7 petal?

[David - WI]

A "stock" 2.5L 260 turns 7500, the 280 turns 8200 rpm and a 300 Drag goes 11.5k... but only because the 2.5L "behind-the-liner" port layout is far superior.

[LakeFever]

I’ve never seen or heard any direct comparison between the promax and 260 blocks porting behind the liner. The exhaust chest between the 260 and 225 promax looks very similar if not the same by my eye. The sleeve porting is different on the 260 and rod slots are bigger but that’s all I can see that’s different in the block itself. The front half/horn intake, the cylinder porting and of course nic sleeves are the big differences

Mercrazy a 225 promax can turn 7000 easy with some added compression and a performance ecu. Powers, brucato etc

[mercrazy]

I’ve never seen or heard any direct comparison between the promax and 260 blocks porting behind the liner. The exhaust chest between the 260 and 225 promax looks very similar if not the same by my eye. The sleeve porting is different on the 260 and rod slots are bigger but that’s all I can see that’s different in the block itself. The front half/horn intake, the cylinder porting and of course nic sleeves are the big differences

Mercrazy a 225 promax can turn 7000 easy with some added compression and a performance ecu. Powers, brucato etc

This is going to be a FF build with carbs. I’ve already opened the exhaust dump in block and plate. I’m still leaning towards 7 petal if I can find a front half. Can’t decide if I want to attempt converting a 5 petal to 7.
I'm old and want to get away from computers, sensors, and electric pumps. Just want a reliable engine that I understand when something goes wrong.

[LakeFever]

Carbs I would try the fishing motor four or five petal first for two reasons. First having a strong vacuum signal makes tuning exponentially easier. Second you won’t face the same rpm limits that efi has and I know the four will turn past 7000 no problem. A good tight tune up with carbs really doesn’t have the same handicaps that efi does. In fact if possible I’d use the EE style five petal blocks I think they might make more power than the big four with carbs. If you get your compression up to 145psi and run premix I don’t think you will need much else to make that motor scream. How heavy is your boat?

[mercrazy]

Carbs I would try the fishing motor four or five petal first for two reasons. First having a strong vacuum signal makes tuning exponentially easier. Second you won’t face the same rpm limits that efi has and I know the four will turn past 7000 no problem. A good tight tune up with carbs really doesn’t have the same handicaps that efi does. In fact if possible I’d use the EE style five petal blocks I think they might make more power than the big four with carbs. If you get your compression up to 145psi and run premix I don’t think you will need much else to make that motor scream. How heavy is your boat?

1000lbs.
what are EE style 5 petal? the 5 petal in most older engines?

[XstreamVking]

Back when I ran carbs, I added velocity stacks. Smoothed the airflow and were well worth the money.

[LakeFever]

1000lbs.
what are EE style 5 petal? the 5 petal in most older engines?

If you look at the available aftermarket reed valves on the market you will see there are many different styles. The latest fishing motor five petal was the 2.5 200 EE block which is the preceding unit to the four petal FF. I have no idea what motors these five petal configs were used on prior to the EE so that would be my focus if I was building a carb five petal I’d aim for the intake and reed combo from one of those. Carbs maybe too to make it easy to start with in terms of jetting but I don’t know what the best carbs to run are. You’ll have to do some digging there if you want to figure out the best combo. I always take the approach of following a proven recipe, or starting with an oem configuration and modding one mod at a time to reach my goals. Tedious but effective. Plenty of 2.5 EE carb parts out there cheap too

1000lbs ain’t too bad. Wouldn’t scare me off a seven petal build at that weight. Hard to say if it’s worth the cost and effort vs returns. Lots of variable to consider. If I had a seven petal I’d probably just start with it if I was looking for a winder. A fun ripper I’d probably aim at the five. If I didn’t already own the seven petal I’d probably start with the five and see what I could get out of it. Then finally if I had a four petal intake and carb set up in hand I’d use that first. It’s all about what I have vs what I would buy. Kinda like my first build I basically used all the things I already had to put this together. Bought some fancy tdr reeds and a new ecu and that’s it. Everything else is what was on my motor. The new motor now that I have some insight into this process is getting a lot more mods. Seven petal etc.

[mercrazy]

Is the 4 petal that buckshot sells the same size/bolt pattern as the stock 4 petal?
Or, are all 4 petal and 5 petal the same length and will bolt up to regular 4 petal intake?
I can’t tell from pictures how long they are.
Is 7 petal the only one that goes all the way across the intake?
Thanks for all responses. Sorry I’m so dumb.

[skialot2]

From the information I have collected while doing my own FF build. If you are building a Crab or Laser EFI motor, Stick with the 4 or 5 petal fronts. The 4 petal are supposed to flow slightly better. The 7 petal reeds are better suited to the high performance EFI motors. Even though they did make some 7 petal carb/laser motors. Just what I have heard, not from personal experience.

[LakeFever]

The four and fishing motor five petal fit the smaller staggered intake. The seven petal and the big five petal are full width and do not fit in the smaller intake. The four petal is the latest iteration of the smaller width reeds. The five petals were earlier models

[Merc 2.5]

Most of the 240 sport jet came with big 5 petal cages ( same length as 7 petal) the small 4 and 5 petal dont fit. I run a ported , compression, the works 240 sport jet on my bass boat converted to small front half (4 petal) with big bore carbs and turns my 28 chopper 7k rpm. But again theres nothing on the motor thats stock or un touched

[LakeFever]

Why did you convert to the smaller four petal front half?

[Merc 2.5]

Went with carbs and didn't really plan on turning 7k+ id sure like to test a 7 tho