Promax vs. lazer efi

[Vecman]

I'm trying to understand the difference a promax and a
reg efi bass boat motor also known as a lazer type
efi. Why can a promax turn 7400 and a lazer turn 6400
at rev limit. Is the fuel system not the same? Are the
pistons and rods not the same? Any answers are welcome!
Just trying to learn the difference.


83' Vector
200 merc

[half fast]

Promax 2.5 liter motors use the (Laser) type efi.There are only three types merc uses,direct injection on the clean optimax motor,laser type for quick starts and good acceleration and the crankcase type injection found only on the hot rod motors.Not sure why you say a promax will spin 7400 and a laser will spin 6400 they are the same.Maybe a different rev limiter or just plain horse power. Most promaxes are limited at 6500 to 6750 rpm at the factory but this can be removed . hf

[Tony Brucato]

Actually the PoMax factory rev limit is 6750 (some are only 6450)
You can turn these motors 7400 rpm by having the rev limiter removed by Rapair. Removal of the oil injection would be a must at that rpm, as well as converting to a lightweight flywheel.
The fishing motor version would only lack the Boyesen reeds to have the same reliability as the modified ProMax. The cranktrain ( crank, pistons, and rods) would be identical on the two motors. The cast pistons should be safe up to 7500-8000 RPM.

Tony

[RED ALERT]

Anybody know which versions have the 6450 rev limit?

[Tony Brucato]

I've seen both versions on the same model and year. I don't know if it was by design or substitution for other reasons.
I've also seen some stock boxes turn over 7000!

Tony

[pirogue]

I think the old analog may not have a rev limit. I have a 94' 200 promax that came with an A20 no limit but, was removed by dealership before i bought it second hand and a digital was put on. don't know the #'s but was limited to approx 6750. i would see 7000 but not sure of accuracy.

[PFord]

Some of the differences are: 225 ProMax has 14 petal reed cages and different porting in the motor, most of those come with a 6750 rpms limiter. The 200 ProMax which is no longer made has the 10 petal reeds and a little different porting than a 200 EFI. I think in 1995 the 200 EFI went to an 8 petal reed cage and the earlier ones except the 1991 were 10 petal. The 1991 had 14 petal reeds. Mercury went to the digital ECU in late 1995 so if you have a 1995 you could have either, the one prior to 1995 were Analog. I have a 1993 XRi and have turned it up to 7000 rpms and never felt the liiter so it may not have had one. Hoipefully this will answer some of your questions.

[vishus]

my 93 XRI will turn a 26 chopper 85+ on GPS @ 7200rpm (about 10% slip) on my 94 RIOT. Stock ECU, stock motor other than reeds, no liner, exhaust relieved in lower.

I am not out of motor, I just haven't been able to go faster without my boat porpoising. I am goin out this afternoon to see if I can drive it with a Mazco RE4 26 (maybe it will be easy to handle than the Big Ear Choppers I normally run...)

my motor is running great, I am a little concerned that my rpms may bit a bit high for a steel flywheel.

do I need an aluminum flywheel or would that really come into play if I am hitting 7500+rpm?

thx.sid

[PFord]

Might be a good idea, and it will make your motor last longer.

[vishus]

thanks...

[Vecman]

I have a 96' 2.5 200 efi. It hit the rev at 6400. Just like hitting a
wall. A friend of mine has 2000' 225 Promax that runs up to 7400.
He didn't say he had the rev turned off. I thought he said his
limit was 6750!!! But he can spin a 26" 7400 rpm's. Maybe the
dealer turn it up not sure. By the way his oil injection is not
bypassed. I was just thinking that if his motor parts are the
same then it shouldn't hurt to turn mine 7000's with a reburn.
Without any major part changes. Thanks for all the reply's.
I'm still learning about the efi's. Thanks again for the information.
by the way with the high dollar fuel injection system these motors
have why bypass the oil pump? As far as I know these pump
do not have plastic gears as the old one's did. Maybe scared
of the pump keeping up?

Thanks again
vecman

[PFord]

If the ECU on the ProMax is stock I doubt it will turn that many rpms. What kind of speeds is your friend running with the 26. Another thing to consider the gear inside the motor for the oil injection is plastic and could fail the gear on the oil pump is metal, and we all know what happens when it fails. If you are planning on turning 7000 or more rpms you should remove the oil injection and pre mix because if you don't your asking for trouble.

[Rapair4]

Rev limiters in 2.5 XRi and Pro Max motors both go RICH at whatever RPM Mercury set it at. A 225 Pro Max hits a 40% rich wall at 6750. A analog ECU goes rich in steps so some motors can turn more rpm by burning off excess fuel. If any 225 Pro Max turns 7400 it has a higher rev limiter.
Sean Hill
EFI Engineer
CDI Electronics

[PFord]

Glad to see you on here Sean. I have 2 analog boxes if you want them. I work in Huntsville so if you want them let me know and I can drop them off.

[Vecman]

Thanks Sean and everyone else for all the info.
I plan on having the rev limit set up and changing
the reeds along with removing the oil injection.
I really don't want this motor to turn pass 7400.
I hear alot of people saying to remove the limit.
Do alot of people set there rev limit to their spec
or just remove it. One more question what cc heads
will bump compression up to 145psi. The motor
is stock and has 120psi now. Thanks again for all
the info.

Vecman

[Rickracer]

...even on a fairly light boat like a Vector. If you are certain that you'll never get a bad tank of fuel, you should be OK, but there's always the chance that some slackjawed tanker driver will dump the wrong fuel in the wrong tank and there you have it, saute'd pistons. 135~140 is safer. Reeds are good, removal of the O.I. is good, and you won't notice that much difference between 135 PSI and 145 PSI . :cool:

[PFord]

35cc w/thin gaskets or 34cc with standard gasket should get you real close.

[Vecman]

Thanks Rickracer, point well taken!
Thanks Pford for the info.

Vecman