2007 3.0L 135HP Merc question

[Runwithem513]

ok a little guidence from some of you all please.

so i took the boat out for its first run of the year a few weeks ago and had some problems.
while the engine is idleing the RPMs jump up and down eraticlly and the engine has a tendency to stale on me.
if running at anything above 2000 rpms it runs like a top. so my question for you guys is 1. what do you think may be causing this, and 2. where do you think i should start as far as diagnosis.

boat was not winterized, "Florida winters" but all water was drained and fuel stabillizer was used.

Thanks,

Kenneth

 

[MarkSee]

Re: 2007 3.0L 135HP Merc question

Welcome to IBOATS.

Have a water separating fuel filter installed? Another type of fuel filter?
When was the last time it was replaced?

Have fresh gas in there?

It might be something else but maybe something is causing some fuel starvation at low rpm.

Mark

 

[Runwithem513]

Re: 2007 3.0L 135HP Merc question

Thanks for the reply.

This boat did not come with a water seperating filter. i changed plug wires already and checked for spark in each. i also siphoned out all old gas and put new gas in her and the same thing occurs.

kenneth

 

[elkhunter338]

Re: 2007 3.0L 135HP Merc question

I would put a piece of clear line on the fuel line at the carb and make sure no air bubbles are present.
I had similar problem with small outboard and it was a cracked fuel pickup tube.
ran fine wot, but stall run rough at idle.
Check fuel pressure. Could be carb issues piece of something in the idle system.

 

[Runwithem513]

Re: 2007 3.0L 135HP Merc question

so put the clear line coming from the fuel pump to the carb correct?

and i was planing on doing a fuel pressure check and a timming check.

i just hope its more of a carb problem then an internal engine problem, it also boogs down and dies everynow and then when i go to give it a little more juice, sound like a carb problem?

im currently waiting on family to ship my compression kit from ohio so i havent been able to check compression yet.

 

[Bondo]

Re: 2007 3.0L 135HP Merc question

so put the clear line coming from the fuel pump to the carb correct?

and i was planing on doing a fuel pressure check and a timming check.

i just hope its more of a carb problem then an internal engine problem, it also boogs down and dies everynow and then when i go to give it a little more juice, sound like a carb problem?

im currently waiting on family to ship my compression kit from ohio so i havent been able to check compression yet.

Ayuh,... Welcome Aboard,.... Sounds like the carb needs Rebuildin'...

 

[Don S]

Re: 2007 3.0L 135HP Merc question

so put the clear line coming from the fuel pump to the carb correct?

and i was planing on doing a fuel pressure check and a timming check.

No, you don't put a clear hose on the pressure side to check for air, that is done by putting a piece of clear line on the suction side of the fuel pump and see if air is getting to the pump. |
If there was a leak on the pressure side, it would be a fuel leak, not air getting into the system.

The 3.0L engines never come with a water separating fuel filter, but they should, and you should install one.

Have you checked the fuel filter in the pump? There is also a strainer in the inlet of the carb. If you had to clean the tank, no doubt there is garbage in the filters.

 

[Runwithem513]

Re: 2007 3.0L 135HP Merc question

Hey thanks for the info I didn't really think that one through
As far as the line goes "night shift sleepy post" I have not gotten into the
Filters yet but will when I one day might see a day off lol. I was
Wandering though, could a bad anti siphon valve on the gas tank possibly
Cause some of these symptoms? I noticed whole filling her up
The other day that when I pumped the gas like I normally did
Last year it was like it was hitting a dirty screen or something and coming back out,
But a slower fill up was goin in just fine.

Thanks for the replies,

Kenneth

 

[Bondo]

Re: 2007 3.0L 135HP Merc question

Hey thanks for the info I didn't really think that one through
As far as the line goes "night shift sleepy post" I have not gotten into the
Filters yet but will when I one day might see a day off lol. I was
Wandering though, could a bad anti siphon valve on the gas tank possibly
Cause some of these symptoms? I noticed whole filling her up
The other day that when I pumped the gas like I normally did
Last year it was like it was hitting a dirty screen or something and coming back out,
But a slower fill up was goin in just fine.

Thanks for the replies,

Kenneth

Ayuh,.... Sounds more like a plugged Vent line than the anti-siphon....

 

[Don S]

Re: 2007 3.0L 135HP Merc question

Wandering though, could a bad anti siphon valve on the gas tank possibly
Cause some of these symptoms? I noticed whole filling her up
The other day that when I pumped the gas like I normally did
Last year it was like it was hitting a dirty screen or something and coming back out,
But a slower fill up was goin in just fine.

Your description is not an anti-siphon valve, sounds more like a plugged fuel tank vent. and yes a plugged tank vent can cause running problems.

An easy test is to run the boat, when it slows down, remove the gas cap and see if it picks back up.

Mud dauber wasps seem to like to build nests and block tank vents. They must like the smell of gas.

 

[Runwithem513]

Re: 2007 3.0L 135HP Merc question

Aha getting my hopes up now but I think Ima start their. Now I did hear a kind of squeaking, hissing noise and tried the old carb cleaner
Trick with no success it sounded like it was coming from the carb/down to the alternator area, maybe I was mistaken and it came from the gas tank area which is located right next to it. Possibility it woul make this noise?