Kansas city area                     contact: rwosel@c-rmfg.com

                                                                            

Motec fuel and ignition

adjustment knobs while riding

Scoop grate/ride plate safety mod to eliminate inserts and grate pull out.

                     2009     Here's the graph on how the engine ran at Lake of the Ozarks after break in.


 From Idle I went to WOT ( Must have thought it was  slightly lean as I see I had to pump the throttle once)  And I let up when the stock speedometer  hit 60.  The data log is very accurate with time , so I started at 13.4 seconds  and ended at 16.8 seconds. That's idle to 60 in 3.4 seconds with the throttle pump.   This is the best that my XPL has ever ran.  .

   Top speed on the stock speedo put the needle at the bottom of the gauge at the letter D in the Bombardier logo. Estimate low 70"s. That's really neat to see the needle down there.

  

 Note the very lean Lambda readings, the readings read properly  up to WOT ( from 1.0 at idle to .83 to .85 just before WOT )  and then it   goes lean. I believe this is from the new air fuel mixture going through the engine and mixing with the exhaust air at the O2 sensor and showing lean as the air contains  extra oxygen . The EGT's read about 1030 to 1050 at WOT . These twin pipes have always shown lean at WOT. Perhaps my sensor placement is in the wrong place, and /or the pipes are very efficient. 



Click to enlarge.

Here is the test tank run that I did before taking it to the lake

The 1170 engine when first purchased was set up for 46 mm Novi carbs, a  Coffman pipe and a factory ECU module and  made 196 HP at the pump on my dyno. This equates to about 205 at the crank, once you factor in the loss through the driveline and all the bearings and seals  in the absorber and driveline.

  The 2012 upgrades included a Motec EFI conversion, Factory twin pipes , 46 mm Throttle bodies and the C125 dash.

 HP was now at 240 with speeds at 73 mph in racing trim.

The 2025 upgrades are 56 mm throttle bodies, more compression  and better tuning. We expect 7800 rpm and 75  mph.

​

                                                             History of the 99XPL and my association with Mel Miller


I purchased the 99XPL new, enjoyed it for the rest of that year and then the fun began. A 25 HP nitrous, then a Rossier big bore engine package  was installed and used for the next few years , along with the nitrous system. I don't recall ever being beaten in any races. The dyno proven Rossier engine is for sale , see for sale tab.

  Then I purchased the 947R, drove it that year and contacted Mel Miller in 2008,  as he had the reputation of building the 947R and was the go-to guy for the best performance on these engines. Mel designed cylinder sleeves  for this particular engine as well as purchasing an 1194 billet alloy steel crank assembly and performed the complete build.  I ran the engine the following year with a Coffman pipe, 46 mm Novi carbs and the stock ECU. Next I purchased a set of "short" twin Factory pipes along with his special Q domes .  I then converted the engine to Motec EFI. Mel immediately saw the advantage of EFI and he converted his race boat to EFI. I furnished several fuel system items including tooling to enlarge the DI throttle body bores. I continue to machine performance parts for him and we talk daily/ weekly on 2 stroke performance.

2" thick notebook of the complete build & spects.

including wiring, water flow & invoices of parts

red button clears alarms , green button switches screens  


​                      240 HP Big Bore Stroker 947R Miller built engine

Performance built by the 2 stroke Master Engine Builder , Mel Miller. This engine is a BRP 947R triple port factory racing engine making 240 HP at 7500 rpms. ( see a comparable dyno sheet below).   1170 cc's are derived​ from an 8 mm longer stroke and 93.45 Miller racing pistons . Honda CR500  connecting rods are connected to a  BRP racing 1194 super strong billet alloy steel heat treated crank with an oversize center journal and welded for durability, all by Crank Works of Tempe , Az. Crankcase includes a Miller billet aluminum cooler as well as a 947 DI water cooled magneto cover including the DI flywheel and ignition pick up for the Motec EFI system. 

   The cylinder head is by Miller and holds his custom 51 cc Q style domes that provide increased power. These have never been available to the public. Exhaust system is a Factory " short " twin pipe set up with  water solenoids for those extra few ponies.

   The pump is an extended Stainless 148mm Skat Trak 12 vane unit with a 14/19  impeller and an 87 mm nozzle. Peak rpms are 7550 at 73 +/- mph. Acceleration / speed is quicker that most of the stock ( ? ) 260 HP SeaDoos.

   The best feature of this craft is the conversion to Motec EFI including the massive spark of an MSD Dis 2 ignition box housed in a Pellican waterproof case and using MSD High Output ignition coils.

   Those of you that have a performance engine using 46 or 48 mm carbs know how rough running and rich they can be  at cruising speed and the excessive amount of fuel they use.  With the Motec unit controlling 56 mm  throttle bodies, acceleration is supurb and  cruising is as smooth as silk and very fuel efficient.  With the Motec you have full control of fuel flow at any rpm and any engine load, and the same with timing.

   The Motec EFI box is a Model M600 which will control up to 6 cylinders and 2 oxygen sensors, one for each cylinder plus data logging. The EFI electric fuel pump,filter, and the fuel pressure regulator are from Kinsler Racing in Michigan. System pressure is 45 psi. AN hose and fittings are used for durability and safety.

   Throttle bodies were designed and built by Miller , they're 56 mm  and can be enlarged to 60 mm and contain 130 lb. matched injectors from Injector Dynamics .

   All the stock gauges including the trim unit have been wired to work with the Motec EFI box. A Racepak recording RPM/EGT gauge has been installed into the LH mirror pod. Any SeaDoo DESS key will start the craft. The XPL retains all it's stock looking appearances and is considered a " sleeper".  In 2015 I traded all the above gauges for a Motec C125 dash which has a  data logging feature for all the engine parameters.

