Mercruiser 3.0 rough idle at start and stumbles momentarily during acceleration

[fourtwenty]

I have a 2001 Bayliner 175 with Mercruiser 3.0L engine. Does not have TKS. Bought it last fall, have had it on the water since late May. It drives well enough that I feel comfortable using it for cruising around the lake, towing tubes and water skiers etc. It will cruise all day at 35+ MPH without issue.

#1
When I start it from cold I have to give it throttle to get it going. It won't stay running if it's below ~1200RPM. After a minute it's fine and idles around 700RPM. Probably a choke thing?

#2
When accelerating, I give it throttle and it winds up to ~2200RPM. Then it starts to stumble, drops down to ~1600RPM then seems to clear itself out and then the RPM climbs to around 2800RPM. I then start increasing the throttle again. As soon as it starts to stumble I stop increasing the throttle. I don't reduce it, just leave it until it goes back up. In the attached video you can see I throttle up to around 2200RPM. It bogs down then winds up to ~2600RPM. I then give it more throttle without any issue. Flooding or starving?

Things I have done:
fiddled with idle screw and mixture screw per what I have read on these forums to get it idling nicely at 650-700 RPM at in gear idle, while on the water. I used a proper tach for this, not the one on the dash.
Check the accelerator pump performance (while motor is off). I can see a steady squirt of gas which is what I read there should be.

Any ideas what to look at next? Think these 2 things could be related?

 

[alldodge]

Most likely it needs the carb rebuilt, but there is also a issue with the electrical system. Watch the fuel gauge it pegs full then drops to empty and then back up. Might be a bad ground

Clean both ends of all battery cables including the grounds (both ends)

 

[fourtwenty]

Most likely it needs the carb rebuilt, but there is also a issue with the electrical system. Watch the fuel gauge it pegs full then drops to empty and then back up. Might be a bad ground

Clean both ends of all battery cables including the grounds (both ends)

Thanks, I figured it might just need a new carb. Any suggestions on where to get a rebuilt one for a reasonable price? I rebuilt a carb once many years ago and the vehicle wouldn't run when it was raining so I don't think I want to try that again lol.

I'm chalking the fuel gauge thing up to a bad sending unit. Once the tank is about half-empty it doesn't register anything. I was going to look into that but it's lower on my priority list. I will check and clean the battery cables but they were fine when I checked them last fall when I got the boat.

 

[alldodge]

Haven't bought a carb in many years, I would just search for "Mercruiser TKS" or search by part number 8M0084193 to see what shows up

 

[fourtwenty]

Haven't bought a carb in many years, I would just search for "Mercruiser TKS" or search by part number 8M0084193 to see what shows up

It's not a TKS. Found 807504N on the carb, presumably I can use that to find something.

 

[CaptnKingfisher]

Thanks, I figured it might just need a new carb. Any suggestions on where to get a rebuilt one for a reasonable price? I rebuilt a carb once many years ago and the vehicle wouldn't run when it was raining so I don't think I want to try that again lol.

I'm chalking the fuel gauge thing up to a bad sending unit. Once the tank is about half-empty it doesn't register anything. I was going to look into that but it's lower on my priority list. I will check and clean the battery cables but they were fine when I checked them last fall when I got the boat.

I just replaced a Rochester carb on my omc 2.3 l. There weren't a lot of companies carrying that carb so I took a risk and ordered from flying fish carburetors (even though I read a couple negative reviews on this forum). But my experience was great, the carb arrived a week later and seems to be rebuilt perfectly. They also have a policy where they'll give you a paid for return shipping label and you can send em your old carburetor and get $68 refunded to you. They'll rebuild that carb for the next guy. I definitely would recommend those guys based on my experience

 

[alldodge]

807504A1 is a Merc carb

 

[Kubaat3lover]

Same issue with my V6 4.3L MerCarb when cold,
Im after carb rebuilt, boat runs great when cold, hot etc..
idle + mixture adjusted according to spec but..
it happens only when cold, 1st start of the day, it started immediately but when i do not keep 1000-1500rpms but put it on idle, RPMs are quite low and the blackish smoke is coming from the water, after a while its fine. the RPMS are higher, I can shut it off and start immidately.
On hot warm days there is no issue, only now when the temp was around 73*F
I will follow this thread
Take care

 

[fourtwenty]

I'm not finding much in the way of the mercarb for sale for a reasonable price but I have come across a few places claiming a rochester carb as a direct replacement, also with claims it's better than the mercarb. Anyone have thoughts on that?

 

[alldodge]

Rochester 2GC is a good carb and use to be on the Merc motors.