640LX 90opti

[Mike Nelson]

Hi guys,



I have a 640 with a 90opti currently running 51mph in the right conditions with a laser 2, 22p prop. Motor is on 2nd highest hole. (tried it on top and no good to high)

I am soon to get the ecu tuned to 120hp. however 1st i am adding a jackplate. Should i go for a 6" model or a 4"?



Thanks for you help.



AUSNITRO

 

[Bob Bourget2]

If your steering cables and "rigging" allow the extra set-back, I would go with the 6". Just curious......who and how are you getting the ecu "tuned to 120 HP?". There are other "restrictors" in place on that engine, prohibiting the gain you hoping to achieve.

 

[TOMMY RICH]

Settin' back eating my popcorn.....:unsure:

 

[Dan J.]

Reflashing the outboard ECU has become an increasingly common mod. for years now. If warranty and cost are no concern, then I imagine it could be fun to wind it up and see what gains are added with the lighter weight engine on a lighter rig. (I would suggest an EFI or carbed powerhead would be a better choice over a DFI engine for the additional concerns Bob mentioned.) I agree with the 6" jack to give more performance on that smaller profile, but you may want to disconnect your tiller rack and pull the steering rigging out and see if new cables/hose may be needed before getting the jackplate on and finding the need. Good luck and let us know how it goes, mate!

 

[Bob Bourget2]

Agreed. I've had ECU's re-flashed by Rapair to raise rev limit {11,500RPM} on my drag motors. They do a great job.

My question was and still is......how do they plan on getting "120hp", out of a PCM re-map. The throttle body / reed block / reed must be changed as well......

 

[fatrap]

Man Ausnitro how fast do you gotta go to outrun those "Salties"?



fatrap

 

[byron cooley]

Hey Austin - Let us know how the "repaired" ECU works out for you. I have talked to Simon also and the limiter can also be bumped up to 6200 without issues. Mine is out of warranty so I should be doing the mods around July.

BOB - 120HP has been dyno'd with only the re-flash and removing the throttle body restrictor. I believe the reed plates are the same part # for the 90/115hp's.
http://simonmotorsports.com/

 

[Dan Nevill]

Ausnitro,



I havew the same boat and a 90hp on it. Let me know what you had to do, what it ended up costing you (mods and jack plate) and if it really worked once you test it. I'm interested in doing the same mod if it works.



Dan

 

[Mike Nelson]

Hey guys thanks for the feedback, reason i was considering a 4inch setback is that it would introduce less stress on the transom and the fact that the 640 with a opti is allready stern heavy and has a slow holeshot. I didnt want to move the weight too far back.



Would the 4 inch and 6 inch be any different performance wise?

Oh and btw i have Hydraulic Steering.







FATRAP: no salties where i am just lots of bullsharks, no swimming. :0



DAN: I guy i know has done the upgrade, he has a 640, 90opti with 6inch plate tuned to a 120hp with a 24 or 25p 4 blade he is running 56mph probably a little more unloaded.

 

[Bob Bourget2]

Reed plate / reeds are the same. Different for the 125. Throttle body size MUST be changed...

 

[Mike Nelson]

So i am going to need to get a 125 throttle body when i upgrade to the new 120hp tune ?

 

[Bob Bourget2]

No, just the restrictor must be changed. If you want the "most", contact Simon and he will steer you in the right direction. Ask him about reeds.....

 

[Mike Nelson]

Bob B,



Could you give me a run down on what i can do to my motor.



I thought all you could do to a 90opti was to put a 120hp tune in it and remove the throttle body restrictor. What is the talk about reeds?

 

[Bob Bourget2]

The 75/90/115 reeds / reed blocks are different than the 125. The 125's set-up is obviously designed to flow MORE. When you speak with Simon....inquire. If you're going to pony up for the re-flash, etc., why not go all the way?

 

[Mike Nelson]

Fellas got my jackplate on, no engine tune just yet. Thought i would update you one my progress.



I installed a Vance 4 inch plate.



PROS:

* Seems better holeshot

* Much better at speed handling

* Boat does not list to the left anywhere near as much running at slow speeds or getting on and off plane.

* Prop bites better

* Speed increased a little boat now just hits revlimiter at 51.5mph with just me and half fuel. Sits right up on pad.



CONS:

* More backwash when dropping off plane.

* only just fits in my shed!





So it appears the 640 does benefit from a plate. Mind you i dont know if a 6" plate would improve this more or actually reverse my results. What do you guys think.



One more question, my laser 2 is a little dinged on the leading edge, would getting this prop tuned gain my anything ?



Specs on boat: 2005 640lx, 2008 90HP Optimax, 22p LAser 2, 4" vance JP. 51.5mph at 5800RPMS light.

 

[Bob Bourget2]

YES. Contact Mazco propeller, ask for John, tell him I sent 'ya......1-636-343-9911

 

[Mike Nelson]

Back fellas. Considering my next upgrade. What prop should i chose when i get my engine tuned to 120HP. Should i run a laser 2 or a trophy plus. What will give me the most speed?



Also what height should my prop shaft be at with my new 4inch jackplate ?



thanks



AUSNITRO

 

[Bob Bourget2]

Experimentation with your specific "set-up" is the only way to get 'er done. Each and every boat is different. I took a customer for a test ride in his Z-9 / 250 ProXS the other day since he was complaining of only 60-62 mph. Noticed he was running a 26" Fury...and....he loads the boat up with the entire stock of goodies from BPS. Pro-pole. Add that to the full livewells, full tank....two 200+lb fishin buddies and you get the picture. Before I even launched it, swapped props out with a new 24" Tempest, knowing it is over-propped. Personally, I was on and above the limiter at over 6000rpm, and better than 70 GPS MPH. It would go FASTER with more pitch. With him in the boat, ran 67+ at about 5800rpm. To get there, required constant fiddling with the jackplate and trim. I know the prop for solo use is too small...but that's not how HE uses it. Moral of the story.....based on load, operating conditions, set-up, etc might require UNCONVENTIONAL choices. Experiment with props, motor height and weight distribution to achieve your personal best.....let us know when that happens. Be sure to monitor water pressure and rpm, and keep within spec parameters.