2002 XR6 Improvements

[dmackaravitz]

Serial # OT494213
2002 150 XR6

Received this motor last year and want to make some upgrades to it to get some better performance.
Been reading on here about some mods you can make that will slightly increase its output, but still had a few questions.

I read that removing the Idle stabilizer and setting WOT timing to 24 degrees is an easy way to see some gains, however for my model year the shop manual makes it seem as if my motor does not have this module, is that correct?

I plan to install Chris carson reeds, and while I've got it down to there, would it be worth it to get the heads cut? What kind of increase would I see from getting the heads done?

Some mention changing out the tuner, but would I suffer some low end power loss going that route?

And last mod was the hood scoop, Ive heard it mentioned, but cant seem to find the specifics.

Thanks for the advice

[EuropeanAM]

Idle Stabilizer is for earlier models- your engine has CDM ignition with an "ICM" (Ignition Control Module). Can't remove it or you have no spark at all.

Upgrading reeds from steel to fiber is a good choice. Several options here on the forums.

Heads could be cut- but I'd strongly recommend a CURRENT compression test before you even consider it. And since those engines are already not very forgiving on the fuel delivery system (especially in warmer weather), I'm not real fond of any big increase in compression.

Tuner: You "can" change the tuner, but you'll often suffer on the low-end/holeshot.

Just my opinions, of course.

[dmackaravitz]

Do you have information on hood scoop mod? I looked up your post for the 3L but none of the pictures would show up so it was a bit confusing.

[JOE54]

main jetsssssssssssssssssssssssssssssssssssssssssssssss sssssss be careful though, what boat is it on

[EuropeanAM]

Unfortunately some of the picture hosting sites have locked out pictures for "non-paying" accounts. No way for us to retrieve those.

[Merc2.4]

I'll prob be disagreed on this ,but it's just me and I like to modify motors, I'd put old school 16amp with switch boxes and coils etc ,cut heads ( u prolly got o ring heds), maybe a diff set carbs from wh series , 2.4 200 tuner , all this can b done in a days time for the experienced mechanic, but prob not for everybody , and of course u gotta rejet after all together , but if u have a pretty heavy boat ,prob better off to leave it alone. hope this helps

[John Jackson]

Very little loss on low end with a tuner. ON an outboard, the long small tuner is a restriction, and the tuner is more like a header collector on a 4 stroke.
On the hood scoop mods, the scoop on the top back of the cowl is removed, then reinstalled with screws a half inch longer, with half inch spacers to raise the scoop/air inlet. This allows more air in.

[ChrisCarsonMarine]

The cdm ignition system offers better holeshot performance than the switchbox system due to its timing curve,so I would stay with it.The motor does have O ring heads,we can cut them,but you will have to run premium fuel...ALL the time,better holeshot and midrange,no real top end difference.Shorter bell tuner will help mid through top end,hurts bottom end a little.Best bang for the buck in my opinion in importance order would be reeds,crankcase stuffers,tuner,heads...,Chris

[Merc2.4]

The cdm ignition system offers better holeshot performance than the switchbox system due to its timing curve,so I would stay with it.The motor does have O ring heads,we can cut them,but you will have to run premium fuel...ALL the time,better holeshot and midrange,no real top end difference.Shorter bell tuner will help mid through top end,hurts bottom end a little.Best bang for the buck in my opinion in importance order would be reeds,crankcase stuffers,tuner,heads...,Chris

Hey chris. I dont have much experience with the CDM, good to know bout hole shot , I think I had a guy tell me once that they changed back to switchbox and gain little rpm and such on top but I didnt ask bout while shot either. On and give me a call tomo to talk bout these parts I got. Thanks Robert

[OldTimer57]

The BEST mod, from experience, is to upgrade carbs. IE if you look in the parts catalog (at least for the '92 I had) the ONLY difference was the carbs. I replaced 'em with 175 carbs and it woke the motor up (when you look down the bore of the stock carbs, the venturi is VERY restricted. The 175 carbs less so. The 200 carbs even less so (but there were more differences in the older 200 blocks, different sleeves and such. Also, and I don't know if this affects your motor, but the sleeves on my '92 had notches cut in the top of the exhaust port which effectively lowered compression. I removed 'em and replaced them with sleeves without the notch and the low end / midrange felt MUCH stronger. Top end was improved, but the midrange was really perked up. This part is not an easy swap as you get to completely disassemble the motor and bake the top half of the block to remove the old sleeves. My wife was NOT impressed when she found this big black thing in her oven. Said "either you have burnt the hell out of a turkey or you are in big trouble..." :)

If you do the carbs and sleeves, you can get away with a shorter tuner (I used the 200hp one) as you have improved the lower end torque a lot and you can give up some in order to improve breathing on the top end.

