WOT speed on a '83 20' SF w/200

[ThePHNX]

OOps forgot no cams. You get the idea though.
What do modern 2-strokes have for mechanical timing? Are they still just ports and reed valves or what? Trying to remember what my Mach One was like for engineering, know that it never wanted to run less than 6 grand!-(
BTW, the locals have told me they don't trust the oil injection systems (have one on "Plunker's" Mariner): they advocate tossing it and mixing the fuel. Am gonna stick with the oil injection for now but wonder if there's any way to quickly sense no oil flow when it happens?
HBH

[spareparts]

my book shows the WMV 3 carbs as the XR6( 150 hp) and the WMV5 as the 200,
WMV3 XR6 jets
Main .074
Idle air cylinder 12346 .044
cylinder 5 .048
Vent air .082

WMV5 200
main jet cyl 1,2 .082
cyl 3456 .080
idle jet cyl 1,2 .052
cyl 346 .028
vent jet .096

it gets pretty confusing when you start changing around carbs and jets, see if you can find a complete set of 200 carbs, confirm the jet sizes and put them on

timing
pick up 2-9
total on XR6 19 @ wot 19
total on 200 carb @wot 20
total on promax without spark advance box 25

not much difference between the motors with the spark advance box, but with out on the promax 25, keep in mind the jet sizes, they are rolling a lot more fuel in on that one, and on the XRI, the injection goes rich at wot throttle position. Don't push it unless you're getting fuel to it. As far as the oil injection goes, unless a new crank gear was installed, don't chance it, especially if you decide to twist it up.
Go back to the hull running wet, try a jackplate, and if you are getting a good enough hole shot, start tappering the hook out of the hull, use a straight edge and DA.

[Bigshrimpin]

Spareparts - I've read that the best carbs for a merc 2.4 or 2.5L motor were the old wh-20's or wh-22's . . . I can't figure out why there were so many different variations of carbs for these motors.

What about the exhaust tuner on the XR6? I believe that is different that a 200hp 2.5L tuner?

[spareparts]

i can't figure the carb thing out either, i just try to stick with what the book says, keep it on the safe side, jet up but not down, you'd have to spend a lot of time on the dyno, blowing up a lot of motors to figure it all out. the biggest difference in the carbs is the size of the venturi, lots of them had the same throttle blade size, but the venturi was necked down to pull the power back for lower hp rated engines. As far as the tuner goes, we used to cut 3" off the stock one, pull the can and drill 6,1/2 holes in the bottom of the housing, don't know if it helped, but it sure sound faster( satisfied most of the bassholes). The best deal on a tuner is to use the promax tuner, its far cheaper than the aftermarket, flows good, and makes power, if you are running the big front half, the promax reeds are another hidden bargain( haven't checked prices on these in a while, used to be the best deal).

[Blue_Heron]

Spareparts,
The carb thing is a little confusing, I agree. The jets you list for the WMV3s are what they had when I got 'em. I jetted up on the mains and vent jets, but not quite what you list. I have:

Mains
Cyl 1,4 - .080
Cyl 2,3 - .082
Cyl 5 - .084
Cyl 6 - .078

This is what the manual calls out for a WMV 18 which would be on a '99 or '00 model year 200. That's the manual I have. The WMV3s have the large bore venturis, so it should be getting plenty of air.

What I would like to do is find a set of WMH3s. If I've got my numbers right, those are the 200 hp carbs that came out in the early 90s with the accelerator pumps on them. I've got the WMH6s with accelerator pumps on my XR4 and I like 'em.

Bigshrimpin,
I believe the WH carbs were used around the time Merc was running the 2.0 powerheads. Around the time they went to the 2.4 powerheads is when they went to the WMH series. Then sometime after they went to the 2.5, they brought out the WMV series. I agree that most Merc motorheads like the older carbs, either the WHs or WMHs.

Hey, didn't you have a set of carbs on ebay a while back?

[Bigshrimpin]

I had a set of wh-11's on ebay off a 1979 v200. The wh-15's and wh-20's came with the 2.4L v225. I'm running a molested 1981 2.4L v225 with wh-22's.

