JetManiac/Blue 781 - backflip capable

Been meaning to post this for a while. I bought my first aftermarket hull this year. It’s a RCW Havoc and the first AM hull I’ve ever ridden. It came with a very fresh 781 from jetmaniac. The ski ripped, but I had no skill and wanted more power so I bought a 1015. Long story short, found metal in the 1015 shortly after I got it dialed in, so I switched back to the 781 “temporarily” (or so I thought).

Many unforeseen machine shop issues have made the 1015 rebuild a 10-12 week process. In that time, I decided I was going to learn to flip the 781. I’d say I attempted 100 or so flips before I got them all the way around. Most of those attempts were with the big motor prop (8/16 thin blade) so the setup was not ideal. I finally got it and can now land 1 out of 5 or so.

This jetmaniac motor is insane for its size. Everyone who rides it is blown away. It’s had probably 100 gallons though it this season or more and it’s never had an issue.

@JetManiac and @Blue do an incredible job for an incredible price. Not to mention Chris is extremely helpful and gets stuff shipped suuuuuper fast. I’ve dealt with a lot of jet ski companies and these guys are by far the best!!! Highly recommended.

Setup details:
RCW carbon havoc
781 by jetmaniac
38mm carbs
Zeeltronic ignition, slightly more aggressive curve than wax curve
PFP pipe ran wet. 67.5 spray bar jet, 90 in the stinger
Stock 155 pump
6/12 prop Repitched to 7/14 -5mm cut back
Limited slip tank
Thrust trim

I too can vouch for the JM781. It’s very cool to see completely different setups around the heart of the machine. This video is of a JM 781 in a heavy glass hull, 38s, MSD enhancer, PFP, and an oem 155.

@Jcary85 , how is yours on fuel? My woman can burn 5 gallons in just over an hour. Seems like it eats a ton with only 38s.

I've got a JM781 in my chan and love it. I've never ridden a +1000cc ski but I love the power I get from the 781 in combo with the torrent 148 setback pump I have. I'm currently only getting about 3/4 of the way around in my best attempts. Not the ski's fault, I'm just a chicken. The ski did make it all the way around on it's own once when my feet came out. I prefer riding barefoot but had to break down and buy some wrestling shoes, I'll post a video if I ever get it all the way around.

Thanks guys for the inspiration to keep trying!

Thank you for this post. Im glad to hear that you are happy with the motor. It would probably be even better with a smaller prop but by the looks of the video you are getting it done...

I was just tell Chris this weekend that i wish more people would try bigger carbs, more compression and maybe a little race gas rather than going to a bigger billet motor. The motors I build are very dependable, run great and have a lot of power with 38 carbs and pump gas. But with the bigger carbs and some other add ons like total loss theres no need for a bigger engine. There is still more power to be made in the 781 with the proper setup.

Thanks again.
Blue

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forgot to mention, I'm 5'10" and 210lbs. I'm not a small guy, so let it be known that bigger guys can flip too even with a relatively small motor!

Blue said:

Thank you for this post. Im glad to hear that you are happy with the motor. It would probably be even better with a smaller prop but by the looks of the video you are getting it done...

I was just tell Chris this weekend that i wish more people would try bigger carbs, more compression and maybe a little race gas rather than going to a bigger billet motor. The motors I build are very dependable, run great and have a lot of power with 38 carbs and pump gas. But with the bigger carbs and some other add ons like total loss theres no need for a bigger engine. There is still more power to be made in the 781 with the proper setup.

Thanks again.
Blue

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Click to expand...

I do have Novi 48s and a PHP intake laying around. Maybe i'll give it a go!

PS, I did run the 6/12 for a bit and felt it was under propped. Maybe its just because i was so used to having the wrong prop but i felt like i was taching the motor out before i was halfway through the setup wake and just couldn't get the thing around. I didn't give it very long though. probably needed some more technique change.

SmittySX said:

I too can vouch for the JM781. It’s very cool to see completely different setups around the heart of the machine. This video is of a JM 781 in a heavy glass hull, 38s, MSD enhancer, PFP, and an oem 155.

