Exhaust/cyl head temps??

[STEVE FRENCH]

Steve:

Do you find a better reading with the exhaust probe that far off the port? I've always kept ours at a bout a 30° to the top port between the first and second spacer bar. My thoughts were to get the probe as close to the internal parts making heat as possible, not to give the gas a split second to cool down....

Any thoughts?

Skoontz, Here's a closer pick of were I located mine.....not sure of loss af accuracy at this location but I guess for me it's all for comparison from one adjustment to next and how it feels on race course.....

put dial indicator in my late model 500/50hp merc with CDI and degrees on flywheel and kind'a surprised at degrees at .300 btdc on dial!

Brian, Thanks for link on Digatron....wow, cost on the DK-53 series!...But then again melted parts add up fast!

Tom Cronk added to the 25SS skeg...it still needs some finish/shape work...but have raced it and never "broke loose" with this length...probably some extra drag with this length but anything that keeps me from cartwheel'n at 70+MPH is worth it...that foot has 1x1 gears and try'n some of my 15ci Hot-rod and 302 Yamato (15x16 ratio) wheels on it.....wheel in pick is a small OMC-A wheel that worked somewhat with chamber ...but still a slug in corners with chamber on this deflector piston motor.

19P

[bh/]

timing?

Steve; -get back in your box and quit thinking so much. You are disturbing people.

i)ask Bette[?] at Digatron to give u the number for their field engineer who is based in MI.
He is quite interestd in o/b's, and was great help to me in getting a tach to work on old
4cyl Merc mags.
ii) most all two strokes will give more torque at mid rpm's with advanced timng, but will not stand this timing[heat] at full rpms for long. Do what the old DSH racers did. Set the throttle to give full carb opening and say .300" BTDC at 2/3 throttle . Then set it to give say .350" BTDC
at full throttle. Run out of the corners at full throttle, but back the adavce off half way down the straight. The exhaust gas temp will tell
you when to do this.
Some one a lot younger and smarter than us could bread-board a circuit that would integrate timing and exhaust gas temp and set max advance automatically.
But that would be no fun.
Hope to see [hear] this monstrosity at Waterford, ON in June.

[johnsonm50]

Skoontz, Here's a closer pick of were I located mine.....not sure of loss af accuracy at this location but I guess for me it's all for comparison from one adjustment to next and how it feels on race course.....

put dial indicator in my late model 500/50hp merc with CDI and degrees on flywheel and kind'a surprised at degrees at .300 btdc on dial!

Brian, Thanks for link on Digatron....wow, cost on the DK-53 series!...But then again melted parts add up fast!

Tom Cronk added to the 25SS skeg...it still needs some finish/shape work...but have raced it and never "broke loose" with this length...probably some extra drag with this length but anything that keeps me from cartwheel'n at 70+MPH is worth it...that foot has 1x1 gears and try'n some of my 15ci Hot-rod and 302 Yamato (15x16 ratio) wheels on it.....wheel in pick is a small OMC-A wheel that worked somewhat with chamber ...but still a slug in corners with chamber on this deflector piston motor.

19P

Ive heard 16:21 to be the choice for B1 but who can argue if you win? Again.. heard 16:21s wont la$t long, and the 1:1s are a little tuff-er. Id guess its in the props you run that make it go as much as anything else.

[STEVE FRENCH]

Steve; -get back in your box and quit thinking so much. You are disturbing people.

ii) most all two strokes will give more torque at mid rpm's with advanced timng, but will not stand this timing[heat] at full rpms for long. Do what the old DSH racers did. Set the throttle to give full carb opening and say .300" BTDC at 2/3 throttle . Then set it to give say .350" BTDC
at full throttle. Run out of the corners at full throttle, but back the adavce off half way down the straight. The exhaust gas temp will tell
you when to do this.
Some one a lot younger and smarter than us could bread-board a circuit that would integrate timing and exhaust gas temp and set max advance automatically.
But that would be no fun.
Hope to see [hear] this monstrosity at Waterford, ON in June.

