300X?

[Matt Wayne]

I have a 2003 300x (0T652837) and alot of the times after the motor is up to temp it wants to die when you put it in gear. It idles around 650-700 rpm according to the merc monitor. It starts and runs great but its just annoying when fishing a tourn and I half to put it back in neutral and restart it. I thought at first it could be the tall 1.62 gears and a 27 pitch prop but wandering now if it could be something else.
Thanks
Matt

[Largemouthlou]

There is a relay that is supposed to idle it up a touch when shifted into gear I believe. Sounds like it just needs an adjustment, it isn't the gears or prop

[EuropeanAM]

Idle speed is PCM CONTROLLED on this engine.

A couple of possible causes:

-Shift position switch malfunction
-TPS malfunction
-MAP malfunction
-Inadequate throttle plate air gap (due to wear)
-PCM calibration problem (there have been multiple calibrations, with variations in idle RPM).

[Largemouthlou]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by EuropeanAM &raquo;</td></tr><tr><td class="quote">Idle speed is PCM CONTROLLED on this engine.


-Shift position switch malfunction
- </td></tr></table>

That is the one I was thinking of

[Matt Wayne]

Thanks guys. I will check the shift position sensor first.

[mark21xdc]

Mines a 2004 300x and does the same thing as yours, just got the service manual from Don, I'll check those also.

[Matt Wayne]

Let me know what you find. Ive been out of town this week so I haven't had the chance to work on it. Maybe next week.

[mark21xdc]

Soon as I look at it, works been crazy!

[gofastallison]

wow; my first time to visit bbc; did not know other owned 300x's; mine does the same thing but my most serious problem is fouling champion plugs; appears to be running too rich? if i run high speed it is not as bad; i checked all the sensors Don referred to with an ohm meter; all checked ok? good luck

[EuropeanAM]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by gofastallison &raquo;</td></tr><tr><td class="quote">wow; my first time to visit bbc; did not know other owned 300x's; mine does the same thing but my most serious problem is fouling champion plugs; appears to be running too rich? if i run high speed it is not as bad; i checked all the sensors Don referred to with an ohm meter; all checked ok? good luck</td></tr></table>

Welcome to BBC!

What gap are you running your plugs at (and if you can, confirm WHICH Champion plug you're running).

[Nikon Man]

Various RPM idle stages have been given to the 300x over the production years, 650 RPM (newer years) to 800 RPM (older 2001 model), now please note that this is "<u>AN IN GEAR IDLE</u>", <u>and not a neutral idle speed</u>. I've seen guy's try to set the idle in neutral to these speeds and that will cause extreme damage to the gear case when shifted into gear. Just an FYI........

From my past experience on the 300x when dying at idle, usually indicates that it's running rich and injectors should be considered as a possible cause after you've checked that the shift position switch is working properly. The 300x tends to load up quite fast when put through long periods of idle time, as an example engine warm up, where your running rich anyway because of the ECM control setting a rich condition for warm up and if your injectors are running fat, that just compounds the problem as the plugs start to load up/foul. That usually noted when you attempt to get on plane and the motor blubbers until it cleans itself enough to fire cleanly...........

[gofastallison]

thanks a lot for your fast respondance; running Champion QL77PP per service manual set at .025; have tried NGK BR8HS and BUZ8H; BUZ made one fishing trip and then would not start day of tournment; put Champion back in and ran high speed all day; days end plugs 1,3,5 looked like wet fouling had started; number four normally fouls out at 3000 plus or minus RPM. thanks for help opps got post crossed; replies to Nikon Man and Don ---
Nikon Man is distribing what is happening to me;

[gofastallison]

don; sorry; send reply to wrong post;

[EuropeanAM]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by gofastallison &raquo;</td></tr><tr><td class="quote">thanks a lot for your fast respondance; running Champion QL77PP per service manual set at .025; have tried NGK BR8HS and BUZ8H; BUZ made one fishing trip and then would not start day of tournment; put Champion back in and ran high speed all day; days end plugs 1,3,5 looked like wet fouling had started; number four normally fouls out at 3000 plus or minus RPM. thanks for help opps got post crossed; replies to Nikon Man and Don ---
Nikon Man is distribing what is happening to me; </td></tr></table>

Try bumping your plug gap up to .035" and see how it does.

I would, however, STRONGLY recommend that you have your injector cleaned, flow tested, and calibrated.

The pink-tipped Keihin injectors are NOTORIOUS for flooding problems.

http://www.europeanmarine.org/injectorservice.html

[gofastallison]

Will set gap as recommended; Motor is an 05 and it preforms difference than when was new; will do injectors also; is ohm test actuate on sensors and do you see any need to do DDT TEST for other problem?

[Nikon Man]

Ohm test will do just fine........I feel your pain James, been there.....done that, I speak from experience.... ....good luck.

[gofastallison]

thanks for reply; my problem is i fish and like to speed however fishing you may only move 300 yards and do not get motor and plug temp up; of course you know what is going on; it so serious i am debating on 250 proxs; 300x likes gas but by time you weight difference in other cost do not know if pay out there?

[Nikon Man]

I here ya....... The 300x IMHO was never designed to be a fish'n motor and hell ya it loves the gas. But in all honesty, from what I've seen posted and heard I personally would never invest in an "XS" motor. They still have to many issues, now I'm not saying all motors and on a positive note, sure they sip the gas. When they go out and your out of warranty ya better have deep pockets..........

[Largemouthlou]

Gary, no disrespect! But in my experience with my 300X it fishes very well, idles through no wake zones great and dosen't mind running slow for the passenger seat rev limiter.

Yes it will fowl just a touch with 10 miniute no wake zones but fuel additives help with that. That has been my experience with my motor to date.

[gofastallison]

thousands questions; i am you; how many hours on yours; type of plugs, gas, additive, oil, boat, prop, tips to correct my problem; i am gathering any input i can; thanks