warm starting issues merc 5.7

[dgopetactical]

Hello,
the last couple of times I have been out i noticed when i turn the engine off for 5 + minutes on the water and try to restart it cranks and wont start (maybe a sputter or 2). If I give it 1/2 throtle it will start in about 10 seconds with a few sputters within thoes 10 seconds before it fires up. I have no other issues with it and it seems to run great other than this issue. During cold start (sitting a week or so) i pump the throttle a few times and it fires up alot quicker than when the engine is warm (4 cranks).
In the beging of the season it was just a turn of the key on a warm engine and it would fire, now it has slowly progressed into this

I have a holley 4bbl 2 years old electronic choke
fuel pump replaced in June.....6.5 psi on holley inline pressure gauge (when running)
plug wires/cap replaced 2 seasons ago
fuel filter/seperator replaced in june
spark plugs replaced in may...
If somebody could please give me a starting point to try to solve this issue that would be great.
Thanks,
Denny

 

[dgopetactical]

Re: warm starting issues merc 5.7

bump

 

[hoverman]

Re: warm starting issues merc 5.7

i have a 91 merc 5.7 and noticed it just has a paper gasket between the carb and manifold which will allow heat to get to the carb could cause alot of problems

 

[Bondo]

Re: warm starting issues merc 5.7

I have a holley 4bbl 2 years old electronic choke

Ayuh,... It sounds like a Carb problem,...
You need a Holley guy, that's Not standard issue on that motor,...
Merc hasn't used a Holley in atleast 20 Years, if they ever did...

 

[JustJason]

Re: warm starting issues merc 5.7

Easy enough. Sounds like its flooding out on shut down. Pull of the flame arrestor and give the boat a hard run. Shut it down and run back to the motor (or just have 2 people) and look down the venturi, it bet its dumping fuel.

 

[dgopetactical]

Re: warm starting issues merc 5.7

Ayuh,... It sounds like a Carb problem,...
You need a Holley guy, that's Not standard issue on that motor,...
Merc hasn't used a Holley in atleast 20 Years, if they ever did...

When I bought the boat 4 years ago it had a holley 4160 auto carb on it and a holley intake. I then switched to a new holley marine 4bbl 2 seasons ago.
Denny

 

[dgopetactical]

Re: warm starting issues merc 5.7

Easy enough. Sounds like its flooding out on shut down. Pull of the flame arrestor and give the boat a hard run. Shut it down and run back to the motor (or just have 2 people) and look down the venturi, it bet its dumping fuel.

If I find out this weekend it is dumping fuel what is the remidy to fix it. I can almost say for sure it started when I put a new marine fuel pump in (almost). The old one was putting out 3.5 psi and holding me back on my WOT. Now with the new one I get 6.5-7 psi got my WOT back and performs better than ever but now have a warm starting issue.

I am far from a carb guy but the only adjusment on this carb are the 2 needle screws. Everthing else is factory set and sealed according to the paperwork. I could be wrong about getting tunnel vision toward the new fuel pump but that is the only upgrade i made in 2 seasons. is the psi now too high??
Thanks,
Denny

 

[Bondo]

Re: warm starting issues merc 5.7

If I find out this weekend it is dumping fuel what is the remidy to fix it. I am far from a carb guy but the only adjusment on this carb are the 2 needle screws. Everthing else is factory set and sealed according to the paperwork.

Ayuh,.... The Remedy to Fix it is,... Rebuild the Carb...

A good quality Carb Kit should have instructions,+ settings listed...

 

[dgopetactical]

Re: warm starting issues merc 5.7

Ayuh,.... The Remedy to Fix it is,... Rebuild the Carb...

A good quality Carb Kit should have instructions,+ settings listed...

ok, will do...that will be my winter prodject...I just find it weird i only have 33 hours on this carb and its 1 1/2 yr old. but then again I have seen stranger things happen.
thanks
Denny

 

[Razvanbuc]

Re: warm starting issues merc 5.7

I have a similar issue. The carb was getting flooded when off/warm and engine was starting very hard about 4 5 cranks. The carb is at the mechanic now to rebuilt.

 

[bruceb58]

Re: warm starting issues merc 5.7

Just to make sure...you are not pumping the throttle at all before starting correct?

 

[dgopetactical]

Re: warm starting issues merc 5.7

Just to make sure...you are not pumping the throttle at all before starting correct?

I only pump the throttle on cold starts.....when it dont start "warm start" I evantaily have to give it 1/2 to 3/4 throttle to get it started .
Denny

 

[dgopetactical]

Re: warm starting issues merc 5.7

I was getting the boat ready for our weekend trip to the chesapeake bay, I took the flame arrestor off to clean it and I noticed when i lifted the arrester I heard a click and the choke went shut.....

I came to the conclusion that the choke was not shutting all the way all the time and the choke "arm" was hanging up on the arrester. I made a cork gasket ring spacer and put it under the arrester to raise it 1/4" and adjusted the choke. It did not have any issues afer that + it fired right up cold or warm/hot. The real test will be this weekend.
thanks for all the help,
Denny

 

[gene8084]

Re: warm starting issues merc 5.7

You didn't say whether you had a good spark / dull yellow.

I had a similar problem at one point that turned out to be a tired coil that wasn't generating a white/blue spark when the engine was hot.​

 

[dgopetactical]

Re: warm starting issues merc 5.7

You didn't say whether you had a good spark / dull yellow.

I had a similar problem at one point that turned out to be a tired coil that wasn't generating a white/blue spark when the engine was hot.​

Im pretty sure my problem was the choke issue. Thanks for the tip. my coil is old, just gotta figure out how to test it.
Denny

 

[Maclin]

Re: warm starting issues merc 5.7

deleted

 

[Maclin]

Re: warm starting issues merc 5.7

Sorry, I had posted something then reread all of this and realized DG had found a mechanical linkage interference problem and my advice was not relevent.

 

[myoldboat2]

Re: warm starting issues merc 5.7

Easy enough. Sounds like its flooding out on shut down. Pull of the flame arrestor and give the boat a hard run. Shut it down and run back to the motor (or just have 2 people) and look down the venturi, it bet its dumping fuel.

JustJason, please read my thread:
http://forums.iboats.com/showthread.php?t=351404

I'm interested if you think I'm having that problem. Hope to check the carb tomorrow. Thanks.

 

[myoldboat2]

Re: warm starting issues merc 5.7

dgopetactical, in case your carb is still dumping fuel at shutdown, the reason mine was dumping fuel was that the carb float was leaking and had some gas in it, so it was heavy and wouldn't close the needle valve.

 

[dgopetactical]

Re: warm starting issues merc 5.7

thanks for the information, Im sure it was the choke hanging up on the flame arrester, I have had the boat out 4 times since i raised the arrester and the problem never happened again.
thanks,
DENNY