2007 Optimax 200 MercMonitor reading about 350n RPMs less than Analog Tach

[dmherron]

2007 Optimax 200 1B458995 Runs great no issues that i know of how ever i installed a MercMonitor gauge last year, and noticed on the MercMonitor that the max RPM i could get is 5370, but on my analog gauge it is bumping up just below the 6k reading. Is there any way to know witch one is correct? this is on a 2007 Procraft 200 Super pro, I get the same RPM with a 3 blade 24 pitch prop or a 3 blade 25 pitch prop, I do pickup about 4 MPH with the 25 pitch.

Thanks much

[06 SB]

The Mercmonitor RPM is straight out of the computer. It is the correct reading. Limiter I believe is 5750 so no way you are getting up to 6000 regularly without an alarm.

[Savage]

If you can only get 5370 RPM'S, then you are running too much pitch. Prop the boat to get 5700, that's were you make the most HP. 5300 is lugging the motor.

[SilverFox579]

+1 to both replies above.

[EuropeanAM]

+2 to both above replies.

[dmherron]

OK so as my first post said I had a 25 pitch tempest that gives me 69mph at 5370 RPM, I dropped down to a 24 pitch and RPMs did not go up at all but speed dropped to 65, I have now tried a 23 pitch RPM still max at 5370 but speed is now down to 62Mph.
This has got me confused. These Rpm readings are from the MercMonitor. Motor does not have any other issues that i know of, it has me thinking it may be fuel related so i went ahead and changed the fuel line and bulb with the Mercury replacement, according to the MercMonitor I have 10.3PSI fuel pressure.

I am lost, Is it possible that the rev limiter got changed during a service,(by accident)?

Any help would be great.

[SilverFox579]

You can disregard fuel pressure because it is NOT monitored for Optimax. Go into settings and turn fuel pressure off (I did).

[Savage]

Rev Limiter can NOT be "changed during Service". Are these known good props that you are trying? Are you adjusting the trim with each prop change?

[dmherron]

Yes both the 24 and 23 are new from dealer. Yes I have hydronic jack plate have even raised it up and trimmed all the way up. Trying to get the motor to reach max RPM.

[EuropeanAM]

Need to go back to the basics- Compression, SPARK and Fuel Quality/Delivery/Air-Fuel Pressures.

If no problems are noted there, and NO FAULTS are occurring, it may be necessary to perform a Cylinder Misfire Test @ WOT (on the water) with the Computer Diagnostic System. Record RPM drop for each cylinder.

[dmherron]

Thanks Don have done the basics compression is between 110 and 108 on all six, I did have a spark issue and found a faulty coil driver found it buy using a timing light it was causing a mis on #3 and #5 cylinders, it was replaced that did let me get up to 5350 rpm, I think I may have found fuel issue after double checking fuel and air pressure and confirmed they are within spec, I pulled in fuel injectors and found #5 has some damage to the small o ring that seals in the air injector.

when the rain stops and I get to test I will let go know if a new injector fixed it.

The o ring was intact just crimped and I don’t think it would have sealed good.

[EuropeanAM]

Both o-rings on the Fuel Injectors seal them to the Fuel Rail (not the Air Injector).

Definitely replace the o-ring and see if problem persists.

[dmherron]

Well got out on the lake today, mercmonitor still showing 5370 as max rpm. Motor runs great no miss at all jumps up on plane. Can not get it to hit the reg limiter at all. Changed all fuel filters checked pressure they are good about 9.8lbs difference. This sucks

[EuropeanAM]

Has this engine, in your possession, with either of the above current props, EVER reached 5700 RPM's on the Smartcraft Instrument?

If not, let's get an abbreviated history of the setup/origin and what info you do know.

[dmherron]

Don,

[EuropeanAM]

Yes... believe you are replacing some reeds?

[dmherron]

Hey Don, I just wanted to say thanks much!!!! Yes looks like I have a couple of chips, and several that are not closing all the way. I can not tell you how much it means to have someone to help us out. And I know I will always support you with my business!!!!!

i will update motor stats once new reeds are installed.

[EuropeanAM]

[dmherron]

Don, you are the MAN sir got the reeds today, have them installed along with a fresh set of plugs. Engine fired right up idle is great. I will get it out on the lake this week and let you know how it runs! Hoping to s e RPM up around 5700 or so.