Racing Mark 55 Carbs

**Why Not** · 06-24-2021, 09:18 PM

I have a mark 55 and it mite need smaller carbs, here's a list of when we have, KA7A which is on in now and these a the spares/parts KA13AT and KA2A. Im the 3rd user of this boat and my dad said he hard the hardest time getting to to run (he cant remember what was wrong). Would smaller carbs help? Still have not got it running yet, has no spark so we will clean the points in the morning and see what it does.
Edward

**mrichartz** · 06-25-2021, 11:31 AM

Did he have it running and just pain to start? Carbs....?
Once you get spark and hopefully running will be easier to get an idea ..how it runs will give you an idea...will need to check the plugs and pistons to see if it's running rich etc.
Hopefully just need to clean it up to get spark..

**Why Not** · 06-25-2021, 02:21 PM

He had it running and used it a bit, it was the engine that was used when it raced. I'm doing gas lines while my dad does the points, then we will see what it does. I will post if it fires up. The high speed/main jets were set at 1 1/4 is that good?

**staylor** · 06-25-2021, 05:24 PM

I think your carbs are OK for the Mk55. I recall I ran the KA7A on my Mk55 way back when. If you've got the Fairbanks Morse mag on it rather than the later Kiekhaefer the point gap is very small, .008 -.010 or it won't fire very well. Point gap is the same for the Kiekhaefer mag but its not as sensitive. Be very careful of the rotor on the Fairbanks Morse- they are subject to cracking when removed or installed. I went through 4 of them on my MK55 before I found one that didn't crack on install- even after putting it in hot water for awhile. One and one half is a good starting point for the carbs. Run flat out and lean mixture until you just feel a slight drop in rpm and then open 1/2 turn. Usually you end up at 1 and 1/4 after doing this. Plugs should be J6J Champion gapped .025
Doug

**Dave S** · 06-25-2021, 05:52 PM

HeHee..... 40 bTDC........al else.....Phifffytttt.....wind down the carbs.......till it goes,,,,,,,

**Why Not** · 06-25-2021, 08:56 PM

Originally Posted by staylor

I think your carbs are OK for the Mk55. I recall I ran the KA7A on my Mk55 way back when. If you've got the Fairbanks Morse mag on it rather than the later Kiekhaefer the point gap is very small, .008 -.010 or it won't fire very well. Point gap is the same for the Kiekhaefer mag but its not as sensitive. Be very careful of the rotor on the Fairbanks Morse- they are subject to cracking when removed or installed. I went through 4 of them on my MK55 before I found one that didn't crack on install- even after putting it in hot water for awhile. One and one half is a good starting point for the carbs. Run flat out and lean mixture until you just feel a slight drop in rpm and then open 1/2 turn. Usually you end up at 1 and 1/4 after doing this. Plugs should be J6J Champion gapped .025
Doug

We got it to run! The points were barely opening and it started up 2-3 pulls. It has the later Kiekhaefer and opened the gap (more then .010) mite close it some later on, my dad caught the fever (putting old engines together) we just grabbed my grandfather (gold colored) Merc and he is very excited. It has the stacks cuzs that's the engine he used with the racing lower unit and he's sure his dad was NOT happy being the first brand new mark 55 he bought. That's the next project. Were going to Lake Gorge (between silver bay and sabbath day point) I'll get some vids and post them.
Edward

https://streamable.com/pdt5tq

https://streamable.com/8ik3et

**Why Not** · 06-25-2021, 08:57 PM

Originally Posted by Dave S

HeHee..... 40 bTDC........al else.....Phifffytttt.....wind down the carbs.......till it goes,,,,,,,

Have have no idea what you said, it make me laugh at the end

**mrichartz** · 06-25-2021, 09:25 PM

Nice sounds good so far...now get it mounted and run it nice flat glassy day and go!

Thanks got me itching to get to mine and get it up to the lake just have a couple things to do.......

**Why Not** · 06-26-2021, 07:10 AM

Originally Posted by mrichartz

Nice sounds good so far...now get it mounted and run it nice flat glassy day and go!

Thanks got me itching to get to mine and get it up to the lake just have a couple things to do.......

Thanks, what do you have for a boat? The weekend of the 4th we will be at the lake and trying it out, mite be faster then an old Gold Cup (Scotty-Too G-27) race boat we have up there. Must say I'm very excited.
Edward

**mrichartz** · 06-26-2021, 08:26 AM

Originally Posted by Why Not

Thanks, what do you have for a boat? The weekend of the 4th we will be at the lake and trying it out, mite be faster then an old Gold Cup (Scotty-Too G-27) race boat we have up there. Must say I'm very excited.
Edward

Tachs have to get them adjusted or just put the old ones back and a few other small things just had so much other crap going on.
Good luck get out early for some flat water and have fun!
Don't forget videos..lol