    The cylinders are currently ( Dec 2010 ) at Mel Millers for overbore to 93.45  and RAVE valve work. Mel Miller and I both have new replacement pistons in stock .  I also  have 2 new triple port sleeves that will accept a 92mm piston for at least 3 more overbores.

   The crankshaft and balance shaft is currently ( Dec 2010 ) at Crankworks for a complete rebuild including new OEM bearings, seals, and CR 500  rods. We have    new billet replacement  cranks in stock , if ever needed.  All internal engine parts are available for maintenance/ rebuilds, no obsolescence here.

   The engine will be assembled in March 2011. Many pictures will be taken during assembly and will be posted at the bottom of this page as the build progresses. This engine was again rebuilt in 2024 and uses the same bore and crankshaft  as the sleeves Miller designed just don't wear down.

So, you may be thinking, I wouldn't know how to adjust the fuel and or timing or even know when or if I needed to????

   No worry, as the tuning is easy and you'll never get fuel on your hands, no need to even open the hood and you can review what changes to make and even make them while sitting on your couch enjoying a cool one. How ?  Well that's the data logging feature that I'll explain. The only items that you may need to adjust is fuel and timing at WOT to match the fuel you are using, which should be 110 octane or higher, I ran C16. I can show you how to read the data log and make changes in an hour or 2. Everything else on the Motec has already been programmed and has been running for 13 years.

   All Motec computer programs are free to download plus there are various webinars on set-ups , tuning and program operation. The most difficult area of the Motec EFI is setting up a new engine. This has already been done for you. In fact, if you want to set-up another similar engine, you can use my program , rename it , and wire up the new engine the same way and tune from there.


​​ If you would like to read about the history of the 99XPL and my association with Mel Miller, there's an article at the bottom of this page. 

​   

2008  here are the build pictures from start to finish posted weekly as the build progresses.

​Click to enlarge and see notes

Expanded view of the power numbers

Important data for on water tuning

How To Tune the  Motec XPL 1170

You should  only need make small adjustments, if any, to get the engine running really well, and those would probably be at the wide open throttle area, mainly because of the overbore needing a little more fuel and to adjust the timing to your fuel if it's not C16. The engine will be safe and will run fine for break in purposes.


   The 99 XPL has 2 each 11 position rotary switches on the dash connected to the Motec EFI box. One is for fuel and one for timing. Position 6 is 0 on both with no changes to the Motec engine program. On both knobs, positions 5 to 1 decreases and positions 7 to 11 increase. See the chart below for a visual explanation:

position                    1        2        3        4        5        6        7        8        9        10        11

Fuel %                    -5       -4       -3       -2      -1        0       +1      +2      +3      +4      +5

Timing/ degrees     -5       -4       -3       -2       -1        0       +1      +2      +3      +4      +5


          There is a chart on the craft to remind you which way to adjust.

The fuel or timing can be adjusted while riding , just remember to always go + on the fuel first and - on the timing first and you'll not have any engine damage issues.

   So, with both knobs at 0 , lets go for a ride. Warm the engine for a few minutes and go to an idle for 5 seconds To get a feel of what the knobs do,  you could watch the EGT gauge, set to display the  maximun cylinder temperature,  and increase fuel 3 or 4 % and the EGT temps should drop and the engine may loose RPM.  And then go leaner by 3 or 4% and the idle should increase and temps will increase.  

   I generally start at idle and keep it there for 5 seconds, then go to 2000 , then 2500, ect. and use the fuel knob only to make it smooth. To start with, only concentrate on one rpm area at a time,make the adjustments and run it for 5 seconds , and head to the shore and jump ahead to the data log paragraph. After you've done it a few times , you can do several sites at one outing.   Once the lower rpms are adjusted , we can tune at WOT.    For WOT checks and here's where you need to watch close and act fast  as damage can come quickly.  For you , I would suggest that you set the timing knob at -3 , minus 3 degrees for the first time, maybe -5 if you're using less that C16 and + 3 on the fuel knob. 

   I would keep the WOT pulls at only 3 to 4 seconds to start with. You'll need to set the EGT gauge to read maximum cylinder temps and it will show only the hottest cylinder, which is most important. Go to WOT and keep an eye on the cylinder temps, either let up or add 5 % fuel if you see the temps going to 1100.  Adding 5% should bring the temps down from 100 to 150 degrees.  Go ahead and  adjust the fuel and do a couple more 4 or 5 second runs until the temps are close to 1050 max.  No need to keep track of the knob settings as they are logged to that  rpm site and are now a matter of record.

DATA LOGGING

   Now head to shore and we'll do the data logging. Hook up the cord and download data. Open a cool one and jump in the easy chair with your laptop.  Looking at the rpm graph and the fuel knob graph, go to where you made adjustments to make it run smooth. It;s probably the last run or adjustment  before you went to  another rpm area.  Make a note of the RPMs , TPS % , knob position and O2 reading. From this data you can go to the main engine program and make a calculated change at the proper fuel site. Calculations are made from the knob  percentage  values. No guessing on jet sizes here. Save the modified program under a new name, such as Rev 3, adjusted WOT fuel. and don't forget to load in the new program and set the knobs back to 0.  That's it , now your an EFI tuner.

     If you're not sure of  how the engine is running, just e-mail me the data log and I can look and compare graphs to my old ones and probably tell what is wrong or what needs changed.

238.7 hp at 7650 rpms