BoatingLab Director Randy Vance and Boating contributor Charles Plueddeman pit Mercury's new 4.5L sterndrive versus GM's 5.0L sterndrive in a drag race.
Maybe I missed it, but was the race against the other boat a 5.0mpi, or a 5.0tks? thats a 40hp difference between the two v8's. Torque should be about the same, but efi tends to level the torque curve better than carbs. Also, what was the drive ratio of the sterndrive? What about the props? How much fuel was in each boat? Those are the numbers I want to know during a test. I like the fuel mileage tests I've seen, but I find it hard to believe that a v6 that has fewer horsepower and less torque outperforms a small block v8 on power to weight ratio alone.
I saw other tests that the 4.5 v6 out-accelerated the v8 to 35 mph (no surprise there as the 5 liter v8 is notoriously slow in acceleration--at least the carbureted versions) but the v8's top speed was 4mph faster. I also notice that the bore of the v6 is 4 inches--the same as the GM engine so I don't really believe that this is an original design by Mercruiser. What's the firing order? I'll bet it's the same as GM 4.3L. What is the angle between the banks? If it's 90 degrees that's the same as GM which means you'll have rough engine at times and inconsistent acceleration due to uneven firing intervals. For me there's no substitute for a V8 5.7L in marine applications except the 6L v8 300hp. You get both low end torque and top speed with these engines. It's pathetic to see boat manufacturers go to such tiny engines---only a few offer the 6L engine in a 20' size boat.
do a bit more home work. i know what ur saying. iv owned a 4.3 and been a mechanic many years. im sure merc held on to some things as lessons learned over the years but they changed a hell of a alot.
buy the way i own a 2.5 200hp version. love it. the light weight fly wheel is a bang on idea and i can do 45 mph and talk to some one on the other side of the boat love to see that in a v8 boat
Well 45mph doesn't impress me at all... it's 2017 not 1965... though I suppose that's pretty good for 200hp I/O. Surprises me that it's so quiet as larger displacement with same number of cylinders usually means more noise. Merc makes a big deal about moving the intake to the back of the engine---only thing is a lot of boats have vents back there and if water comes up (i.e. on a sudden slowdown from planning to idle on a choppy day) the water might come up the transom through the vents, hit the intake and snuff the motor out like a candle. As far as homework I'm trying but can't find out any info on the firing order and the engine sure looks like a 90 degree V6---a prescription for roughness if there ever was one, especially with a light flywheel... When one spends $50k+ on a boat one expects refinement and smoothness... Maybe a 60 degree V6 would be too tall, especially with increased stroke to get to 4.5....Merc should have built a 4.6 -- 4.8 liter V8 instead...would have gotten 260-280hp which is what 20'-22' boats need ..... 250hp is barely adequate unless it's a Regal (stepped hull) or ultralight boat like Bayliner or Stingray...
One other thing I've heard is that high performance designers won't touch this motor, which indicates that 250hp is right at the maximum of power possible, which has adverse indications for reliability and longevity, and with barely adequate power it's going to be working much harder more often than the 5.7L V8 did....
@@lbill4637 No it won't. Unlike cars this makes its power from displacement, not turbos. I'd rather have a Merc block in a boat, just like I'd rather have a Chevy block in my truck.
Nice video! Very happy with my 5L MPI but pleased to see the 4.5 run hard. Should plane a bit quicker for skiing w/ less weight. The 4.5 is unbalanced at 90 degrees so Merc included the GM balance shaft which has been trouble free. I'll buy it, especially as the Volvo/GM alternative is direct injection which I don't want on my boat.
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Maybe I missed it, but was the race against the other boat a 5.0mpi, or a 5.0tks? thats a 40hp difference between the two v8's. Torque should be about the same, but efi tends to level the torque curve better than carbs. Also, what was the drive ratio of the sterndrive? What about the props? How much fuel was in each boat? Those are the numbers I want to know during a test. I like the fuel mileage tests I've seen, but I find it hard to believe that a v6 that has fewer horsepower and less torque outperforms a small block v8 on power to weight ratio alone.
Mercury only cast the heads not the block.
Nice real world performance comparisson. But the GM is a 4.3 not a 4.0
I saw other tests that the 4.5 v6 out-accelerated the v8 to 35 mph (no surprise there as the 5 liter v8 is notoriously slow in acceleration--at least the carbureted versions) but the v8's top speed was 4mph faster. I also notice that the bore of the v6 is 4 inches--the same as the GM engine so I don't really believe that this is an original design by Mercruiser. What's the firing order? I'll bet it's the same as GM 4.3L. What is the angle between the banks? If it's 90 degrees that's the same as GM which means you'll have rough engine at times and inconsistent acceleration due to uneven firing intervals. For me there's no substitute for a V8 5.7L in marine applications except the 6L v8 300hp. You get both low end torque and top speed with these engines. It's pathetic to see boat manufacturers go to such tiny engines---only a few offer the 6L engine in a 20' size boat.
do a bit more home work. i know what ur saying. iv owned a 4.3 and been a mechanic many years. im sure merc held on to some things as lessons learned over the years but they changed a hell of a alot.
buy the way i own a 2.5 200hp version. love it. the light weight fly wheel is a bang on idea and i can do 45 mph and talk to some one on the other side of the boat love to see that in a v8 boat
Well 45mph doesn't impress me at all... it's 2017 not 1965... though I suppose that's pretty good for 200hp I/O. Surprises me that it's so quiet as larger displacement with same number of cylinders usually means more noise. Merc makes a big deal about moving the intake to the back of the engine---only thing is a lot of boats have vents back there and if water comes up (i.e. on a sudden slowdown from planning to idle on a choppy day) the water might come up the transom through the vents, hit the intake and snuff the motor out like a candle. As far as homework I'm trying but can't find out any info on the firing order and the engine sure looks like a 90 degree V6---a prescription for roughness if there ever was one, especially with a light flywheel... When one spends $50k+ on a boat one expects refinement and smoothness... Maybe a 60 degree V6 would be too tall, especially with increased stroke to get to 4.5....Merc should have built a 4.6 -- 4.8 liter V8 instead...would have gotten 260-280hp which is what 20'-22' boats need ..... 250hp is barely adequate unless it's a Regal (stepped hull) or ultralight boat like Bayliner or Stingray...
One other thing I've heard is that high performance designers won't touch this motor, which indicates that 250hp is right at the maximum of power possible, which has adverse indications for reliability and longevity, and with barely adequate power it's going to be working much harder more often than the 5.7L V8 did....
@@lbill4637 No it won't. Unlike cars this makes its power from displacement, not turbos. I'd rather have a Merc block in a boat, just like I'd rather have a Chevy block in my truck.
Id rather have a GM built engine.
sms373 they were never gm built
Nice video! Very happy with my 5L MPI but pleased to see the 4.5 run hard. Should plane a bit quicker for skiing w/ less weight. The 4.5 is unbalanced at 90 degrees so Merc included the GM balance shaft which has been trouble free. I'll buy it, especially as the Volvo/GM alternative is direct injection which I don't want on my boat.