Promax 225 converted to carbs

**R.Allen** · 06-11-2015, 08:05 PM

Anyone ever done this? Ive got a 1998 225 Promax that was converted over to bare bones with carbs. I had a super mag that threw a bearing and was gonna have it rebuilt but saw someone selling a Promax with 10 hrs on it for the same price. It had sat for a year or so before I put it on my boat. it was built to be a racing motor had no thermostats, rev limiter or poppet. it was being run with an electric fuel pump also. So my problem is it doesn't run right. I put a mechanical pump on it and made it as stock as possible. Had the carbs cleaned and rebuilt and now it has a lean spit. Getting on plane is rough unless I hit the choke then it jumps up on plane. Once its up it runs like a top. What could be causing the lean problem? I changed all the fuel lines, water separator and ball. It has wh 28 carbs on it. Should it be rejetted since its being run with a mechanical pump instead of an electric? If so what jets?

**R.Allen** · 06-11-2015, 09:12 PM

Attachment 321267 Attachment 321268 Attachment 321269

**Dave Strong** · 06-11-2015, 11:47 PM

Jetting or and timing not right. Not sure why someone would take one of the best EFI motors Merc made and convert to carbs but thats just me. Steel sleeve motor with no stats or poppet even with diverters is an accident waiting to happen.

Dave

**1978allison** · 06-12-2015, 02:52 PM

I am running a set of wmh-2 carbs with timing set at 25 degrees.

**outasite** · 06-12-2015, 03:00 PM

What is your idle timing
set at? Should convert the cooling system back to t-stats and poppet,could be just a "cold sneeze"

**TEXAS20225** · 06-12-2015, 03:17 PM

225 promax has no bleed lines for low speed operation (87 wmh 2 are 150 carbs they must be jetted up to at least 245 specs

) too bad some body ruined a good mota in my opinion but im a EFI guy my self i hate carbs with a passion

**R.Allen** · 06-12-2015, 06:36 PM

i already put the thermostats back in (143) and poppet. havent checked any timing. im not that experienced with it. will try and figure it out this weekend. been looking online at how to do it but never found anything about this motor with it having carbs. i agree id also rather have efi but at the time it sounded like a quick fix to my problem. now has turned into a headache. 1978allison what jet set up are you running?

**dwilfong** · 06-12-2015, 07:08 PM

From the little I gather the 245 carbs have a larger air bleed tube in them. I have a few sets of 200 carbs and a few of the 245 pumpers. Thy have different air bleed tubes in them for the main jet tubes. Thy are a fixed tube sticking out in to the boar in front of the venture.
From this I would think that jets alone will not fix the problem.

**R.Allen** · 06-12-2015, 07:28 PM

Originally Posted by dwilfong

From the little I gather the 245 carbs have a larger air bleed tube in them. I have a few sets of 200 carbs and a few of the 245 pumpers. Thy have different air bleed tubes in them for the main jet tubes. Thy are a fixed tube sticking out in to the boar in front of the venture.
From this I would think that jets alone will not fix the problem.

Click image for larger version.

Name: photo.JPG
Views: 46
Size: 113.7 KB
ID: 321298

like this?

**Dave Strong** · 06-12-2015, 07:38 PM

Don't look like 245HP carbs no progression jets.

Dave

**R.Allen** · 06-12-2015, 07:42 PM

where do you get 245 carbs for this motor? can it be jetted to fix it. only at idle is there a problem. forgot to mention that before having the carbs redone we ran it on muffs and the bottom 2 cylinders werent firing at all. could pull the plug wires and nothing would change but there was spark. emptied the carb bowls and it fired up and ran fine then started happening again.

**Dave Strong** · 06-12-2015, 08:25 PM

225 Pro Max was never designed to be a carb motor, I'm sure its been done by someone but never dealt with it myself.

Dave

**dwilfong** · 06-12-2015, 09:15 PM

Those are the tubes I am referring to. Look like thy are the large ones. The 200 I have are necked down on the end the 245 look like the one in your pick.
The ones I have are WMH-7 pumpers. Thy are not listed as 245 carbs on any of the reference sheets.
But I was assured thy came off a 245. As it was told to me a 245 had a few different carbs. what ever was on the shelf as thy built them up thy would mod and make work.