300x Low on power issue

[Hydrilla Houndawg]

I got a guy who's 2005 300x sporty 1.62's seems to be slugish in my opinion. He is running it on the same brand boat I had with the same set-up that I had and is 10mph slower. I turned a 26 Bravo to 6700rpm @ 92mph. He cant put a 25 Trophy over 6300rpm @ 84mph. I drove his boat to see if it was driver and had the same results. In my boat with the same set-up you could stab the throttle and it would tweek the boat or torque to one side. His you get nothing. It feels like you are running a 34" prop and it slowly builds rpm and speed. Feels like it has NO BALLS... DDT shows nothing wrong. Motor idles and runs fine just seems to have no balls.

Could it be a bad sensor that the DDT is not picking up? Maybe a bad ECU? Anyone know of a dyno that can run a 3.0 in South Florida. I was thinking that maybe a dyno would show it low on power. We are running out of ideas??? Any thoughts?

[Stitch King]

Don't mean to restate the obvious....

Does it have a full 13.6+ volts? The coils need all the juice they can get.
Compression?
Plugs? Get rid of the champions and use NGK br8hs.

[THE HOGG]

when did they stop putting the $hitty coils on?? does it have the ones with the gray wires?

[Hydrilla Houndawg]

Don't mean to restate the obvious....

Does it have a full 13.6+ volts? The coils need all the juice they can get.
Compression?
Plugs? Get rid of the champions and use NGK br8hs.


Yes volts read out correct. New plugs, compression and leak down done. Been running champions. Was told by many that there is no correct cross over to NGKs for the 2005 300x model... I will double check the color of the plug wires but I know my 2005 has gray. His is a 2005 but will double check.

Whats the deal with the grey wires? Good or Bad?

[Stitch King]

Been running champions. Was told by many that there is no correct cross over to NGKs for the 2005 300x model...

There is not a direct crossover because of the Stainless Base used in the Champions. The NGK's use zinc plated steel. Otherwise the BR8HS is a direct crossover. For $12.00 a set, it's worth a try. If he wants to spend big bucks he can use the Iridium's BR8HIX and drop $50+.

Years ago when I was a Drivability Tech at a VW and Mazda Dealer, Champions were the first thing I'd look for. More often than not they were the source of the problem.

Regarding the "Grey Wire Issue", I understand that was related to the CDM's on the old style Ignitions with the Stator and not sure it applies to the Direct Fire Coils the 300X uses. Might be wrong on this one...

Was the boat taken for a run with the DDT or was it checked on the trailer only? Might show something different when under a load. Check TPS voltage throughout the range on the DDT only. If it aint right you wont get the timing that motor needs to run or the fuel it wants either.

Ken

[Stitch King]

Had the second cup of coffee now fully awake.

The TPS is a long shot.....Really sounds like it's starving for fuel. Just thought of some more stuff to check.

Restrictions in the fuel system....Run it off an outboard can and see if it does any better. That will tell you if the system has a problem with Anti-siphon valve, Primer Bulb, kinked hose, fitting restrictions, plugged fueltank pickup screen. Once had a spider build a nest in the fuel tank vent on the deck. Melted down a BBC due to fuel starvation. Drove me crazy until I found it.

Is the fuel line pressure at the rail 39 PSI when under acceleration in the water? At idle on the trailer it's easy to fool you into thinking everythings ok. Also check the fuel pressure to the Vapor Seperator. Should be 6-8 psi.

How bout the Water Separating Filter? Is it new? I don't think there's a filter to plug up that is inside of that Vapor seperator but will look in the manual later.

[Stitch King]

One more thing...and it's a longshot.

Anyone fiddle with the ignition key lately? I remember reading somewhere that you can acutally get these motors back to a break in mode by cycling the key in a certain sequence. Not sure if the DDT can see if it's in the Break in Mode or not.

[jerry]

put a smaller prop on and see if it will go to 7000rpm

[fastcat300]

possibly it could of sucked something into the intake,open the butterfly and check down inside, possibly stuck in the reeds now.and if its the boats im thinking of some of them were really heavy and would just never run.

[Hydrilla Houndawg]

possibly it could of sucked something into the intake,open the butterfly and check down inside, possibly stuck in the reeds now.and if its the boats im thinking of some of them were really heavy and would just never run.


It may be the boat your thinking of White with blue carpet? I am not sure what its gunna top out at but so far I have found him 4mph in set-up alone. It still needs a little tinkering with. Just for the heck of it I had him pull the cowl off and check to see how far open the butterfly was at full throttle. Its a full 1/4" less then what mine opens to. It could be as simple as a linkage adjustment. I sure hope so. Not sure what the boat weighs but it sure feels heavier and acts like it. One down fall to those boats I have found is not a single one was ever built the same.

[gutterball1]

Hi, Im very interested in what you learn here, I have a 22 ft cougar mtr with a 2001 300x on it, trying to spin a 25 pitch trophy, and it is doing virtually the same things, wont spin past 6000, ddt shows its fine, will not spin a smaller prop up much better. plugs are fine, a friend with the same setup says his would spin 6800 all day at 90 mph. This boat will do 75 maybe with two guys and low on fuel.
Thanks

[hydroo]

Try a new alternator.
Make sure the pins that connect the coils to the coils harness are making contact. Also the connection of the coil harness to the motor.

[Stitch King]

Rich,

Did you get this figured out?

Ken

[Hydrilla Houndawg]

Rich,

Did you get this figured out?

Ken

Not yet Ken. The guy went out of town and we are going to trouble shoot on Tuesday or Wed of next week. I will be sure to post results though.

[Dave S]

I have seen it before.....tryed to get a boat go fast and fail.:o Just did a set up on crackmate..... motor will not go past 6200 not my bad. I did not do motor. It happens. V8 OMC not my motor on velocity 70 mph.... is that all????? WTF. It happens. Some are just dogs trying to BARK.;) Keep trying.

[hydrostream1]

The DDT is only going to show what it has inputs for,crap in crap out,so The other parts like fuel pressure,high voltage out on the cdm`s,crank sensor will not show on the DDT.Optis are another that require more diagnosis on a running problem,air pressure,fuel and other that the ECM does not have an input for.On your RPM problem I would send the injectors out to brucato and let them clean and flow them,they can also recalibrate them as well if out of spec.

[whipper]

Im thinking like Hydrostream1 injectors or hows the plugs look? Have you done a wot then shut down and check for to rich? I know my promax can loose that much when rich. I set it up better now and picked up 3mph with a 25. If you have a ecu you can try try that also. Swap ECUs and see if yours looses 10mph?

[skydog]

injectors