Outboard drag boats, why are there no 4-strokes?

**Brad Zastrow** · 06-12-2019, 09:42 AM

I can not think of any other motor sport where 2 strokes are the norm other than outboard drag boats. Why is that? I know everyone will say 4-strokes are too heavy. However Mercury's new 4.6 liter V8 four stroke weighs the same as the Mercury 3 liter 300XS. A 4.6 liter 4-stroke with a supercharger can easily make 1000hp with only a 250 pound disadvantage at most. Drag 2-strokes make 400-500 hp at best? Seems to me the big torque (aka acceleration) and hp of 4 stroke is what will propel a drag boat even faster/quicker despite the additional weight. Maybe it is the cost to develop or the newness of the 4.6L Merc. A Speedmaster lower on a light boat with a 1000hp could work on a drag boat. I would love to hear thoughts on this.

**AZMIDLYF** · 06-12-2019, 10:08 AM

My guess is that it is a little ahead of the development curve right now. Cost will play a part though.

**mach351** · 06-12-2019, 10:11 AM

Weight and RPM. Remember drag motors can see close to 11,000rpm. It’s a simple matter of math when you’re dealing with a single speed power delivery. If you had more “gears” a four stroke would start to work, but then you’ve got the added weight. It’s tough to top a 375 pound 375hp 11,000rpm drag motor when your boat weighs less than 1250lbs with you in it.

**Whaaaaat** · 06-12-2019, 10:11 AM

How many 300xs motors you see drag racing?

**mach351** · 06-12-2019, 10:22 AM

Originally Posted by Whaaaaat

How many 300xs motors you see drag racing?

None

**Whaaaaat** · 06-12-2019, 10:25 AM

None is what I thought. Plus the car motor boats have there own drag racing class.

**JPEROG** · 06-12-2019, 10:26 AM

Weight is everything with such a short course. Stretch the length to 1000 feet or 1/4 mile and it would be a different deal. I learned this with the sand drags (300 ft.)-light weight buggies and rails were hard to get around even with blown big H.P. and four wheel drive but we could run them down hard and would have sling shoted by most of them if we had another 200 or 300 feet of strip to play within.

Joe

**mach351** · 06-12-2019, 10:57 AM

Originally Posted by JPEROG

Weight is everything with such a short course. Stretch the length to 1000 feet or 1/4 mile and it would be a different deal. I learned this with the sand drags (300 ft.)-light weight buggies and rails were hard to get around even with blown big H.P. and four wheel drive but we could run them down hard and would have sling shoted by most of them if we had another 200 or 300 feet of strip to play within.

Joe

this is exactly right. Anyone want to see it in action, come to a race and watch Casey in the big Monty V8, weighing 100’s of pounds more, go up against a 2.5. That 2.5 will get out on him, but by the end of the 800’ that 700hp V8 is coming on like a freight train. The big OMC V6’s do the same. Andy Driver used to tell me Dave Bush would go by him so fast at the end of the course that it would peel his numbers off lol.

**Capt.Insane-o** · 06-12-2019, 01:07 PM

Prolly when someone buys a 30k motor, drops another 30k on modifying it with non existent parts and still gets their ass handed to them at the drop of the light by a 30 year old two stroke.

**Brad Zastrow** · 06-12-2019, 03:25 PM

I did not say 300XS is a race motor. I am stating that the new 4.6 four strokes weigh what a 3 liter two stroke weighs. Sorry I am not buying the logic about the light weight being everything in drag racing. Why are there no two stroke dirt bikes? Dirt bikes are all about acceleration and weight. No two stroke drag motorcycles? The fastest snowmobiles by far are four stroke turbos even in 500' races. The 4 stroke snowmobiles are heavier than the two strokes but the difference in ET and speed is not even close. I get the one speed (no trans) thing also which is why a SC 4 stroke with all the low end torque should really shine vs the two stroke with porting for 11,000 rpm with no low end torque. So again I ask why not a 4 stroke? I think time will change that.

**nitro_rat** · 06-12-2019, 03:32 PM

Originally Posted by Brad Zastrow

Sorry I am not buying the logic about the light weight being everything in drag racing.

Build a 4 stroke drag boat and prove everyone wrong

**Brad Zastrow** · 06-12-2019, 03:38 PM

I have no skin in this game at all. I think there is an opportunity to raise the bar. Here is the last big engine I had built 1300hp.

**Capt.Insane-o** · 06-12-2019, 04:01 PM

The watemelon sized gearcase isn't going to help matters either

**CUDA** · 06-12-2019, 04:26 PM

ODBA tried a green class ten years ago, very few showed...

It is a real commitment to get involved, very few do.

All you need is for 5 -6 boats to show every race.

That's the hard part.