension box, I fitted a Imco 2" shorty lower. This brought the propeller shaft up to only 2 1/2" under the pad. I was hoping that by reducing the amount of drive in the water, I might find yet another mile.



But no! not a chance.



I tried three labbed Bravos - 28", 29" and 30" - and a labbed 26" Maximus.



On the first run with my old favorite 28" prop, I was encouraged by the fact that the boat came up only slightly slower on plane, with no slip or cavitation. The 525 actually doesnīt have much torque low down, so the additioinal grip that the noseconed shorty shape brings keeps everything hooked up, anyway.

Mid range was a little slower already, and I felt that the boat wouldnīt trim up and air out.

I was all over the revlimiter at 3/4 throttle, with 71 mph on the GPS.

I turned back to the dock thinking that the higer pitch was going to do it.



The 29" was no great help, and the 30" was even worse. The motor could hardly creep up from 1500 rpm, until we levelled off. Less revlimiter but no more speed.



The Maximus was better, and brought us up to 74 mph at just under the 5350 rpm. Still could trim the bow up. Essential for speed on a non-stepped Baja hull. The boat felt dull and boring to drive.



Time to go home. You canīt win them all, right?

I had a 1" spacer with me but the the day was turning cold.



When we get another warm weekend day, Iīll be back on the water with 3 1/2" prop to pad, and refreshed optimism.

Originally Posted by Wild Card 09

First of all Iīm going to cover all the bases with drive heights and props.



Itīs alot of fun feeling how this hull changes itīs character with every settup that I run.



It was so much more capable with the standard length XR on the box. Powerful trim response and really capable cornering. At the moment the trim hardly has any effect at all, and the prop cavitates in tight curves at speed.



Iīm not looking for a pure straight line speed machine, anyway, but I want to know what can be achieved.

Originally Posted by Wild Card 09

As Iīve gone this far, Iīll probably end up trying a 1 1/2" or 2" spacer on the Imco lower as well.



My original plan (on fitting the 2" shorty) was that the noseconed lower would give the prop some of the bite that the high x was losing out on.



However, I didnīt realise how essential the low(er) x was to lifting the bow. Going down with the x in increments, until I get the bow lift, and therefore the speed, is the sure way to find the sweet spot of this settup. At the moment it is the lack of the sharp handling that I miss as much as the speed.



At the end of it all, I would like to keep the Imco. It sure does look sexy...but if the girl canīt cook......

Originally Posted by Wild Card 09

Ran the boat on Sunday with a 1" spacer on my Imco 2" shorty. I hoped to get the speed of the standard length XR back.



No chance! The reaction to trim has returned.



I can lift the bow more, and the boat feels a little lighter on itīs feet than before, but it still doesnīt sing the way it does with the stock lower.

The slip is down, so that Iīm only mildly into the revlimiter at WOT using the labbed 28" Bravo that takes the boat to 80 mph in combination with the XR lower.



But I was messing around in the low 70īs.........



It would seem like the hp/weight ratio that my boat runs does not justify either a higher x (than my 3" lift box brings), an Imco lower or a Maximus prop.



I still have a few more moves to go.......



Learning by doing...........

Originally Posted by Wild Card 09

I ran the boat last weekend with a standard XR drive, to get my speed back.



Nothing improved.



With a 2" shorty, 1" shorty and a standard XR all within 2 mph of each other, and well below my 80 mph speeds of last year, I should have figured that something else was up.........

My 525 hasnīt missed a beat, and runs all the right pressures and temperatures. Only the port header seemed to be a tad hotter than it used to be.



Would you believe it was the goddamned exhaust tips!



I had been running my CMI clamp on mufflers for the last three runs, so didnīt hear that the flappers....had both gone AWOL. Well nearly - the starboard one was gone, and the port side was wedged in..only giving me about a third of the opening.

Iīve read the threads about these things breaking, but didnīt think that on my freshwater trailerboat, this would be an issue.



Eddiemarine tips, fitted in july 2005. You never stop learning.........



So now the Imco is going back on!



And to really raise the game, it will be a brand new 2008 600SCi that will be

powering it.



The 525 was still warm when it was lifted out, yesterday.

The 600 was fired up this afternoon.



Mercury Racing are bringing some props to try. At the weekend we will put a couple of hours on the rig and get the feel of it.

Originally Posted by Wild Card 09

Yeah, I wish that I could have run a fair showndown between the lowers at the 80 mark. Now I know that it was simply the port tip that was reducing the power output, I can factor that out.