Again, note, this was for a 92, the first year of the motor. Whether it applies to your motor, only Don or the parts catalog can say.

[OldTimer57]

Very little loss on low end with a tuner. ON an outboard, the long small tuner is a restriction, and the tuner is more like a header collector on a 4 stroke.
On the hood scoop mods, the scoop on the top back of the cowl is removed, then reinstalled with screws a half inch longer, with half inch spacers to raise the scoop/air inlet. This allows more air in.

Hate to disagree, but I had a 92 xr6. A friend (outboard mechanic by trade) also had one and we both went through the hop-up process. I was replacing the soft rubber motor mounts and removed the exhaust plate as well. Was astounded at the length of the tuner. Replaced it with a 200 tuner and the lower end of the torque curve went to crap. These are called "tuners" for a reason. At some RPM, the air column in them will tune to the harmonic frequency of the tuner and do a much better job of purging exhaust. But at higher RPMs that frequency will be too low and can even interfere with exhaust purging. There is a PERFECT length for a specific RPM (I used to race radio-controlled model airplanes, which used 2-stroke motors with what was called a "tuned pipe" exhaust system. We had to cut 'em 1/8" at a time and fly. At some point, the plane would gain speed. And each shortening would gain more until we reached "the" point. Trimming further tuned it to an RPM level the motor could not reach and performance would start to decline. The tuner in the outboard does the same thing. Tune it long and you get more bottom end but lose on top. Tune it short and you get more top end but lose on bottom. I think, for the XR6, mercury had to jump through a bunch of hoops to drop that 2.5L motor down to the 160-165 H.P. level to match marine requirements. Restrictive exhaust, restrictive carbs, reduced compression through that notched sleeve, and then the idle advance module that limited RPM. Remove all the nonsense and that motor would really run. If you go high-compression with smaller combustion chambers (Companies like Land and Sea used to sell machined heads with most any sized combustion chamber you wanted) you can really hit problems since buying gas on the road is an "iffy" deal. Stop at a mom and pop store where the truck operator snuck one over on 'em when he filled their underground tanks and you will see what a burned piston top looks like. I did that once and decided to forgo the high compression heads since I fished a lot everywhere.

YMMV of course.

[xcoach]

This thread has been a good read for an XR6 (2003) owner.

[leonreno]

If you like doing this stuff for fun then that sounds good but seems it would be easier and maybe cheaper to sell the 150 and buy a similar year 200. These motors aren’t that expensive now.

[Ranger Rod]

Relive the exhaust and you will feel faster.

[JOE54]

and sound faster toooo

[lpugh]

I have been this route a few times, aand would recommend that you just buy a EFI or even better a Optimax that has the desired Hp output you wish to achieve and replace the cowling lettering to what the boat is rated for. This is less risker and in the long run will probably cost less with better performance and fuel economy. Hopping up the motor is no different than simply installing a higher output motor.
There something to be said for plug and play, more time fishing and less time working on it

[JOE54]

+100 ^^^^^^^ and one bad tank of fuel can ruin it all

[dmackaravitz]

Thanks everyone for the input, boat is rated for a 175. I will most likely just go the route of Reeds/stuffers. Just got the prop worked by Ronnie Gilbert, and will be adding a 6 or 8" jackplate and that should give me some speed. Trying to be optimistic, would like to see 70mph with a 150. Have seen reports of this boat doing that, but not sure if they are honest numbers.

[lpugh]

Think about, generaly speaking for a bass boat it will take 10 HP for every MPH gained, 50HP to gain 5 MPH, Set up, Prop and weight reduction is by far teh best bang for the buck.
Another point I would like to make is that speed is like drugs, you get liitle and you just get used to it and want more of it, it is an endless cycle that gets very expensive

No matter what you do there will always be a faster gun out there

[JOE54]

+ 1 prop, set up ,lighten,( LITHIUM )my troll batt,36 v weigh 29 lbs, speed aint cheap, then work on mtr