Merc best 2,5's

[ToffenG]

Hi!
After this season I will convert from a single Promax 300 SVS to a twin Merc 2.5's. It proved to be too heavy to hang two PM 300 SVS on my ol' Phantom. The boat builder advised strongly two 2.5's due to the balance of the setup.
A guy in UK runs a similar boat with twin Merc 2.5 SS (280 HP and 15 inch mids) engines, and top speed is in the upper 90-ties.
I do not know so much about the Merc 2.5 other than one is 260 HP and one 280 HP. I am looking for the best version into longvity, and the possibility to tweak to 300 HP.
If I am correct the brucato PCU can not be used on latest version of Merc 2.5 (280 HP). Is is easy to change the electronics into 260 version, allowing the use of the PCU? Can SVS Intake be used on the new version 2.5?
Or should I go for a Merc 2.5 (260 HP), add a SVS Intake and a PCU? I presume I need a new alternator then?
Down to basic. Which is the best engine? Max rpms should be 7500.
Cheeeers and thanks,
Toffen G

[STV_Keith]

Well, there is more info about this kind of stuff over at http://www.screamandfly.com , but the general concensus is:
The 260's run hard, and can be modified to 300+hp. SVS is available, as is the Brucato PCU for tuning. Standard 16amp charging system.
The 280's run harder, but have the 40 amp charging system with the big external alternator, and have a rev limiter built in at 7850 I believe.
The 300 Drag's make 300+hp stock, but won't live as long. They will turn up to 10,000rpm and above though, in stock form.

[Tom Brown]

I haven't changed the fuel curve on a 2.5 but am about to. From what I read, it isn't something that is 'easy' to do, although the Brucato PCU looks to be the easiest.
Also, I think the benefits of moving away from the stock computer go up as you modify the engine. My engine has been heavily cut so I'm hoping to make it run better with Wayne Taylor's MAD EFI system.

[randy77zt]

i think the last 260's were made in 97 or 98.all 280's after that.the 280's have a charging system.the offshore race version has a higher rev limit in the ecm.2 stock 280's with good props and set up should work fine.if you can find a pair of motors that counter rotate.check the mercury website for specs.

[W. Tripp]

New 260's are no longer available complete from Mercury, but rotators and Drop-ons are.
The 280 is a great engine with the standard 7700 rpm rev limit, the Offshore Race limit 8250 rpm or with the limiter removed for up to 8700+ rpm. And the charging system is a great addition. If you want more rpm than this, only then would I recommend going to 260/Drag electronics. The 280 comes with more compression than the 260 ever did. The SVS will not work with the standard 280 since it doesn't have provisions for a throttle position sensor. If you convert to 260 electronics, the SVS will work well, as will the Brucato PCU.
If you are interested in buying complete new engines - act fast. The 280 will be going out of production this summer.
I hope this helps,

[STV_Keith]

Wayne, what else did they do in the 280's to allow those to run more compression without the detonation problems compared to a 260?

[W. Tripp]

The 280 is basically the Drag engine block with 260 sleeves. The port timing is mid range for the 260 and not as high as some of the later 260's. The block has the same improved exhaust chest as the Drag engine but without all of the hand blending and matching. The heads use an o-ring in place of a composite gasket, just like the 2001 and later Drag engines. The ECU map also runs a bit richer at part throttle. The 280 Race Offshore has a better map for performance use as it is a bit leaner in the low to mid range. Rapair uses this map when they pull the limiter.
I have seen good running lake used 280's with over 160 psi from the factory that have run several seasons on pump gas without any detonation. It is my belief that the improved exhaust chest and o-ringed heads allow the 280 combustion chamber to run quite a bit cooler than the 260's and get away with more compression.
Despite claims to the contrary, a 260 cannot be ported to Drag specs due to the exhaust chest changes - the 260 is NOT the same block, and is missing some of the material needed.
I hope this helps.

[HavasuDreamin']

Originally posted by W. Tripp
If you are interested in buying complete new engines - act fast. The 280 will be going out of production this summer.
Say it aint so. :( :( :(

[W. Tripp]

The S3000 is gone, the 280 will be gone in just a few months, and the Drag is scheduled for termination next summer.
A 245 hp direct injected 2.5L will be the new "High Performance" engine with a proposed 7700 prm limit. Think of a 200SX with more rpm.
The EPA has told the manufacturers that any engine that shifts out of forward gear is NOT a race engine - the days of Mercury 2-stroke performance are numbered.

