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Big improvement after Ringfree and spark plug change, twin 225's. Stamas 288 Liberty.

B

btravlin2

Regular Contributor
As some of you may know, I've been slowly bringing these used '04 motors I bought up to spec. I've chased some confusing issues along the way that confounded me, but I nearly have them running correctly now.

I have only run 7gals of the 40:1 RF shock treatment. I had intended to run 12gals, and still may. However, while running the treatment last week under way, I noticed the port motor was vibrating under load and not having a lot of power. A mechanic friend, who is good on Hondas, suggested changing the plugs for a start, since I didn't know the age of them. Bingo!! One plug was black and carboned up. The others were a nice, dry tan.

I went for a spin, and for the first time since I've had the boat, she ran close to how she should. But not quite.

I was able to hit 6200rpm on the stb motor, but only 5900rpms on port. This was with motors trimmed as high as possible without cavitating and no trim tabs. However, my max speed was only 41mph. I know of 3 other exact same boats with various brand 225's that max out at 45-47mph.

So my question is.....why only 5900 on port? Finish the RF shock treatment, maybe?

I've already checked the throttle cables (new) and I know the intake throat is opening completely. So other than removing more carbon, I don't know what's holding the port motor back. Could it be that this motor has lower compression? I won't know until we do the compression next week, but I want to finish the shock treatment first.

Last of all, I'll have the props checked. They might not be perfectly matched. The local guys, Baumann Propellers, are really good.

Any ideas on the WOT rpm discrepancy and the low mph?
 
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If one prop is right hand rotation and the other is left hand rotation, you will have to run in reverse to go forward. The lower unit is not made to do that.

First thing to check would be the throttle cable adjustments. Chawkman has posted that procedure somewhere on this forum. Without getting into the adjustment....with the top covers removed, look at the lever on the throttle bodies and compare the roller location inside the lever. Both should be near the end of travel (indicating that the throttle body is fully open) and should be the same. If they are the same, then the cable adjustment is probably pretty well right on.

Mike

Mike
 
Thanks Mike.....yes, I've already checked that, but will check again. And thanks for reminding me that these are counter-rotating props and can't be switched.
 
You can check throttle position sensors by unplugging them and doing a "sweep" test with the engines not running . Meaning you can hook up an ohmmeter to the reference and ground termials and then slowly open and close the throttle (sweep). This way you can compare the port engine TPS to the stbd. They should pretty much mirror each other. If the port shows higher resistance than the stbd sensor, then the sensor is bad or out of adjustment. Or, there IS a problem with the throttle linkage or cable.

NOTE: Most sensors today don't have adjustment. Most bolt on to the throttle body in a preset/precalibrated position. I don't know your outboard so you will need to determine if any adjustment is available on your rig.

A more accurate TPS check is to backprobe the TPS terminals with a voltmeter with the ignition in RUN and perform a sweep. This will indicate what voltage the sensor is reporting to the ECM from idle (usually just under 1vdc) to WOT (usually around 4.5vdc)

Again, you're primarily interested in the port reporting very close to the same as the stbd.

Either of these tests are good to know how to do, especially the live voltage version. Spikes or dropouts in the display as you SLOWLY sweep the throttle can point to worn areas inside the sensor that can rob performance and cause running issues.

Just another idea about what might cause this symptom.

Good luck.
 
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Good to hear that you have those babies up and sunning.

Very good advice all around from Mike and Jimmy. If you need the procedure for adjusting the throttle linkage it is back toward the end of Chapter 3 of the Helm Shop Manual. I just checked mine a couple of weeks ago. If you don't have that, send an e-mail to me at [email protected].

What cylinder did the sooth-coated plug come out of. If #6, you might want to check compression and possibly use some concentrated Ring Free or Sea Foam sprayed in there to get carbon off the rings and valves. I've forgotten all that you have done to those motors, so you may have already done all of that.
 
The plug was port side, middle (#2?).

I didn't know a sensor was involved with throttle. I'll take a look. Could a bad O2 sensor cause the 300 rpm difference on that one motor? The manual explains how to test them so l'll do that too.
 
Yes, O2 sensors are part of the fuel "mapping" strategy for the ECM and a "lazy" one could cause power loss by causing an imbalance in fuel delivery. A poorly functioning O2 can drive the fuel to air ratio either rich or lean and the further the ratio drifts from the designed "target" of 14.7 to 1 when the engine is at operating temperature, then performance can definitely be affected.

Since you say you were unaware of the throttle sensor I will tell you that the ECM looks at several INPUTS in order to pulse the injectors at the proper rate to deliver fuel for maximum performance with lowest emissions.

The ECM looks at:
Inlet air temperature
Engine coolant temperature
Barometric pressure in the intake housing
Throttle position
Exhaust oxygen content
Engine rpm.

Later model engines look at even more data like real time fuel pressure and actual fuel ratio of exhaust gases.

Each input is associated with a sensor. For example, your engines will have what is called a MAP or manifold absolute pressure sensor. That sensor is the "load" sensor for your engines.
If the MAP report is skewed and misrepresenting manifold pressure, then performance will suffer. The same goes for any one of the sensors I listed as well as if your EXPECTED fuel pressure is low.

I say EXPECTED because I don't think your engines use live fuel pressure sensors. Your ECM simply EXPECTS the fuel pressure to ALWAYS be at a given value. Therefore, should the fuel pressure be lower or higher than designed the ECM has no way of "knowing" and can't compensate for the difference. That's why cleaning and maintaining the VST and filters is so important.

I hope I haven't confused the issue with all of this but I see a need for you to understand what COULD be involved in sorting out a "low power" condition.
 
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jgmo......good info. I will check throttle linkage, O2 sensor, and then go on down the line until I find it. But first I think I'll finish the RingFree decarb to eliminate that possibility. Thanks....
 
Yes, that's what I would do too, keep up with the decarb treatment.

The rule is: Do the easy stuff first.
Good luck.
 
I'm going to finish the decarb this week. Will it make a difference whether I do it in neutral at the dock (3000rpm), or under load on plane (4200rpm)?
 
Just for reference........it's a good thing I changed the oil after the RF decarb. It was very dark. I imagine it takes quite a bit of carbon to do that to 8 qts of brand new Mobil 1.
 
That's a good testimonial on why it's important to run Ring Free (or some other quality decarbonizer) in regular dosages through you fuel system once or twice a year. I do a lot of trolling in the spring and fall right near my home, so my 225 doesn't get run out a lot during those times. After the spring rock fish season and after the fall season, the fuel is doctored with a bottle of Ring Free. An alternative is to use fuel laced with Valvtect, which is available at some marinas throughout the US. Valvetect is also a fuel stabilizer, so you can kill two birds with one stone, so to speak.
 
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