Did Mercury Detune the 200 EFI in the Late 1990s? Pretty Good Evidence Here They Did.

[Bumblebeeman]

According to Bass & Walleye Boats magazine, it appears Mercury may have detuned the 200 EFI in 1997, 98 or 99. Bass & Walleye Boats had a 200 shootout (a competition among outboard engines) in the April 1996 issue with Merc, Yamaha and Evinrude running their 200's on identical Champion 191 bass boats. Mercury took top speed honors by 1.1 mph and had the fastest 0 - 30 mph and 30 - 50 mph acceleration times. On the dyno the Merc showed 206 hp, the Yamaha 204 hp and the Evinrude 199 hp.

The magazine had another 200 shootout in 1999 where the Merc 200 EFI had a poor showing. They tested 7 engines total, 2.5 liter carb and EFI Merc's and a 3.0 liter Opti, 2.6 liter carb and 3.1 liter EFI from Yamaha and 3.0 liter carb Johnson and 3.0 liter 200 Ficht Rude. The Merc 200 EFI top speed was just below middle of the pack, 2.4 mph slower than the Evinrude, and acceleration times were the worst of all the engines. Bass & Walleye Boats actually specifically said in the article the Merc 200 EFI was a big disappointment compared with 3 years earlier when it took top honors in all categories.

I ran in bass boat circles back then and the word going around was that Merc detuned the 200 EFI because they were just trying to pull too much out of just a 2.5 liter engine, smaller than OMC's or Yamaha's blocks, and there were reliability problems and to control warranty costs. There is a Scream & Fly post from February 2013 that says Merc detuned the 2.5 liter 200's in the late 90's to try to steer people to the Optimax, and to give customers the feeling that they were getting something for their extra money buying the Opti.

Does anyone know if Mercury changed something to lower the power output of the 200 EFI sometime in the late 1990's? In readers' experience running 200 EFI's or hearing from other boat owners, does anyone get the feeling that late 90's 200 EFI's develop less power than the earlier ones?

Thank you

[patchesII]

I know the 97-99 blocks were among the best 2.5 200's. I don't see a company doing that intentionally

[Bumblebeeman]

I know the 97-99 blocks were among the best 2.5 200's. I don't see a company doing that intentionally

For some reason the Merc 2.5 EFI performed poorly in the Bass & Walleye Boats 1999 200 hp outboard competition shootout.

[Motv18]

Different boats different runs, more likely merc supplied the latest prop to the efi and didn’t test, but spent days working the best prop on the opti.

[90 5.0]

For some reason the Merc 2.5 EFI performed poorly in the Bass & Walleye Boats 1999 200 hp outboard competition shootout.

It was probubaly what we call a “Monday motor”, with factory motors in everything from lawn mowers to ford 5.0’s there are “acceptable tolerances”.

For instance on a ford 5.0 the factory tolerance for deck height is +\- .005 in or out of the hole on the piston , plus a tolerance for head cc(I want to say it’s +\- 1cc. But my memory’s foggy on thatone. Factory heads are 64cc on the H.O. 5.0.

So what does that mean? On average they all run about the same, but you get one that’s got 65 or even 66cc heads, Pistons .005 in the hole and heads and intake with more casting flash in them etc it’s gonna be a bit slower. You get one the opposite direction and it’s gonna be just a bit faster with all the right stuff happening.

For super stock we had to run stock everything with nothing touched. So we would flow as many sets of stock heads as we had(always had a lot laying around working in a mustang shop in the 90’s), and intakes. Measure all the stock blocks we had and put together the best “stock “ packaged

I’ve seen 100% bone stock 5.0 gt’s run as slow as 15.@@@@ and as fast as 13.99, but the average was about 14.40/50(with me driveing them so no driver differences), my buddy Darrell ran a bone stock 92gt to 13.8@@ once, was fastest one we had ever seen. Only had timing bumped to 14deg and airbkx silencer removed.

Anyway, you get the point.

[eli]

Agree back in the day we had 3 Honda 70,s 1 was way faster than other 2. We had a 10 hp Johnson ran 25 on a 12 foot. Aluma craft neighbors had same year. 10 on a 14 foot aluma craft was faster by 2 mph. Cousins 9.8 merc beat us all

[tunnelmike]

Since they got 300+ hp out of the 2.5 platform and we turned those same consumer 200's over 3000 rpm's over their design limit I'm pretty sure it had nothing to do with pulling too much out of a 2.5. Just saying ......... Mike

[patchesII]

It was probubaly what we call a “Monday motor”, with factory motors in everything from lawn mowers to ford 5.0’s there are “acceptable tolerances”.

For instance on a ford 5.0 the factory tolerance for deck height is +\- .005 in or out of the hole on the piston , plus a tolerance for head cc(I want to say it’s +\- 1cc. But my memory’s foggy on thatone. Factory heads are 64cc on the H.O. 5.0.