[HavasuDreamin']

Well if this isn't the most depressing thread I have read in a long time. :( I read about Merc's new 4-stroke in the most recent issue of the magazine. I have to say that I am impressed, but at 667 lbs., the transom life of a 19' tunnel has to be next to nil. Also, they mention low end hole shot and mid range a lot which we all know means no 7,500 rpm passes.
On the bright side, there were so many 2.5L motors made from 1992 - 2004 that Merc will have to carry parts and drop ons for a while I would guess. It shouldn't be hard to put one together even after new production has stopped.
HD

[W. Tripp]

I have heared rumblings of an inline 4 cylinder 4-stroke with a bigger bore than the Verado that will be supercharged and intercooled on a 12-15 inch midsection. This is intended to be the next generation racing and high performance engine.
If they can get the torque up with boost, and make a reliable 1.5:1 ratio final drive gearcase, this has REAL POTENTIAL. Look at what has been done with 2.0-2.3 liters in import racing. If they can make over 1100 hp, a wide TORQUE band 4-stroke can be a reality for an outboard.

[HavasuDreamin']

No doubt 4-stroke is the way of future. I guess it has to be because of the tree huggers. In its initial stages (including now IMHO), the motors have two major problems:
1. Too heavy.
2. Lower reving motors focusing on low end and mid range.
I do think that the Verado is a step in the right direction. I would love to see a 4 cyl. putting out 250 hp or so with a 7K limit weighing in at about 400 - 450 lbs.
That would kick a**. I definately see it coming, just when?

[W. Tripp]

Look at the weights of the new 150/175 hp Yamaha 2.67L (466 lbs) and the Suzuki 140 2.3L (400-425). This is with a 20 inch midsection. I do not like the geometry of the Honda outboards...rod to stroke is WAY off. But, Honda has 2.0 and 2.2 liter engines in the S2000 car that revs to 9000 rpm. Just add boost! The import drag racers are seeing 11-12,000 rpm in the naturally asperated classes.
I expect Merc's new racing engine to be available for the 2006 season. And there are rumors of a Toyota racing outboard that will rev to 20,000 rpm. I can't wait to hear that one run.
Overall, I think that 4-strokes will be a GOOD thing for our sport. Remember when cars started getting fuel injection? Everyone started crying "the sky is falling"....now look at where performance has taken us.
P.S. - Toffen, sorry to highjack your thread.

[sorry dog]

I guess we'll have to embrace them at some point but I'll still add a bottle of oil for the smoke effects. :D

[Maverick]

What brand of oil and what oil ratios are you runing in a 2.5 EFI???
I'm getting into a used boat and believe they were running KLOTZ.
What WOT rpms should this motor run ????
any thoughts or tech that I can review??
MAV

[VIKING]

Originally posted by sorry dog
I guess we'll have to embrace them at some point but I'll still add a bottle of oil for the smoke effects. :D
Good one sorry dog:D
My wife wants me to get a I/O she hates the noise and the smoke. BUT I LOVE THE SPEED!!!! pound for pound it's tough to beat a outboard:p
Mave, I use Amsoil 100:1 on all my 2 strokes and have NEVER had a lube problem even with NOS.

[HavasuDreamin']

Originally posted by Maverick
What brand of oil and what oil ratios are you runing in a 2.5 EFI???
I'm getting into a used boat and believe they were running KLOTZ.
What WOT rpms should this motor run ????
any thoughts or tech that I can review??
MAV
Klotz KL-333 is good oil. Make sure to run a synthetic oil, what ever brand you choose. I don't know any one getting away with 100:1. That is way thin. I run 32:1 and have more than 7 seasons on my motor. Runs like a bat out of hell still.
You should see 7,500 RPM + out of a 2.5L EFI motor. Good Luck.

[Tom Brown]

Originally posted by W. Tripp
I expect Merc's new racing engine to be available for the 2006 season. And there are rumors of a Toyota racing outboard that will rev to 20,000 rpm. I can't wait to hear that one run.
They should get some of their engineers from that project over to the Formula 1 team. The Toyota F1 engine won't turn that fast and live.
Someone should do an unbiased performance comparison between the MAD EFI system and the SVS/PCU. I'm hearing of several racers dump their SVS in favor of the MAD EFI kit.

[Kim Hanson]

Whats a Merc? Oh, yeah that AZH's friend isn't it :D ........( . )( . )...