5.0 Mercruiser, turn but won't start.

[FairWinds & FollowingSeas]

01 mercruiser 5.0 serial #M015594
Points distributor
2 barrel Rochester Carb


So during my last trip out, we launched the bat and chugged along for about 25 min before we were about out of the no wake channel and the boat started to sound rough and died. When i tried to start it again it would not start. so i increased the idle speed screw a little and it fired back up. But when ever i would give it throttle it would struggle and back fire smoke into the carb and die. I could get it to start up again but even that wasn't easy. So as sea-tow is bringing us in my father in law takes the top of the carb off, it appeared like there wasn't a lot of fuel in the reservoir so i figured to was a fuel delivery problem.
When i got it home i noticed when the key was turned the fuel pump wasn't coming on, so i jumped the three pronged oil pressure switch, so now the fuel pump turns on and STAYS ON when the key is turned to on which works for now i guess. so i got a new gasket and put the carb back together but in the process ripped the rubber gasket the goes around the accelerator pump. I put it together anyway knowing that it wouldn't be needed just to get the engine started.

Now when i go to start it the motor turns but will not start. I checked to see if it was getting spark from the distributor and it is, i poured gas down the carb and opened the throttle and it sounds like it wants to start but it won't. so other then a compression test i don't know what to do.

Thanks.
:facepalm:
P.S. the carb has been rebuilt four times in the last 10 months, so its pretty clean.

 

[chimmike]

Re: 5.0 Mercruiser, turn but won't start.

sounds like a fuel delivery issue, and I'd replace that gasket. May be causing a vacuum or air issue?

 

[Don S]

Re: 5.0 Mercruiser, turn but won't start.

01 mercruiser 5.0 serial #M015594
Points distributor
2 barrel Rochester Carb

You might want to do some checking, you shouldn't have a Rochester carb, and Merc hasn't used a points distributor on a V8 for 30 years.

And rebuilding a carb 4 times doesn't mean it's going to work. Sometimes they are just plain junk.

Have you actually just let it warm up before trying to give it throttle?

 

[FairWinds & FollowingSeas]

Re: 5.0 Mercruiser, turn but won't start.

I cant get the thing to start up, so therefore i cant get it warmed up. I just got back from the parts store with another Rochester carb rebuild kit to replace the accelerator pump so THAT im sure of, the distributor, not so much... As for the carb being junk, i would hope that one of the three different professionals that rebuilt it would have said something about it being crap, and the boat worked awesome less then a month ago.

 

[Don S]

Re: 5.0 Mercruiser, turn but won't start.

Well, if you are trying to put a Rochester carb kit in a Mercarb, it's no wonder it doesn't work. Are you buying a kit by carb number or just asking for a kit for a Rochester 2 bbl?

How many idle mixture screws are in the carb.

You need to post some pictures of what you have, because what you say and your serial number have nothing in common.

 

[FairWinds & FollowingSeas]

Re: 5.0 Mercruiser, turn but won't start.

Its dark outside and raining now. Ill take some pictures and post what I find after work tomorrow.
Thanks for your quick response so far.