How To: Rebuild a Mercarb - Part 3: Adjustments

In this video, I will show how to make all the final adjustments and tweaks before putting the carb back on the motor. I will also cover the procedure for setting the correct idle mixture and speed when the boat is in the water. Stick around for the last of the mercarb rebuild series.
Check out my iboats thread here:
forums.iboats.com/forum/boat-...
Don't forget to like, subscribe, and tell a friend!
Thank you!

[@louispawlowich8869]

You Are the best. I am old and like working on these old engines. I just bought a 96 boat with a 4.3 Merck cruiser in it. The guy just before me thought he was a mechanic and even put things in backwards. The settings were all off and it is no surprise that the engine wouldn't run. Your tutorial was right on the money and you went above and beyond most people and included all the settings and why and how. Great job thank you

[@matthewwilliams1724]

I have NO questions...EXCELLENT tutorial, I just watched this and adjusted mine on the water per your instructions...EASY MONEY! Thank you.

[@ty84848]

Extremely great video. Thanks for posting. Excellent amount of detail and information. my 3.0 L mercruiser idles like a bag of sh1t and I think this video will really help save me loads of time getting the carb adjusted properly.

[@yannih1782]

What an awesome, helpful and detailed video. Thankyou for your time and effort. Sir, you are a champion...

[@MrTanzersailor]

Love it. Can't wait to adjust my carb in the water!

[@kylemoulton5606]

thanks for the great video series. more information the better imo. lots of info is left out of the service manuals and take real world experience to explain the thinking behind how these things are made.

[@e55_wagon]

Great video and great information! Thanks so much!

[@kubaSWAT]

Good video! I like your channel, I hope on Spring youll make a video on the water how to adjust! Im just finished carb rebuild process! take care

[@charlie1826]

Alot of great information

[@martingosek4903]

Awesome video! Thx for all the details...about to do mine on a 3.0... first time.

[@MadPropsMakes]

Thanks for watching and subscribing. The mercarbs are actually pretty simple once you have em apart. Good luck on your rebuild.

[@pole_barn_builder]

How did it end up going? Did it work out?

[@MrTanzersailor]

I rebuilted my carburator and noticed a that I was missing the filter, the ball and the clip of the acceleration pump although the spring is present. What are they supposed to do? You did a fabulous job with these videos. Looking forward for your next ones.

[@tilo1558]

Thank you so much

[@johnm98]

Thank you for the video! Been trying to set these with earmuffs on and not having much luck - can’t wait to try it in the water. Any idea if this is related to hard starting when the engine is warm? Forums suggest it’s flooding after shutdown, and throttling wide open when starting does in fact get it started. But the kicker is I rebuilt the carb and it’s still doing it..

[@jimhinds4727]

Great job on the video! I’m doing the same thing on a 1988 3.7 liter. Have you heard of the “thin” carb mounting gasket versus the “thick” gasket question/problem? I’ve got hot start problems now and hot idle trouble and trying to find a thick (1/4 inch) mounting gasket as the rebuild kit’s gasket was a very thin one. Hope yours runs well!

[@banderson2502]

Awesome video! Thank you! I did all the things you did, I think, and the boat idles great on start up, but then as soon as I move the throttle it runs great, until I disengage the throttle and then to restart the boat I have to reset the cam. It doesn’t stay in the same place once I unthrottle. Boat ran great until I replaced the impeller and a hose popped off and the bot over heated. Since then I can’t get it to idle without opening the things the cam adjusts... any ideas?

[@josephcomden6326]

Cannot say enough how simple you made it sound to a mechanically illiterate person. Thank you!

[@barry.anderberg]

I'm confused on the choke unloader - why would the throttle be all the way open when the engine is still cold and the choke plate hasn't started to open on its own already?

[@savichus]

But why you have added background music? It sounds like being placed on hold with at&t...

[@paucasal8904]

Ty for u video

[@leeh6816]

Great video and now subscribed. Followed the instructions and working great. Only problem is turning the idle screw anticlockwise doesnt have any effect on the idle and ive unscrewed it until its nearly fallen out. Assume something in that mechanism thats not working / broken?

[@andydavis6372]

Mine was didn’t that. I had to adjust my linkage.

[@mysticvalley2003]

I wonder if you can help me out? Periodically my boat starts hard warm or cold. Plugs gaped & timing correct. Engine ,coil & wires New , Carburetor rebuilt....when running its fine, plenty of power, ETC.....I'm thinking its the choke....I've adjusted it counter & clockwise one notch off from the center mark..your thoughts....thank you for your time and video!