Hey Brian.....I may need a rope'r!! .....Was kinda cool win'n the one heet of BMH there a couple years ago.....Gonn'a try to git back there this year....hear it should be a GOOD time!

have looked at my old Desilva throttle with pipe puller to run adjustable mag instead of the fixed.

Disturb'n.....might make a good boat name.....A?

19P

[STEVE FRENCH]

Ive heard 16:21 to be the choice for B1 but who can argue if you win? Again.. heard 16:21s wont la$t long, and the 1:1s are a little tuff-er. Id guess its in the props you run that make it go as much as anything else.

Just had a long talk with my motor Wizard/Rick Morris and he said same thing.
Have just got to were I'm run'n some monster sized wheels with 16/21's and the 14x19 OMC/Hot-rod foots......so was think'n of Merc 1x1's or Yamato 14x15's with a pro-foot and run a wider course to hold speed.

Well, time to git back in my box and git back test'n

19P

[johnsonm50]

Just had a long talk with my motor Wizard/Rick Morris and he said same thing.
Have just got to were I'm run'n some monster sized wheels with 16/21's and the 14x19 OMC/Hot-rod foots......so was think'n of Merc 1x1's or Yamato 14x15's with a pro-foot and run a wider course to hold speed.

Well, time to git back in my box and git back test'n

19P

You can use a Yamato pro foot in B1 mod??

[STEVE FRENCH]

You can use a Yamato pro foot in B1 mod??

When you say B1....Are you refer'n to AOF/NBRA or APBA?
APBA opened up to foots that meet R/S and ratio specs in 25MOD but are hold'n the 22 motors in B to specs when they were crossed over...I would not go near B with a updated motor......that's why I'm test'n with Merc 1x1's to see if I can get close to my best 16/21 wheel that I lost a few years back.
Got a couple small 302 wheels that may work but loss of "punch" may be a lost cause.......

Here's some read'n material....
https://hydroracer.net/forums/showthread.php?t=9931

https://hydroracer.net/forums/showthread.php?t=6713

https://hydroracer.net/forums/showthread.php?t=12735

Kind'a disturbing huh?..................

19P

[Mike 41P]

OMC25 timing

I have a whole table on degrees versus stroke.
Here are some, you can believe you melt pistons at 360!
degrees position
26 154
28 177
30 201
32 227
34 254
36 283
38 312
40 344
42 376
44 410
mike t

[johnsonm50]

When you say B1....Are you refer'n to AOF/NBRA or APBA?
APBA opened up to foots that meet R/S and ratio specs in 25MOD but are hold'n the 22 motors in B to specs when they were crossed over...I would not go near B with a updated motor......that's why I'm test'n with Merc 1x1's to see if I can get close to my best 16/21 wheel that I lost a few years back.
Got a couple small 302 wheels that may work but loss of "punch" may be a lost cause.......

Here's some read'n material....
https://hydroracer.net/forums/showthread.php?t=9931

https://hydroracer.net/forums/showthread.php?t=6713

https://hydroracer.net/forums/showthread.php?t=12735

Kind'a disturbing huh?..................

19P

Well yeah.. disturbing how much there is to learn, lol APBA reg 3 is where Im interested.

[Mike 41P]

my new omc25

just started it first time yesterday, at least it runs, put 45 minutes on it, dry land, in the driveway
hope to find out at Franklin if this pipe has any guts
its taken 4 years since I decided to try a chamber to get to here
Mike T

[STEVE FRENCH]

Wow Mike!

Sure some time invested in that one.....With the slider you might have more low end than my fixed pipe..
Can you change stingers? I have found a large opening with the deflector motor seems to help.....wound up with a 1 1/2" opening....Still would like to try slide'n it.....Gett'n on plane no problem but once prop hooked up it fell on it's face till up to speed and then pulled hard once on-the-pipe......sure wish there was a 2-speed or variable prop avail..........

See Yaaaa Friday-Franklin
19P

[STEVE FRENCH]

So is 32-34 degrees the prefer'd advance on a CDI motor?

Might git back to some test'n with my 25MODS

Any other interest in the class?......... or is it ex-stink't?