!!??engine popping and sputtering??!!

5.7 merc 2bbl carb so im runnin fine all morning then at 4k rpm cruisin all of a sudden i hear a light backfire then once again so i back down on the rpm then as i head back the other direction it starts making all kinds of sputterin and poppin wouldnt even stay on plane then i had to cruise back at about 2k rpm it ran smooth up to 2k any more than that it felt like i was hittin a rev limiter. then i shut the boat off and it wouldnt start back for a few min......... brand new rebuilt carb. new fuel filters and pump....... any
help would be greatly appreciated

Re: !!??engine popping and sputtering??!!

Mine did the same thing. I thought putting a 4bbl on and intake swap would fix it. Nope. If you are mechanically inclined, just for satisfaction of knowing, do a compression check. They rent comression gauges at autozone/oreilly's if you don't have one. Write down each reading. If one is way off, you may have a burnt valve.(I had 4 burnt valves). That is worst case scenerio. Check you igniton system(plugs, wires, cap, rotor.) Mine were the original from 1997. If none of those are the problem, There is a diagram that some nice people put up here to test your fuel system. (stuck anti siphon valve, collapsing fuel line, bad fuel pump, etc). Also, check all electrical connections. Did you buy your rebuilt carb, or did you have your's rebuilt? I bought a Ebay rebuilt 4 bbl to replace my 2bbl, and it was junk. After buying a brand new carb, Full tune up, and having my heads rebuilt, mine runs good. Hopefully you will not need nearly as much. Best of luck. If I can help, Please, let me know. There are some great people on here that helped me, and will help you get it figured out.

Re: !!??engine popping and sputtering??!!

brand new rebuilt carb. new fuel filters and pump.......

Click to expand...

Ayuh,.... Sounds like Water in the fuel, or just plain ole Bad gas...

Re: !!??engine popping and sputtering??!!

I know, I keep pushing the coil theroy. Well that because I've had 2 of them go bad.

Re: !!??engine popping and sputtering??!!

Need more info as others would say. Year of boat Ect.

Re: !!??engine popping and sputtering??!!

i changed the coil today with an accell supercoil and ran it on hose pipe idles good revs good until i hit about 4k then it popped so i let it idle and reved it around 25 to 3 back and forth no prob so i rev it wot again and starts poppin and cuttin out from 35 and up then i tried it again only easing into throttle no popping but around 4k it was almost like it was hittin a rev limiter

the boat is a 97 rinker captiva 212 cuddy 5.7 merc and i dont know why they put a 2bbl on it but they did

Re: !!??engine popping and sputtering??!!

did you empty the fuel tank and try fresh gas? or better yet, just run it off a small gascan to see if that cures the problem? sounds like water in the fuel / bad gas to me...

Re: !!??engine popping and sputtering??!!

checked compression 150 psi on 123456 and 140 on 7 8 tryed advancing timing on distributor same crap checked cap button everything firing clean and even inside guess tomorrow i will try puttin new plugs in it and runnin of a gas can w fresh gas

Re: !!??engine popping and sputtering??!!

Great to hear compression is good on all cylinders. You said you put on a rebuilt carb. Did you buy one, or rebuild yours? I purchased a carb from a Ebay company that sells the 2 barrel carb, and the 4 barrel. My"rebuilt carb" was not even close to right. I now have it as my second anchor for the boat, cause that is what it is good for. Also, carb gasket is good? Carb is tight, and not sucking air at the base? Just a thought. Also, if you have any question about your carb, let me know. I have a 2bbl from the same year boat, and I could let you borrow it to try out if needed. Let me know!

