New 225 ProXS Questions

[MIZ-ZOU]

2 week old '08 225 ProXS with approximately 7-8 hours on it. The motor idles fine, but misses when you give it gas. Once above 1200 rpm, it runs fine. It ran perfectly the first 2 times out, but has died several times in the last few trips. Is this something that is related to the double oiling, or is something else going on? I have tried pumping up the primer bulb again before taking off and it doesn't seem to change anything. Also, when starting the motor, the starter sounds a little sluggish. The battery is rated at 1080 CA/800 CCA and is new, but could this be part of the problem? This isn't really what I expected from a new motor.

Also, what "sound" do these motors make? I'm used to the EFI sound. This motor makes a sound that would be hard to describe. Sort of like a consistent "whirp-whirp-whirp" at idle....I know, that sounds dumb. You don't hear it when you give it some gas. It almost sounds like if you had a vacuum leak in a vehicle. I've been in my buddies boat with an '05 200 Opti on it and I don't remember that sound.

The motor runs well at top end, but I'm still only getting 5600 rpm and 70.6 gps at WOT. The boat is a Triton 200X2 hull with a 25 Tempest and a 10" plate. Shouldn't I be propped to get 5800 rpm or so? Others that I have spoken to are getting 73-74 light at 5800 with the same setup. Maybe the motor will loosen up?

Sorry for the long post, I just want to make sure that there's nothing to worry about with this motor. My dealer is 2 hours away, or I'd just run down there and have him check it out...




Modified by Tr200Seth at 9:43 AM 8/24/2008

[jbh3]

I'm sure one of the Merc techs will be along to address this. In the meantime I'll relate my experience. You need a battery rated @ 1000 MCA - minimum. Make sure the battery is getting and holding a full charge. Don't depend on the engine to fully charge it unless you do a LOT of running. If your built in charger doesn't have a bank for the cranking battery, consider upgrading. Yes, the XS engines have a different sound than the "regular" Opti engines. I ran a 225 Opti for 5 years and noticed it the first time I ran my XS. The hesitation you describe may be due to dirty plugs from the double oiling. I believe some have remedied similar situations by running 89 octane and/or cleaning and regapping thier plugs to .40(?). Run the decarb agent of your choice (Quickleen, Seafoam, etc) in EVERY tank. You may very well see a few more RPM's as you put more hours on the engine. May also consider raising engine height at that time. FWIW, mine is a 2007 225 Pro XS on a 20XHP and will turn a 26 Tempest around 5900. Sounds like a nice rig. Good luck!

[EuropeanAM]

Agreed. Battery voltage and capacity is VERY critical on these engines.

If you've not been running quickleen, you should start now (and also may need to replace or clean the spark plugs). 89 Octane fuel does seem to improve idle quality in many cases, as does regapping the spark plugs to .040".

What are you holding for water pressure at WOT? We're looking for a "minimum 15 psi". If you're much above that, it may be possible to raise the engine slightly to bring RPM's up.

Let us know if we an help any more.

[MIZ-ZOU]

Yes, I run Quickleen. I played around with the plate a little. Here are the results:

originally 5" Below Pad, 5400+ rpm, 30 psi, 69.8 gps (the dealer told me that where it was at was the optimum setting for this boat)

raised to 3.5" BP, 5600+ rpm, 26 psi, 70.2 gps

lowered back to 4" BP, 5600+ rpm, 26 psi, 70.4 gps

I figure that the difference in the last 2 numbers could be attributed to the temperature and wind as much as the JP setting. All numbers are with a light load. With 2 people and a tournament load, I only lose about 1 to 1.5 mph. I'm lost...I don't know whether to go up or down. I've never heard of anyone with my hull running above 3.5" BP. Most are in the 4" to 4.5" range.

I will post this in the Triton forum also and see if anyone over there has any ideas either. Thanks...

[EuropeanAM]

Looking at those numbers, you could TRY 3" and see what happens. You've got adequate water pressure, for sure. Just watch your water pressure!

Key here is to keep going "up" until you reach your maximum speed "sweet spot" but still retain a decent hole shot. If you get too high, you'll note the speed falling off.

These adjustments are best made "same day, same conditions" so that you can compare "apples to apples", so to speak.

Not a bad idea to talk with other owner's, but take their experiences with a grain of salt... each boat/engine combination CAN be different!

[Dr. No]

I have a 210 X2 that runs best at 3 3/4" below the pad. It was chinewalking bad with the 25 tempest and I went to 25 trophy and it runs and controls good now at 73 gps and turns 5900 RPM. This is with 250 pro xs.

[blackmax]

Some of these engines stumble at off idle more than others,due to the fuel mapping in the ECM,the sound you hear sounds like the air compressor pumping,RPMs could stand to come up alittle,I hope you broke this engine in by the book,10 hours of brake in before hammering on it for any length of time.

[MIZ-ZOU]

It was broken in by the book...1 hour of 4000 to 5400 rpms (or 3/4 throttle), then 3 hours of varying the throttle every 2 minutes or so. That's what the book says on the ProXS.

[dathom]

I have the same issue with the off idle miss. It has done it every time I have had it in the water. It has 10 hours on it now. Took it to the shop and no errors were detected. The dealer is researching now. There is a couple other threads on this site with the same issue... If you find out something let me know and I will do the same....

[EuropeanAM]

With the "off idle miss" there is "specific protocol" that must be followed. Have your tech contact Merc directly for info on how to address.

There is not "one solution" to every issue.