Plugs RE-GAPPED TO 44- 2008 225 proxs

[billproxs]

Thanks Don for all your yrs., of advise. I have re- gapped my new plugs to 44 and Motor now does seem to idle better again when pulling off trailer and now doesnt die on me after backing off trailer,or after idling for a few min's while putting in gear,which is needed at a ramp with wind blowing and busy boats everywhere. But I will say that now it's back to the sluggish Hole shot at ( 44 ). Better hole shot at ( 32 ).
Don can you tell me why I would have needed Mercury to do a PCM reflash back in 2008 if the idle problem could have been solved by re-gapping plugs to 44 ? Just wondering cause if that fixed it (PCM REFLASH ) ,then why the 44 gap. The 32 Gap did give me more hole shot power . Be nice to have both,idle /hole shot,but glad to have good idle back.
Thanks Don as usual.

[lpugh]

As simple as it seems spark plug gaps are a very complicated issue with many things to consider, such as air fuel ratio, compression, volumetric efficiency, ignition output and the dielectric strength of the secondary ignition system. Unless you have some type of ignition problem the .044 plug gaps will not cause a slower hole shot.

Wider plug gaps will light off the fuel mixture more reliably than close gaps butt they will put more stress on all the secondary ignition parts just like a worn plug will.

The additional plug gap will require the coils to build more voltage than the .032 gaps. There is a possibility that a coil is weak or there is secondary leakage with the increased voltage demand. That would account for the slower holeshot.

All that being said I prefer wide gap plugs for all the benefits in idle quality that they have. Wide gaps are also more resistant to fouling.

POINTS TO PONDER:
The air we run through a motor is insulator

With a 10 to 1 compression ratio, all the insulating ability of a 1/2 in of air space is compressed in to .050

If a coil has just enough energy to bridge a 1/2 in air gap at sea level it will only bridge a .050 gap when compressed at 10 to 1

The hydrocarbons in fuel are a electrical conductor! That is why a rich fuel mix requires less voltage to fire the plug.

A coil will only build as much voltage as required to overcome the resistance in the circuit. The coil may be capable of 50,000 volts, if it only needs 20 to overcome the resistance that is all that it will make.

Wider gaps force the coils to build more voltage before the spark, resulting a stronger spark. The wider gaps also expose more fuel mixture to the spark.

Thinking this thru you can see how all the variables above will effect plug gaps.

[EuropeanAM]

Good information, Leon.

In addition (and more importantly): Aside from variables in air temps, humidity, barometric pressure, ELEVATION, etc- we ALSO have to deal with the MUCH wider variable (today) of FUEL QUALITY.

These engines are being expected to run well on fuels that (despite pump advertisements) often contain BUTANE ratings that are LOWER than the equivalent of 87 octane. Such fuels are hard to burn at ANY plug gap.

Ethanol content is one of the biggest contibutors to this problem. If you have continued concerns/difficulties, you might consider switching to a different (high traffic, well known) fuel BRAND, and perhaps MID GRADE (89 octane). Fuel octane tends to degrade as the fuel sits/ages.... if you end up buying fuel that barely meets the minimum (87 octane) spec, and it degrades even slightly: Performance problems occur.

Adding to the above stated problems with Ethanol is that Ethanol is INFINITELY soluable in WATER. This means that it is CONSTANTLY attracting atmospheric moisture into your fuel. Water has essentially a ZERO octane rating... and essentially a ZERO butane rating. Averaging even a SMALL percentage of "zero octane" content into your overall fuel tank contents can EASILY reduce your overall fuel octane by SEVERAL (or more) OCTANE POINTS.

I would NOT recommend purchasing fuels above 89 octane for your specific engine, Bill- as substantially higher octane fuels can add a whole new "wrinkle" to the equation.

[billproxs]

Thanks for all the info. But if the PCM controlls all the electric/timing/fuel/air mixer at higher perssure with a gap of 32, and the hole shot should be better using carbon-fiber reed valves when slaming on the throttle ,then it seems that the Mercury folks through testing gained the extra 300 rmps they were after over the standard Opti.,using 87 fuel.I have seen 10% E-fuel around for yrs now.Just seems that the 225/250 proxs would have great hole shot and great idle with this design. Just thinkin out load...nothing more. I understand the 87-89 fuel problem your stating/kind a like the 89 is the old 87 with the E-10% added. I had the Motor put on a print out and it all read ok.This Motor runs really good in all other situations.All im saying is with a 32 plug gap this Triton 20x2 will come up out of the hole like a Apache Chopper ...lol. But with a 44 gap its a real slow dog getting up. but it runs good and i like the better idle,so will keep it there. Thanks again Don for your answers.Sorry to run on,i guess im picky. lol.

