260hp to 245hp conversion

[WOT77]

Heys guys looking to convert my 260 hp pp motor to a carb 245hp. Just looking for some insight on things.
1. What carbs are best for this application?
2. Do I have to change or block anything on the reed/manifold/intake?

Any other insight that I am overlooking is welcomed.

Many thanks!

[rgsauger]

Welcome to the forum!

Did I actually just read that you want to go down in horsepower? :eek:

[WOT77]

You are correct. I know its unusual as most upgrade but it's more so what I have and am working with at this stage. It's basically a powerhead without intake. There's no efi or carbs on it and weighing out the cost for the whole efi system and considering I have sets of carbs just works with my budget at this stage. If only I knew what set would work. Any insight is greatly appreciated!

[mach351]

I ran carbs on a 280. Ran very good. Any set of 200 carbs will work. I personally used WHM-21’s. If you have an efi front half you have to either plug the injector holes, or leave the injectors in place and get creative with a custom carb linkage.

[rjdubiel]

What carbs do you have at the shop? WHM carbs with a 1.312 ventrui is what you want with the pumper or not. Or a WH carb like a WH 20, 22, 31, 46, all would work depending on what you are trying to do as WH carbs you have to be careful running half throttle if you jet them done to get on the line at WOT (lean in the mid range). I WH carbs on my 245 (carb 260) and ran 90+ jets (very fat all around) all the way down to 72 mains (only was down here for 800 foot drags, not on the lake or river).

Again what are you trying to do and what do you have for carbs will let the carb guys here know what you should run.

[David]

I thought that the 260s and 245s had the same porting. 15 HP from changing to EFI seemed like a lot. Was it that much?

[WOT77]

Thank you for your reply! That helps alot!

[tlwjkw]

in production form tha efi would turn higher producing higher horse power rating... so its believed... i liked tha carb version myself but back then ya didn't have tha adjustable/tunable electronics that developed later on.... tha 11350 that you could change tha chip in started tha whole thing....

[WOT77]

Honestly I don't know exactly what I have I'll have to take a good look and figure it out. The guidance that has been provided by yourself and others so far is very enlightening. I've been researching it and trying to pinpoint exactly what I need to do and your comments help to confirm some of the info I've been finding. I'll try and attach some screenshots of this info and posts so everyone can take a look at and maybe help rule out any false info and possibly confirm which info is correct.

Thanks again guys!

[rjdubiel]

Easiest is to take pics of what you got and find out what carbs you have and there are plenty of guys here that are willing to help you get it all set up weather you decide to run EFI or Carb!

[moatorbotin]

I thought that the 260s and 245s had the same porting. 15 HP from changing to EFI seemed like a lot. Was it that much?
I always thought they were pretty similar but the carb was derated to encourage EFI purchases.

[tlwjkw]

I'll try and attach some screenshots of this info and posts so everyone can take a look at and maybe help rule out any false info and possibly confirm which info is correct.

Thanks again guys!

port side, front and rear will work......

[WOT77]

512900512901

So this is some of the info I've come across. In one of the pics you can see it lists what carbs for different applications but it's not very specific as to what size for each 2.5l application. But with everyone's help here it is helping to narrow things down.

In another one of the pics is a s+f thread where it helps out with the jetting range for different applications (2.0,2.4,&2.5) Which rjdubiel has confirmed to be truthful and added his knowledge in his real life experiences. Thank you!

I'll dig through my stuff, take some pics and post what I have as he's suggested and hopefully I have a set that I can match up.

Thanks again everyone!

[WOT77]

Whm 21 I'm guessing?512905512906512907512908512909512910

[WOT77]

Wmv 16 I'm guessing?512911512912512913512914512915512916

[WOT77]

I didn't get your comment until I took the photos🤣😂 Thank you!

[WOT77]

I do have another set as well but can't get to them until tomorrow. Will post them when I get the chance.

[pkstv]

Don’t forget about the bleed lines needed . Here’s my 245

[25two.stroke]

I thought that the 260s and 245s had the same porting. 15 HP from changing to EFI seemed like a lot. Was it that much?

5 to 7 petal front...dont forget that. It was not as simple as carbs vs efi and everything else the same.

Sorry, what was I thinking yeah they all had 7 petal fronts...I guess I was thinking of promaxes with 5 petal fronts :rolleyes:

[WOT77]

Don’t forget about the bleed lines needed . Here’s my 245


Thanks for pointing this out. What carbs are on this setup? Is it a kk block?

[mach351]

5 to 7 petal front...dont forget that. It was not as simple as carbs vs efi and everything else the same.
245’s were 7peddle nic motors with identical porting to a 260

[mach351]

Don’t forget about the bleed lines needed . Here’s my 245
If he has a 260 block it won’t have bleed fittings on the cylinders. They can be installed but that’s usually more trouble than it’s worth. A better option for a carbs (or any wet-reed system like laser efi) is to connect all the bleed lines together into one line and run that back to the fuel tank. 1/8” line is sufficient. I’d recommend your “#1” set of carbs. Again, this is pretty easy to do…..your only real issue where you will have to design something is the throttle linkage. And efi linkage won’t work, and a carb linkage won’t fit an efi front half. If I remember right (it was a while ago) I spaced a carb throttle bracket out about 3/8” and then made a custom rod to the carbs out of 1/8 round stock.

[mach351]

Put #72 jets in the mains of those whm-21’s to start and you’ll be good. You’ll probably end up going down to a 70 or 68 eventually.

[mach351]

And you’re going to need a 2.5 7peddle carb intake if you don’t have one already.

[WOT77]

Thank you for all of your input Mach351! That is very helpful! I'll definitely be using your input 👍!