@Jcary85 , how is yours on fuel? My woman can burn 5 gallons in just over an hour. Seems like it eats a ton with only 38s.

Click to expand...

Mine SIPS fuel. Its amazing. Everything is relative, but compared to the 1015 with 48s, it burns probably half the fuel. On a weeknight, I'm out for about 2 hrs, probably 1.5hrs of actual riding and don't make it through 5 gallons. Maybe 4ish.

Blue said:

Thank you for this post. Im glad to hear that you are happy with the motor. It would probably be even better with a smaller prop but by the looks of the video you are getting it done...

I was just tell Chris this weekend that i wish more people would try bigger carbs, more compression and maybe a little race gas rather than going to a bigger billet motor. The motors I build are very dependable, run great and have a lot of power with 38 carbs and pump gas. But with the bigger carbs and some other add ons like total loss theres no need for a bigger engine. There is still more power to be made in the 781 with the proper setup.

Thanks again.
Blue

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Click to expand...

What would your ideal setup be to get the full potential out of the 781?

I think a 781BB with a
PFP or RRP style pipe WET. With a Ported exhaust manifold.
Novi 48s maybe even 49s
V Force Reeds 2 or 3s.
A good intake manifold
Compression in the 220 to 235 range
Total loss with an aggresive curve would ripp pretty hard.
If someone was planning a build with the intentions of doing a setup like this I could possibly even do a little more on my end to ensure it gives max potential.


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Congrats again buddy. The ski is a good machine but I know its your dedication and effort that made it come around for you. You can see how hard your working for it!

I'll chime in on the JM/Blue 781BB as well. Mine is in a plain old 2004 SJ with all the typical goodies B Pipe, MSD , Lightened flywheel, etc. etc. and it absolutely rips thru the entire powerband. If I don't consciously remember to hold on with a death grip when I pin it, it pretty much leaves without me. And the funny/surprising thing is that not only is the acceleration like flipping a light switch, but the top end is white knuckle scary now. I greatly enjoy when the clowns on their Sparks come around to 'play' and I just leave them behind choking on two stroke smoke.

SXIPro said:

I'll chime in on the JM/Blue 781BB as well. Mine is in a plain old 2004 SJ with all the typical goodies B Pipe, MSD , Lightened flywheel, etc. etc. and it absolutely rips thru the entire powerband. If I don't consciously remember to hold on with a death grip when I pin it, it pretty much leaves without me. And the funny/surprising thing is that not only is the acceleration like flipping a light switch, but the top end is white knuckle scary now. I greatly enjoy when the clowns on their Sparks come around to 'play' and I just leave them behind choking on two stroke smoke.

Click to expand...

My new favorite term.. is it fast bro. No its White Knuckle Scary ...

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@Jcary85 do you still have the curve info? I'm about to put TL on my jm781.

Power factor, oem 44's on php intake, 185psi, oem 155 pump in a glass phantom. Almost getting back to back flips in, this should put me over the edge!

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I don’t have the exact curve but its pretty simple - run 14 or 18 until 1500rpm. 32 degrees from 1500-5500 then taper to about 21 at 7000 and down to maybe 7ish at 8k - 8k rpm limit. You'll love it! zeel is great! i just switched back from MSD TL to zeel and have no regrets and no failures.

PS - you could probably up the timing a bit if you have good gas or run a bit of race gas mixed in for safety (but blow up your motor at your own risk )

You ran this with pump gas?

It's that really 7 at 8k it should it say 17?

Actually now that I think about it I ran a 1/4 race/pump mix. Ya, 7 at 8k. Retard helps heat the pipe I’m told

I was also running 215 psi domes though. I do think it would be safe on race gas. I know other guys running pump gas setups with 32 total timing.

I'm running the original wax curve in a pump gas motor right now, and that peaks at 32 but it backs off a lot faster than the curve you posted. It's an interesting point of reference.