From Top...
The 225 Pro XS shares the same good looks as its 225 OptiMax cousin: black-on-black-on-black finish, rakish cowl styling and an overall sharp appearance. However, the real enthusiast quickly picks up on the sporty Mercury Racing decals and secondary air-intake vent on the rear of the upper cowling.

Obviously, the decals are for eye appeal, but the extra air-intake passage is a fine example of form following function.

One way to create more horsepower in an internal-combustion, spark-ignition engine is to increase both the fuel flow and the air flow. A common analogy is that an engine is simply a pump: air goes in through the intake and out via the exhaust.

The additional air-intake passage on the OptiMax 225 Pro XS cowling enables a substantially larger volume of fresh air to flow to the intake, allowing the engine to breathe easily at any rpm.

The midsection, including the power-trim system, transom-bracket assembly and the exhaust housing, are identical on both a stock 225 OptiMax and the OptiMax 225 Pro XS.

... To Bottom
Moving on down to the lower unit, the OptiMax 225 Pro XS comes standard with Mercury Racing's Torque Master gearcase, painted black to match the rest of the outboard. The Torque Master is designed for extreme use, that is, for speeds of up to 80 mph.

Sharing the same gearcase housing as a standard 3.0L, there are four water pickups at the tip of the nose: two on top and two beneath. In addition, the Torque Master retains eight water-intake passages on either side to ensure that plenty of cooling water gets to the powerhead.

On the inside is where the Torque Master is really tough. The propshaft is larger than a standard 3.0L propshaft. In fact, it's fifty percent bigger, making it capable of withstanding semisurfacing mounting heights and able to hold up under the brutal loads inflicted if you go wave jumping.

Yet, if your boat is an ultra-fast design, such as a Bullet or Allison, here's some good news: Just before we went to press with this issue, Mercury told us that the new 225 Pro XS will be available with its famous Sport Master gearcase — complete with solid mounts — as an option. In fact, this is the combination Mercury will be entering in BWB's upcoming 3-liter 225 shoot-out. The Sport Master is designed to run at speeds well in excess of 100 mph. It features an elongated bullet nose-cose with low-water pickups, a crescent leading-edge upper strut and a factory torque tab on the skeg.

Under the Hood
We unlatched the cowl and set it aside to get a good look at the the heart and soul of the 225 Pro XS: the powerhead. Externally, the 225 Pro XS powerhead is pretty much identical to a standard 3.0L OptiMax. Let's take a quick look.

Starting on the port side, you'll find the pulse fuel pump and the vapor separator tank (VST). The VST contains a high-pressure fuel pump and a canister-style fuel filter. Fuel flows from the boat’s fuel tank to the pulse fuel pump and on to the VST, where the high-pressure fuel pump sends fuel to the fuel rails and fuel injectors. Fuel volume exceeds the demands of the injectors, so excess fuel returns back to the VST. The constantly moving fuel tends to stay cooler, thus preventing pockets of vaporized fuel in the system and the aggravating "vapor lock" conditions we used to experience with engines on hot summer days.

The fuel and oil lines, wiring harnesses and control cables enter the lower cowling on the forward side of the 225 Pro XS. The throttle butterfly plate is situated on top of the cast aluminum air-intake plenum at the front of the engine.

The starboard side is home to the electric starter and various other electrical hardware, including the battery cable connections, fuses and Propulsion Control Module (PCM).

Now, step behind the engine to find the cylinder heads and fuel injectors, and the idle relief boot.

Looking down on top of the powerhead, you can easily see the flywheel, the belt-driven 60-amp alternator and the air compressor for the fuel-
injection system.

So far, so good, right? But what makes the OptiMax 225 Pro XS faster?

Software and Hardware
Like other Mercury DFI outboards, the PCM computer precisely controls the ignition and the direct-fuel-injection systems. However, the PCM on the OptiMax 225 Pro XS is programmed to squeeze every bit of horsepower out of the engine by manipulating the timing and fuel flow for maximum performance.