I still have that set of wh-11's and a second set of wh-22's for my other motor

T-Rex (spidey's cousin on screamandfly.com) jabbers on about the different carbs . . . I'm just learning this stuff myself from everyone else. The blackmax's are nice to work on and I've gotten lucky a few times getting parts for cheap. I'd love to have a new Suzuki 175, but I can't justify the expense with good running motor and the ammount I use my boat.

[spareparts]

the specs i wrote came right out of the Mercury manual for 99. i have never swaped carbs around other than swapping complete sets, like i said, it would take a dyno and a lot of time and money to figure it all out, looks like the guys at scream and fly have spent the time and money( cool site).

I keep coming up with more ideas as the day goes on, does your boat have trim tabs? If so are they mounted flush with the bottom. Years ago I had a customer with a 60 mph boat that wanted tabs put on it, i installed the tabs per the instructions, mounted flush with the botom, with the trailing edge 1" up in the full retracted position, he lost 6 mph. Not the first time someone spent money and slowed down. I had to repair the holes for the tabs and cylinders, move everything up 3/4 inch, remount it. He picked his 6 mph back up, and got the chine walk under controll. The tabs mounted flush efective increased the wetted surface, without a clean break at the transom, it actually sucked the back of the boat down( you would think it would lift the bow).

[Blue_Heron]

Bigshrimpin,
Yeah, most of what I know about Merc carbs, I got off of Scream & Fly. S&F was also where I found out about the timing module (idle stabilizer)on some models acting as a rev limiter. I disconnected it on my XR4 and it jumped from 5600 WOT to 6200. I repropped it and got it back down to 5800. Picked up about 6 mph top end and still have good hole shot. It's a great forum, but like any , it's sometimes hard to tell who knows what they're talking about and who doesn't.

I'm with you on the boat budget. With two boats, there's only so much the Mrs. will tolerate. I just threw five bills at the trailer under the Action Craft yesterday; new tires, hubs, axle, springs and associated hardware. Would have been at least seven if I hadn't done the work myself. B-O-A-T = break out another thousand.

Spareparts,
Yes, I do have trim tabs. They're mounted flush to the bottom and hard against the outer chine. I think the trailing edge is 5/8" above the plane of the hull bottom. I didn't think about them limiting bow lift, but that makes sense. My action craft had the opposite problem, too light in the bow, and I ended up putting transom wedges on her so I didn't have to drag the trim tabs in the water to keep her from porpoising at low speeds.

The reason I keep going back to timing is that just after I got the boat, I ran it with the 22p prop and got it up to 5500 and 49 mph. I wonder if the timing module had a hiccup and bumped the advance? Performance has dropped off since then. Maybe I just had it very lightly loaded at the time. Anyway, I'm gonna keep playing with it.

Thanks to both of you for your posts. Have a happy Thanksgiving. I'm loadin up the wife and kids and Goin' to visit the in-laws and see if I can put a bullet in ole Bambi.

[Bigshrimpin]

http://www.biggerhammer.net/mercury/

This was posted before a while back, but it's a useful reference.

This is another good site.
http://www.byuboyz.com/

The Cherry 2.4L project.
http://www.byuboyz.com/modules.php?n...warticle&id=45

Good Luck with everything!!

[Bigshrimpin]

"horsepower, it don't matter what color the engine is."
Shame on you Blue Heron; you obviously know better.
For one thing Horsepower ratings are as much marketing hype as engineering (and all indications are that Mercury is more of a sales organization than an engineering one)
Then there is this business of power curves where power and torque vary with engine design for any given RPM.
There are known occurrences of horsepower being overrated 20% or more by marketers so a spread of 40 HP DOWNWARD is certainly possible.
In which event would be inclined to trust Yamaha's (or just about anyone's) veracity over Mercury.
As you can tell, have gotten a pretty low opinion of Mercury Marine.

PHNX'Y - How many Yamahas do you count in this picture?


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