800 Enhancer Set Up

[Watercraft Magic]

HydroX,
Your timing chart is correct for the 780 motor according to TSR software.

55, the oem timing is to be checked at 3500 rpm. It is no suprize to me that you are reading 18 degrees at 2000 rpm, as the oem charts mostly show 19 degrees at that rpm. Also, the oem electronic correction maximum is +3 degrees using the #2 correction factor on the Sea Doo programmer.

[hydro X]

I`m at 19.5 ish on mag, and 20.25 ish pto. base timing no mpem.
This has got me thinking though and about to try a low comp ( 180 psi ) with a D pump and no grate. And some real race fuel.. hahaha.

[427racing]

Alright, so let me get this straight. 1. I find the TDC. Which I have marked on the PTO. 2. Using tape or measuring I mark the degrees on the pto. 3. Set the ehancer on +0 to get the initial timing at 3500rpms. Say it shows 19 degrees. Do I want to anvance until I hit 22degrees? I have a Mod engine, so do I want to hit 24? And from there am I retarding 7 degrees to get back to 17 for overall timing. Am I even on the right track here? Thanks

[Watercraft Magic]

Yes, you are on the right track and if it is a mod motor on race gas, then 24 degrees will perform better than 22 degrees. I sometimes go up to 25 degrees and even 26 on the right setup, but I bring it back to around 15-16 degrees at wot.
BTW, you understand about measuring back on the pto? You do it with a dial indicator in the front sparkplug hole. Do not measure back on the pto from the TDC mark, but mark the pto when you get the desired rotation of the front piston as measured with the dial indicator.

[Radical337]

Yes, that is exacty the curve I use with good fuel as well: 25 initial, retard start at 5000, 8000 rev limit, 12 degrees total retard. This yields exactly 15 degrees total advance at 7500 RPM.

[holmes99]

ttt

[a1965gt]

Bump for tons of great info

[Junk#52]

Degrees Crank Rotation = Piston position from TDC in mm

30 = 6.185
29 = 5.793
28 = 5.413
27 = 5.044
26 = 4.687
25 = 4.343
24 = 4.01
23 = 3.69
22 = 3.382
21 = 3.087
20 = 2.804
19 = 2.535
18 = 2.279
17 = 2.035
16 = 1.805
15 = 1.589
14 = 1.386
13 = 1.196
12 = 1.02
11 = 0.858
10 = 0.71

The factors that you must consider is the stroke and rod length
If anyone has a way of checking these measurements, it would be greatly appreciated, as these are the ones I am currently using.

So I have a Mel Miller with a lightweight PTO on it just read through this whole thread.. are these the right numbers for a 787 engine?

[JC-SuperJet]

Those are the TSR Software numbers and they don't match Seadoo's and Bill O'Neill's Numbers...

For example, Seadoo says 21 degrees from TDC is 0.113", which is 2.87mm, The HydroX Chart shows 3.087mm for 21 degrees; definitely not the same...

Or, 25 degrees from TDC is 0.158" is 4.013 mm, but HydroX shows 4.343 mm, also not the same.

What many miss is that the Ignition Pick-Up is not installed in the perfect spot, it is always a few degrees off from the Factory. So each 787 Engine comes with slightly different Static Ignition Timing. A few degrees off up or down. Seadoo chose to correct this at the MPEM.

When you install a different MPEM or Programmable CDI like MSD, Advent or Zeeltronic, you need to find your Ignition Timing at 21 degrees by marking the PTO at TDC at Zero inches Dial Indicator, and at 21 degrees from TDC at 0.113" from TDC with a Dial Indicator. Then using the Timing Light and correct Timing Tape, you can see how many degrees off from 21 degrees that Pickup is.

Then you compensate for this excess Advance or Retard (Subtract or Add) at the Programmable CDI.

So, if the Pick Up is 4 degrees too Advanced, you need to subtract 4 degrees from every number on your Timing List, unless the CDI has a programmable feature which automatically does this throughout the whole rpm range.

See the Seadoo Manual Ignition Timing Procedure and the Advent Timing Calibration Procedure.

The Seadoo Numbers are for a STOCK Engine. A Modified Engine with different Base Gasket, Head Gasket, Milled Head, etc will affect/change the Piston Distance from TDC versus Degrees Rotation...?

[JC-SuperJet]

Same Stroke, then Piston will travel same distance with each degree Rotation. The Dial Indicator will be Zeroed anyway at TDC, so the Distances should be the same...