Merc 2.5. Why are they better?
09-02-2010, 12:50 PM
#11
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2.5 is the only legal outboard to race.
09-02-2010, 12:51 PM
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09-03-2010, 01:59 PM
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Never been a huge outboard fan myself, but the 2.5 does seem to be bad a$$.
You can see a couple in action here.
http://home.comcast.net/~corywurst/jasper05.wmv
You can see a couple in action here.
http://home.comcast.net/~corywurst/jasper05.wmv
09-03-2010, 02:06 PM
#17
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[QUOTE=Too Stroked;3198072]
Flywheel weight most certainly affects acceleration. Recall that acceleration is the rate of change of velocity or speed. The amount of mass (weight) is part of a property called mass moment of inertia and is dependent on the amount of rotating mass and the distance from the center of rotation of that mass (e.g. the diameter of the flywheel). The distance (diameter) is far more important than the amount of mass by the way. Inertia will not affect the ultimate top speed of the rotating assembly, only how fast it gets there.
Dan
Lightweight flywheels DO NOT help acceleration, only reduce the stress on the upper bearing, the gyroscopic effect at rpm is brutal. QUOTE]
Interesting. Doesn't the additional rotational mass (of a heavier flywheel) impeed a engine's ability to spin up quickly? "Snappy" is the best word I can apply to what a 2.5 EFI kick in the pants feels like. Yes, some of that is just raw horsepower, but some of that is the engine's ability to spin up quicker - isn't it?
Interesting. Doesn't the additional rotational mass (of a heavier flywheel) impeed a engine's ability to spin up quickly? "Snappy" is the best word I can apply to what a 2.5 EFI kick in the pants feels like. Yes, some of that is just raw horsepower, but some of that is the engine's ability to spin up quicker - isn't it?
Dan
09-03-2010, 02:42 PM
#18
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[QUOTE=BajaDan;3199257]
Flywheel weight most certainly affects acceleration. Recall that acceleration is the rate of change of velocity or speed. The amount of mass (weight) is part of a property called mass moment of inertia and is dependent on the amount of rotating mass and the distance from the center of rotation of that mass (e.g. the diameter of the flywheel). The distance (diameter) is far more important than the amount of mass by the way. Inertia will not affect the ultimate top speed of the rotating assembly, only how fast it gets there.
Dan
Thanks for that,
Neither a DEPAC dyno, nor Aim telemetry can detect ANY gain, in acceleration, or hp with a flywheel change..... or lighter rods, or lighter crank, wrist pins and pistons. There is NO performance gain. Considering my source spent several million last season and is winning the UIM F1 circuit..........
What IS gained is reliability, what most people don't consider is the gyroscopic effect a 6.5lb flywheel has on top of a powerhead. In rough water the motor is constantly moving around, the flywheel is trying to maintain it's course. Turns etc, really hard on the crank and it's upper bearing.
Anyhow, this is a tangent. The 2.5 is a BADASS motor, pound for pound extremely hard to beat.
Yes they are still avaliable, you can buy a complete dropon powerhead, complete mid, complete gearcase, and a cowling and have a complete 2011 motor. You can also as a qualified racer order a 280. None have a warranty though.
As for the 300x stroker, Eric Simon has done it but he isn't who I was thinking about. The 385~ hp that he made is about 40hp more than a std X. Pretty impressive, though what I was thinking about the 450hp version, it is 3.4l as opposed to the 3.2 or Eric, it also runs 2.5 hi-per electrics as opposed to the ProMax electrics that Eric used. Erics motor is likely very user friendly and reliable. The BIG hp mercs, the 2.5, 2.7, 2.8 and the big block 3.4 motors in true race trim are shockingly reliable if you use the right engine builder.
Flywheel weight most certainly affects acceleration. Recall that acceleration is the rate of change of velocity or speed. The amount of mass (weight) is part of a property called mass moment of inertia and is dependent on the amount of rotating mass and the distance from the center of rotation of that mass (e.g. the diameter of the flywheel). The distance (diameter) is far more important than the amount of mass by the way. Inertia will not affect the ultimate top speed of the rotating assembly, only how fast it gets there.
Dan
Neither a DEPAC dyno, nor Aim telemetry can detect ANY gain, in acceleration, or hp with a flywheel change..... or lighter rods, or lighter crank, wrist pins and pistons. There is NO performance gain. Considering my source spent several million last season and is winning the UIM F1 circuit..........
What IS gained is reliability, what most people don't consider is the gyroscopic effect a 6.5lb flywheel has on top of a powerhead. In rough water the motor is constantly moving around, the flywheel is trying to maintain it's course. Turns etc, really hard on the crank and it's upper bearing.
Anyhow, this is a tangent. The 2.5 is a BADASS motor, pound for pound extremely hard to beat.
Yes they are still avaliable, you can buy a complete dropon powerhead, complete mid, complete gearcase, and a cowling and have a complete 2011 motor. You can also as a qualified racer order a 280. None have a warranty though.