All three settups were within a mile or so of each other, with the standard XR being the fastest...at 73 mph. Now figuring that the noseconed Imco only starts to work at higher speeds than 80, and that is where I was with the XR, and the full 525 propshaft hp, I give the Imco a pretty good chance of being my final choice. Probably the one inch spacer was right, too. I had all the trim and bow lift I needed, with it fitted.



The extra power, and particularly the torque of the 600 is going give me even more bow lift. So maybe I can lose the spacer, to get more metal out of the water, and gain more speed.



First of all I shall run the baseline standard XR, because I know how the boat ran with it last year.



Tomorrow the Mercury Racing engine specialist is coming down from Belgium to do the final check on the installation. Heīs bringing some props to try, and we will get out on the water, checking everything on the laptop as we go. I get the impression that they are taking this seriously, and I sure do appreciate that. Yet another reason to pay the premium for a blue motor.



My prediction is that I will be wowed by the acceleration, and that I should see a good solid 85 mph using a labbed 32" Bravo 4 blade.

Originally Posted by Wild Card 09

Here you go!.

As I said, my last run with the 525 was on Monday. On friday afternoon we test ran the 600. It is amazing! Very different character to the snappy little 525. It runs really smooth, and particularly surprised me by being really gentle on the drive when idling. The electronics seem to control the shifting so perfectly. Now, when I brought the boat up on plane first time, the snarl of the blower and the torque really took me by surprise, and put a big grin on my face!

The labbed 30" Bravo was way too short, and we swapped to a 32" after a few minutes. I have a 32" and a couple of Maximusīs to try, but for the next few hours I shall just concentrate on breaking it in nicely (well, relatively...).

Iīm very happy having this monster of a motor in my 25OL. It fits easily, and although the motor is mounted 3" higher than stock there is still another 3-4" of space on top.

Originally Posted by Wild Card 09

So, to bring this thread back on track, the bottom line is that the Imco lower went back on an hour later, and ran really good. Mid range speeds were similar to the XR, and it trimmed out nicely. Water pressure was a little on the low side, but within the parameters set by Mercury. At 4500 rpm, I was seeing 1.9 bar, against 2.3 with the XR.

Iīm looking forward to getting some more hours on the motor. It is areal pleasure to drive. As expected of a well sorted product like this, there are no flat spots or vibrations as you accelerate, but the power does come on hard and fast, just as I had hoped!



Today I spent about four hours polishing the boat. You know the feeling!!!

Originally Posted by Wild Card 09

The motor has has now got 10 hours logged on it, and ran like a ....well just like the 525 did, with a whole lot more power and even more character..



I decided to go down a click, and run a new labbed 31" Bravo, to be a easier on the motor, and started the weekend watching the gauges continuously. Got to know the pattern. Cold start oil pressure is a remarkable 70 psi, dropping to 50 psi at idle when warm, and 65 psi at speed. After a run, the oil temp and water temp climb a couple of degrees. Otherwise everything looks the same as with the little guy. Fuel pressure always at a steady 62 psi (instead of the 525īs 40 psi)however hard the motor pulled.



On Friday afternoon, a run back to the marina next to Alexīs Pantera saw us slotting into the old routine and as many as six freight ships with a 1/4 mile of each other had both boats sharing generous amounts airtime as we battled for the honours!



I was watching the water pressure and the temp gauge for any signs of cooling issues. I had been warned that the blower motors (and particularly their Smartcraft Guardian system) are more sensitive to both fuel and water pressures, as this is how blower motors often meet their end. The motor seemed to really enjoy the action.



On Saturday, we did a fast run along the Rhein to a small lake where there is an enclosed race circuit, also shared by the local waterskiers. I took a couple of friends out and did ten laps, pretty much as fast as I could drive the boat. At the end of the straights, I had 77 mph on the GPS (where I was seeing about 71 mph last year). Trimming down to brake into the corner, and pulling tight around the bouy, planting the throttle and trimming out as we turn out (donīt try this with a stepped hull!!!). The acceleration had us screaming like wild men!



The 1" spaced shorty had just as much grip as the standard drive, and would not blow out even when turning tight!

(Note - I shall have to try running without the spacer, again).



With more hours and seat time I was running harder in the chop out on the Rhein. My passenger started to call off the GPS number as a stretch of consistent chop aired the boat out nice, and before I had to back off the throttle as the next freight ship wake approached, we had a new bestmark..........



84.8 mph @5200rpm