So what does that mean? On average they all run about the same, but you get one that’s got 65 or even 66cc heads, Pistons .005 in the hole and heads and intake with more casting flash in them etc it’s gonna be a bit slower. You get one the opposite direction and it’s gonna be just a bit faster with all the right stuff happening.

For super stock we had to run stock everything with nothing touched. So we would flow as many sets of stock heads as we had(always had a lot laying around working in a mustang shop in the 90’s), and intakes. Measure all the stock blocks we had and put together the best “stock “ packaged

I’ve seen 100% bone stock 5.0 gt’s run as slow as 15.@@@@ and as fast as 13.99, but the average was about 14.40/50(with me driveing them so no driver differences), my buddy Darrell ran a bone stock 92gt to 13.8@@ once, was fastest one we had ever seen. Only had timing bumped to 14deg and airbkx silencer removed.

Anyway, you get the point.

Thats interesting. My brother had the quickest one I've ever seen. It was a 92 Notchback that would run low 13.90's. Your post tells me it was as rare as I thought for a stock 5.0 to run that quick. That was on regular street tires. No Drag radials

[tlwjkw]

jus "bench racin' bs" that got outta hand...... ever think tha "other brands" had made a slight improvement?.. these same folks that say yep, they did, have any idea as ta "how/what" they did???

[marks86]

It was probubaly what we call a “Monday motor”, with factory motors in everything from lawn mowers to ford 5.0’s there are “acceptable tolerances”.

For instance on a ford 5.0 the factory tolerance for deck height is +\- .005 in or out of the hole on the piston , plus a tolerance for head cc(I want to say it’s +\- 1cc. But my memory’s foggy on thatone. Factory heads are 64cc on the H.O. 5.0.

So what does that mean? On average they all run about the same, but you get one that’s got 65 or even 66cc heads, Pistons .005 in the hole and heads and intake with more casting flash in them etc it’s gonna be a bit slower. You get one the opposite direction and it’s gonna be just a bit faster with all the right stuff happening.

For super stock we had to run stock everything with nothing touched. So we would flow as many sets of stock heads as we had(always had a lot laying around working in a mustang shop in the 90’s), and intakes. Measure all the stock blocks we had and put together the best “stock “ packaged

I’ve seen 100% bone stock 5.0 gt’s run as slow as 15.@@@@ and as fast as 13.99, but the average was about 14.40/50(with me driveing them so no driver differences), my buddy Darrell ran a bone stock 92gt to 13.8@@ once, was fastest one we had ever seen. Only had timing bumped to 14deg and airbkx silencer removed.

Anyway, you get the point.

great post, I think a lot of that has to do with the model of the mustang as well, let’s use 92 for example. Take a 92 mustang GT loaded probably weighs close to 3400-3500 pounds, then take a 92 coupe base model, crank windows no back seats and your gonna save 500-600lbs

[90 5.0]

Thats interesting. My brother had the quickest one I've ever seen. It was a 92 Notchback that would run low 13.90's. Your post tells me it was as rare as I thought for a stock 5.0 to run that quick. That was on regular street tires. No Drag radials

low 13.90’s is definitely a good one, coupes were a little quicker than gt’s being a couple hundred lbs lighter, but yes that’s one of the good ones. My 90 ran 14.05/.10 before we started putting stuff from my gt on it.

It ran 13.20’s before putting heads and intake on it, that was gears exhaust and a little baby b cam and 1.7’s.

great post, I think a lot of that has to do with the model of the mustang as well, let’s use 92 for example. Take a 92 mustang GT loaded probably weighs close to 3400-3500 pounds, then take a 92 coupe base model, crank windows no back seats and your gonna save 500-600lbs

Yes the coupes were on average - few tenths faster due to being lighter. I used all gt’s in my example to Keep it even and only ones I drove myself at the track to keep hearsay and driver variables out.

Coupes also mostly came with 3.08 gears vs the 2.73 in most gt’s so there is that too.

Every nkw and then youd see see one with 3.27’s in a 5 speed, but not often. 3.27’s mostly came in auto cars if they didn’t have 2.73’s or 3.08’s.

[patchesII]

Kevin's was a 5 speed and clean clean. He should've kept it

[90 5.0]

Kevin's was a 5 speed and clean clean. He should've kept it

I regret selling mine, but it had become a full blown race car and I was out of racing and my buddy wanted to try and run the class I built it for again(nmra pure street) and then he moved for work arg.

Anyway a clean 5 speed coupe these days is hard to find and you’ll pay for it when you find one

getting out of racing cars and now I race a prostock boat, somebody explain thatvone to me LOLOL

[vnemous]

[Motv18]

Being a mercury thread their should be pics of vetts with merc made heads not women’s daily drivers.