Wmv carbs jetting on an FF block

**Kdybalski** · 08-16-2023, 01:13 PM

I have an ff block with 36 cc heads, exhaust porting, and rod slots cut. The factory has these carbs staggered/jetted all over the place and not sure if anyone has tuned them. I just built this motor and during breakin I bumped the mains 2 thousand. I’m attaching mercurys stock jet setting and pics of the plugs with maybe 7 hours on them. Double oil. Not sure where to go once breakin is complete. Should I just go back to stock?

**XstreamVking** · 08-16-2023, 01:53 PM

4 looks washed 3 and 6 look dry. 1 and 2 look good 5 has lots of buildup. jm2cts.

**Kdybalski** · 08-16-2023, 01:56 PM

Right, that’s what’s confusing. I took stock jetting and bumped 1 size up on main. The way mercury stock jetted the wmv 18 is a bit strange. Not sure to move jet sizes to with this read.

**Kdybalski** · 08-16-2023, 02:07 PM

Stock jetting call for 1-.80, 2-.82, 3-.82, 4-.80, 5-.84, 6-.78. My thought is to bump the mains on the two dry cylinders and check coil/wire on washed out cylinder first. Number 5 called for an 84 and under breakin in running one size larger jet than listed. Going to throw a new set of plugs in and have two hours left on breakin.

**XstreamVking** · 08-16-2023, 02:13 PM

Fat will not hurt the engine. And porting changes everything from stock. You run an airbox? What's the timing set at, and this is 'with 92 oct fuel?

**Baker343** · 08-16-2023, 02:37 PM

Not a wmv carb guy but you change the port timing and raised the compression.
I would run jets that keep your pistons and plugs a good color for the rest of your break in.
You will eventually do a WOT test pull and shut down to correctly read what each cylinder/piston needs.

**Kdybalski** · 08-16-2023, 03:15 PM

Stock air box on it. 92 octane. Timing set at 22, no advance box. Again, when I jetted the carbs I bumped all the listed numbers one size to make sure they were on the fat side during breakin. The pics show that stock jetting, plus one size, is not close. I’m going to check the one washed cylinder for coil/wire issues and place new set of plugs. I’m going to bump the two dry cylinders and maybe drop jetting in number 5. Any other suggestions. Mainly exhaust porting and the rod slot were cut. I milled the front half 60th and filled the void in block where oil pump shaft was. Carson reeds and 36 cc heads. The wmv carbs I’m just not use to with the odd jetting

**XstreamVking** · 08-16-2023, 05:50 PM

5 actually looks the most normal for a 25 to 1 oil mix. With the hi fuel burn rate of a BP the plugs will be wet when cruising and go clean at WOT.

**Baker343** · 08-16-2023, 07:33 PM

Curious, are you doing your breaking in on good old dinosaur oil and what is your compression after your current hours of break in. Fat and 22 degrees is always safe for break-ins.

**Baker343** · 08-16-2023, 08:46 PM

I would recommend finding carbs that you feel comfortable with when you decided to lean on it.
I'm a WH carb lover, but I've seen a lot of members recommending WMH specifically 21's for modified 2.5's like yours. I have recently purchased a set of WMH 30 AND 32'S for around 120.00 each.
The venturis are the same as the 21's and I plan to re-jet like the 21's. Blue goose has a lot of info on these carbs. You have a lot of time and/or money in your block.

**Kdybalski** · 08-17-2023, 05:14 AM

Originally Posted by Baker343

I would recommend finding carbs that you feel comfortable with when you decided to lean on it.
I'm a WH carb lover, but I've seen a lot of members recommending WMH specifically 21's for modified 2.5's like yours. I have recently purchased a set of WMH 30 AND 32'S for around 120.00 each.
The venturis are the same as the 21's and I plan to re-jet like the 21's. Blue goose has a lot of info on these carbs. You have a lot of time and/or money in your block.

I found a set of wmh 7’s with velocity stacks for 400$. I was advised that these came off a 245 motor. Any thoughts

**Kdybalski** · 08-17-2023, 05:22 AM

Originally Posted by Baker343

I would recommend finding carbs that you feel comfortable with when you decided to lean on it.
I'm a WH carb lover, but I've seen a lot of members recommending WMH specifically 21's for modified 2.5's like yours. I have recently purchased a set of WMH 30 AND 32'S for around 120.00 each.
The venturis are the same as the 21's and I plan to re-jet like the 21's. Blue goose has a lot of info on these carbs. You have a lot of time and/or money in your block.

Here is a pic of the wmh 7. Person selling says they came off a 245. No sure. My reference says merc 150.

**aj06bolt12r** · 08-17-2023, 06:15 AM

Hard to tell from the photo... But that's not aluminum glitter all over #5 plug is it? Does 5 still have good compression?

**Kdybalski** · 08-17-2023, 09:44 AM

It’s just the lighting on 5. When I pulled it I didn’t see any metal particles on the plugs, #5 included. Thinking just the lighting. I’m going to do a compression check today just to be sure

**Baker343** · 08-17-2023, 11:25 AM

Originally Posted by Kdybalski

Here is a pic of the wmh 7. Person selling says they came off a 245. No sure. My reference says merc 150.

Not sure if the wmh 7's came off a 260/245, maybe someone will chime in. I purchased wmh 30 & 32 to replace my wmh 3 pumper carbs similar I think to the 7's. I'm having issues with my 3's and want a simpler whm to go on my 91 2.5 family ski boat. I will rejet.

Search this post WMV-WMH carb info.
There's some charts showing different carbs and stock jeting