As for the 300x stroker, Eric Simon has done it but he isn't who I was thinking about. The 385~ hp that he made is about 40hp more than a std X. Pretty impressive, though what I was thinking about the 450hp version, it is 3.4l as opposed to the 3.2 or Eric, it also runs 2.5 hi-per electrics as opposed to the ProMax electrics that Eric used. Erics motor is likely very user friendly and reliable. The BIG hp mercs, the 2.5, 2.7, 2.8 and the big block 3.4 motors in true race trim are shockingly reliable if you use the right engine builder.
09-05-2010, 12:53 PM
#19
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Merc 2,5 EFI's
Hi!
I have been running twin Merc 2,5 EFI SS engines 280 hp each with Brucato PCU EFI boxes since 2006. Before that I used a Promax 300 single engines. The difference is out of this world. Now I am on plane in 1 (one) second. It accellerates from 48 mph - 80 mph in less than 3 seconds. And this is a 25 feet offshore V hull.
The Promax 300 is like BMW 5 series car. The Merc 2,5 EFI is like a Maserati.
A friend of mine has a Motion 25 cat with twin Optimax 250 xs. It runs more than 105 mph on top speed. He was coming in from behind in 80 mph, and when he was beside me, I dropped the footspeed - and bam I was in front of him. Great great fun.
The engines have been reliable. Parts are very cheap. But the total costs for me are too much, and the engines do not like to idle for too long due to no thermostats. And my wife likes to idle being able to drink wine and smoke. So now its back to a single engine again - Verado 350 sci.
Cheeers, ToffenG
I have been running twin Merc 2,5 EFI SS engines 280 hp each with Brucato PCU EFI boxes since 2006. Before that I used a Promax 300 single engines. The difference is out of this world. Now I am on plane in 1 (one) second. It accellerates from 48 mph - 80 mph in less than 3 seconds. And this is a 25 feet offshore V hull.
The Promax 300 is like BMW 5 series car. The Merc 2,5 EFI is like a Maserati.
A friend of mine has a Motion 25 cat with twin Optimax 250 xs. It runs more than 105 mph on top speed. He was coming in from behind in 80 mph, and when he was beside me, I dropped the footspeed - and bam I was in front of him. Great great fun.
The engines have been reliable. Parts are very cheap. But the total costs for me are too much, and the engines do not like to idle for too long due to no thermostats. And my wife likes to idle being able to drink wine and smoke. So now its back to a single engine again - Verado 350 sci.
Cheeers, ToffenG
09-06-2010, 12:57 PM
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[QUOTE=RBT;3199291]
Thanks for that,
Neither a DEPAC dyno, nor Aim telemetry can detect ANY gain, in acceleration, or hp with a flywheel change..... or lighter rods, or lighter crank, wrist pins and pistons. There is NO performance gain. Considering my source spent several million last season and is winning the UIM F1 circuit..........
What IS gained is reliability, what most people don't consider is the gyroscopic effect a 6.5lb flywheel has on top of a powerhead. In rough water the motor is constantly moving around, the flywheel is trying to maintain it's course. Turns etc, really hard on the crank and it's upper bearing.
Anyhow, this is a tangent. The 2.5 is a BADASS motor, pound for pound extremely hard to beat.
Yes they are still avaliable, you can buy a complete dropon powerhead, complete mid, complete gearcase, and a cowling and have a complete 2011 motor. You can also as a qualified racer order a 280. None have a warranty though.
As for the 300x stroker, Eric Simon has done it but he isn't who I was thinking about. The 385~ hp that he made is about 40hp more than a std X. Pretty impressive, though what I was thinking about the 450hp version, it is 3.4l as opposed to the 3.2 or Eric, it also runs 2.5 hi-per electrics as opposed to the ProMax electrics that Eric used. Erics motor is likely very user friendly and reliable. The BIG hp mercs, the 2.5, 2.7, 2.8 and the big block 3.4 motors in true race trim are shockingly reliable if you use the right engine builder.
Who's building the 450 3.4L MERCS???
Thanks for that,
Neither a DEPAC dyno, nor Aim telemetry can detect ANY gain, in acceleration, or hp with a flywheel change..... or lighter rods, or lighter crank, wrist pins and pistons. There is NO performance gain. Considering my source spent several million last season and is winning the UIM F1 circuit..........
What IS gained is reliability, what most people don't consider is the gyroscopic effect a 6.5lb flywheel has on top of a powerhead. In rough water the motor is constantly moving around, the flywheel is trying to maintain it's course. Turns etc, really hard on the crank and it's upper bearing.
Anyhow, this is a tangent. The 2.5 is a BADASS motor, pound for pound extremely hard to beat.
Yes they are still avaliable, you can buy a complete dropon powerhead, complete mid, complete gearcase, and a cowling and have a complete 2011 motor. You can also as a qualified racer order a 280. None have a warranty though.
As for the 300x stroker, Eric Simon has done it but he isn't who I was thinking about. The 385~ hp that he made is about 40hp more than a std X. Pretty impressive, though what I was thinking about the 450hp version, it is 3.4l as opposed to the 3.2 or Eric, it also runs 2.5 hi-per electrics as opposed to the ProMax electrics that Eric used. Erics motor is likely very user friendly and reliable. The BIG hp mercs, the 2.5, 2.7, 2.8 and the big block 3.4 motors in true race trim are shockingly reliable if you use the right engine builder.