[@barrybebenek8691]

Two questions: 1. If my mix screw is set at 1-1/2 out from seated, are you saying it can be turned out 3,4,5+ turns (from seated) and still not pop out of the carb? It will run with that many turns out? (I was nervous to turn more than 2 turns out). 2. Do I put in forward gear+idle, then remove the throttle cable at that point so the idle can be set? Or can the cable be left attached during that? Thanks.🇨🇦

[@brianhip3480]

I rebuilt my 2 barrel mercruiser carb it starts and runs good except there is alot of smoke and black residue coming from my exhaust do you have any suggestions on how to fix this problem? Does it mean im running to rich therefore adjust the fuel mixture screw on the carb? Thank you for any input....

[@jasonwilkerson3201]

Thanks for the great video. I'm rebuilding mine soon - one quick question - are you supposed to set the computer to base time by grounding the purple/white wire on the Thunderbolt V ignition so it doesnt mess with idle while setting the idle?

[@MadPropsMakes]

Nope, you set the idle in regular timing. However, you need to be IN the water in forward gear at operating temperature... I find my motor idles at around 900-1000rpm when on muffs out of the water when its correctly set.

[@jasonwilkerson3201]

@@MadPropsMakes well thanks for the fast response! That helps alot - have you ever noticed any difference between using different gas? Say 87 with ethanol and 93 without ethanol?

[@MadPropsMakes]

@@jasonwilkerson3201 No, not really... I've pretty much only ever used 87 pump gas... I've gotten ethenol free from a marina because thats all they had, but didn't notice any difference. Ethenol gas actually has a higher octane rating because the ethenol detonates at a higher temperature so you're less likely to knock, but you get worse MPG, or in a boats case, gallons per mile...

[@jasonwilkerson3201]

@@MadPropsMakes ok - thanks again!

[@tonygatto48]

i have a question.... my 3.0 runs perfect ... untill i ride it about 15 min.. then spitting and sputtering; I changed the points and condenser. I also emptied the tank and made sure to run non ethnol for a few time. Any ideas on proper trouble shooting methods as i dont like throwing parts at things... tks

[@3006whitelightnin]

Hey man, so I rebuilt the carb on my 5.0 mercruiser. Everything is running great with just one problem. I can't get to 5500 rpms for WOT. I get to about 4000 and that's as far as it will go. Is there something I need to adjust different to get about 1500 more rpms at WOT?

[@JKURR]

I don’t have that tab to bend for the fast idle arm at 8:54. I have a 96 Merc 3.0. Do you know if there are different variances depending on the year range?

[@jeremygarland6428]

I subbed great video. Question. I rebuilt the same carb. My boat idles fine on startup, accelerates fine but when I pull back the throttle to idle the engine idles super low and dies. Start engine back up idle is fine again. What would cause this?

[@MadPropsMakes]

Thanks for watching... not entirely sure... could be your idle is set too low... most mercs should idle around 650-800 rpm in the water and in gear.

[@MadPropsMakes]

@The Truth that's around the high end of the spec but sounds about right...

[@louispawlowich8869]

I suspect the choke is not set properly and is staying to far open.

[@kirkniles4184]

So....what does the hose barb on the back of the carb do

[@nicholasrodriguez8502]

Question. My newly rebuilt mercarb will start and idle for 30 seconds then die. If I restart it and bump up the RPMs, it dies within 10 seconds. New fuel filter. Any ideas?

[@kevceckim]

Same with me, I replaced the oil pressure switch the one next to oil pressure sender.

[@kubaSWAT]

Hey in 10:42 You are screwed in you idle cam screw 2 turns then closed choke, I have a problem, when screwed in I cannot move choke anymore... Can I ask you to make a video how does it work on a boat? Thanks

[@MadPropsMakes]

Yea, I plan to make a video at some point on how to do the adjustments on the water... Just haven't been doing much video/boat work lately since I splashed it and just enjoying it while the weather is still good lol

[@kubaSWAT]

Madprops Boatworks thanks I’ll appreciate it because I’m trying to fix that thing... btw. thanks for reply on my topic on iboats,

[@kubaSWAT]

Madprops Boatworks I mean if you can record how the cam/rods works. So I can compare and solve the issue why the choke is frozing when I screw in the idle screw

[@xander2204]

How do you use a vacuum gauge on that carb ???

[@alecbaldwinsnotpropgun]

Take the bolt out on top of the intake manifold and put gauge there

[@iselili2]

Love the video… hate the background music!!! 😅

[@TheRustbucketracing]

That music

[@davidmaiolo]

Good video, but my friend, get on with it. The long intros are not needed

[@ryanryan8923]

Uumm, ummm, ummm, uummm

[@flyfields2]

way to long winded, get to the point!

[@getitdone6694]

Maybe you should make a video and educate us on your astute sense of tutoring at High speed. Or better stay off the crack and enjoy this great video