For instance, a production 225 OptiMax runs 80-psi fuel pressure in the fuel rails. Like the 2.5XS and 250XS, the 225 Pro XS fuel system is pumped up to 95 psi to get more fuel into the combustion chamber and to enhance the atomization of the fuel mixture. Mercury engineers tell us that this allows the engine to run more rpm and a bit cleaner due to the better penetration of the fuel into the combustion plume.

The cylinder heads on the 225 Pro XS are very similar to those found on Mercury Racing’s 250 XS, and feature a distinctively different combustion chamber shape than you’d see on a production OptiMax. The compression ratio’s a bit higher, too — 5.8:1 for the 225 Pro XS versus about 5.3:1 on a standard 3.0L OptiMax.

What about spark plugs? The 225 Pro XS uses plugs with a little longer reach to place the fire exactly at the sweet spot of the fuel spray.

Are you keeping track of all this? Good, because all of these seemingly minor differences make the 225 Pro XS a major powerhouse.

Let’s keep moving. We’ve talked about the cylinder heads, so it’s time to talk about pistons. Both the 225 Pro XS and the standard 225 OptiMax engines have a strange-looking, moon crater-shaped dish on top of the pistons. Why? Mercury says that this area helps concentrate the burning fuel plume where it’s most effective.

Here’s another important performance item: Standard 3.0L OptiMax pistons are rather flat on top, but the 225 Pro XS pistons are domed, to perfectly match the specially engineered combustion chamber shape.

Reed On
At the front of an OptiMax two-stroke engine, behind the intake plenum, there’s a one-way valving device commonly called the reed block. The reed block has several small, flat plates (called reeds) that allow air to enter the crankcase, but prevents the air from flowing back out.

When the throttle is opened, air rushes into the reed block and the individual reeds bend a little to let the air pass. Close the throttle, and the reeds snap shut to keep the air where it belongs.

Many large outboards, including the standard 3.0L OptiMax, use steel reeds in the reed block. Steel reeds are relatively inexpensive, durable and work great for most applications.

Serious boat racers have been using variations of fiberglass or, more recently, carbon-fiber reeds for years, because when you slam the throttle open, fiber reeds flex open more quickly than steel reeds.

Early on, the fiberglass reeds performed well, but had a limited service life. Not so with the carbon-fiber materials that have surfaced in the performance-outboard marketplace. These newer composites reportedly last nearly as long as comparable steel reeds. To prolong the life of the carbon-fiber reeds, the reed block in the 225 Pro XS is rubber coated, cushioning the reeds each time they close.

You’ve probably guessed by now that the 225 Pro XS, like hardcore Mercury Racing outboards, is equipped with carbon-fiber reeds for snappier acceleration and better throttle response throughout the entire rpm range. Technology prevails.




Modified by billproxs at 7:46 PM 5/12/2011

[EuropeanAM]

Interesting read.... pretty accurate on the external observations (with a miss of some obvious differences, such as the COLOR of the direct injectors).

One terribly mis-stated section is the FUEL PRESSURE. Standard V-6 Opti's operate at an 80/90 Air/Fuel pressure.

High Performance models (225/250/300, such as the ProXS or XS Versions) operate at a 95/110 AIR/Fuel pressure setup.

They also utilize a "multi-strike" iginition coil, which is very different from their "standard production" cousins.

Aside from all this.... I can tell you from MANY experiences that FUEL QUALITY does, and WILL make a substantial difference in engine performance. It's ONE of a few items that the manufacturer has NO CONTROL over once the engine leaves the plant (and you have to take the "word" of the information at the PUMP when you buy it).

Every year we have DOZENS of customers come through our shop with a WIDE ARRAY of performance complaints, that are solved by simply CHANGING FUELS.

[lpugh]

I have to agree with what Don is saying about the effect of fuels in the equation and say again the .044 plugs gaps are not the real cause of your slow hole shot.

The wider the plug gap, the better the odds are of initiating combustion every event as long as the spark bridges the plug gap.

When you open the throttle the cylinder pressure goes up dramatically (more electrical resistance across the plug gap) . Under that condition a 32 gap may require 20 KV to fire, where a 44 gap may require 25kv to fire. If a coil is weak and only providing 24 kv the motor would idle well but drop that cylinder under heavy load, As the rpm comes up to max. the motors volumetric efficiency falls off a little, requiring a little less voltage and it begins firing again.