Re: !!??engine popping and sputtering??!!

i rebuilt it twice !! the first time a buddy that works at a boat shop did it and after sittin all winter the float needle was stickin and not letting fuel in so i pulled it apart and rebuilt again w all fresh parts soaked it and the whole nine yards new accel pump, float needle, jets, power valve ..... float is set perfect all new gaskets although we did tear a gasket cus the damn float was still floodin so we were on water and had to quickly pull carb apart and bend float where it would close all the way i guess maybe the electronic fuel pump was pushin harder than manual pump... but i dont know if that would have any effect because its over torn over by the bowl and it would be leaking if wasnt sealed.. im starting to think maybe its just the bad gas mixed w new gas when i took it out 2 weeks ago it ran fine as soon as i put it in water for the 10 min it took to get to cove then it ran good after it sat for 45 min and we went 10 min to a marina w no problems then after 30 min we headed to another marina and within 5 min of cruisin 4k rpm it started to pop here and there then i stopped and sat for a few min and when i headed back down river at about 4k it started poppin more often then started sputterin out and fell off plane then wouldnt rev over 2 to 25rpmbut it ran smooth at 2k all the way back to dock then as i waited to dock i shut it off and it wouldnt start back for about 10 to 15 min>>??

Re: !!??engine popping and sputtering??!!

thanks for the offer but i live in tennessee 30 min from nashville think i might put this 4bbl edelbrock marine carb on it ive been puttin it off cus i dont feel like messin w intake but i think im going to have to if the gas can thing doesnt work

Re: !!??engine popping and sputtering??!!

Ok. Glad to hear you used your old carb to rebuild. One other thing I have heard of, have you run the blower motor the whole time you are out? I have heard of engine compartment's that get to hot, and caused problems. One person on here had the ign. module going bad, and if he ran the blower motor, it would run good. I think you are on the right track with the fuel. Did you pour the fuel from the water/fuel seperator, into a see thru container and look at it? I know how you feel chasing down problems, when all you want to do is sit out, and enjoy. You will get it figured out! When you do, be sure to let all of us know!

Re: !!??engine popping and sputtering??!!

Just did the same swap on the intake and carb. I found a merc intake for free, and the flame arrestor. Swap goes pretty easy really. If you do the swap, things you will need,
Throttle cable bracket(this holds your circuit breaker also)
New metal fuel line(if you have mech. pump, a new 90 fitting out of the pump)
Flame arrestor(one that will fit the 4bbl carb)
Intake Manifold
Carb(I just bought a 1409 Edelbrock. Love it)
Intake gaskets

I marked the body of the distributor and the mount with a scratch, and then scratched the rotor and the pickup inside the dist. That way I was really close on timing.

Also, I have found mercruiserparts.com is great to look up the parts you need, and saves time if you order at the dealer. Best of luck!

Re: !!??engine popping and sputtering??!!

ok ran it on gas can today and nothing has changed still acting up

Re: !!??engine popping and sputtering??!!

Just a question? How did the cam and lifters look when you changed the intake.

Re: !!??engine popping and sputtering??!!

mine did the same thing, bought the boat from a guy that had it in a marina outside Murfreesboro, TN after all the floods. He put fuel in it from that marina and it wouldn't hardly run. Itook the fuel filter/separator off and dumped it out in a glass jar. The fuel settled and I found a lot of sand in the fuel. I then changed the filter and put new gas in, no problems since.

Re: !!??engine popping and sputtering??!!

I checked my fuel water sep filter about 5 times replacing it 3 times because there was some debris in it.


Then one time after running like crap I checked the filter once again and it was 80% full of water.

Had to pump 30 gallons of fuel out and put new in.


so just because there is nothing in the filter now doesn't mean there isn't anything in the tank.

Re: !!??engine popping and sputtering??!!

i pumped almost 10 gallons of gas out of it and it was clean no water no trash i even ran it on a new gas can with fresh gas.. i just posted a new thread it turns out i pulled the icm off the back of distributor and it had water in it!!! so i shook some of it out and then put the icm in a bag of rice hoping to pull the water out of it well c what happens

Re: !!??engine popping and sputtering??!!

Points ignition? Real cheap to replace the condenser and check the points.

Re: !!??engine popping and sputtering??!!

It's an ignition problem. Weak Valve springs will also act like a rev limiter when the valves float, but the engine will always run normally at lower rpms.