Limited Power on Mercruiser 3.0LX Alpha

[NobullFL1]

Hi, been lurking on these forums and finding great info...Thanks to all who help! I have a SeaRay175 with the subject engine. About 1 month again, I started to notice some poor performance. First, it started with a rough idle when warm, then some hesitation when I gave it throttle to now running at ~60 power with WOT? I have replaced all filters along the fuel line (water separator, fuel pump, carb intake) and did a rebuild on the carb. It's idling great and responding to throttle but still limited power at WOT? I did check the distributor, just made sure contacts were clean, etc. Not sure what to do next? Timing? Looking for some suggestions?

 

[alldodge]

Howdy
With low on power do check timing
Also do a compression test. The how to is in the stickys

 

[NobullFL1]

So frustrating! Compression checked-out solid...145 on each cylinder. Checked the timing, reset base to 1degree BTDC, EST traveled to ~10degree BTDC.
Still no RPM's or Speed at WOT....it's topping out ~3500 RPM's. Get's here at ~60% throttle, then no more. Everything else is running fine.

Not sure where to from here?

 

[alldodge]

Being an LX it would have a carb (2 or 4bbl). Could use a serial number so we know the configuration

Need to check fuel pressure, should be 3 to 7 psi from idle to WOT
Check the fuel tank antisiphon valve

Your not getting timing advance or not enough fuel
Have you heard any backfiring ?
Is the fuel filter staying full?
What did the spark plugs look like, all the same?

 

[NobullFL1]

The serial on the Carb is 05924A-1. 2bbl.
I'll check the fuel pressure and fuel tank antisiphon valve. I didn't do this previously...just ran down the fuel line and replaced the filters.

 

[NobullFL1]

BTW - No backfiring. When you say "fuel filter stating full", are your referring to the fuel pump? The plugs were a bit messy (carbon/wet) but I attribute this to all of the adjustments I made after the carb rebuild? I cleaned them up and will take another look.

 

[alldodge]

If it would backfire at higher rpms then this would mean its running out of fuel. With it not doing that then this would not be the issue. If the filter was staying full then the pump could be weak or there would be a restriction.

If plugs are still carbon and/or wet then the carb needs some work in adjusting it. If its wet then the carb is flooding the motor.

I was wanting the motor serial number

 

[Scott Danforth]

first, what year do you have?
second, not sure of any 3.0 liter with a 10 degree BTDC timing.

the older points were 4-6 degrees BTDC
EST was -1

 

[alldodge]

reset base to 1degree BTDC, EST traveled to ~10degree BTDC.

Set at 1 BTDC

 

[NobullFL1]

The engine serial is 0F748305

 

[NobullFL1]

1 BTDC is base timing for the EST. Once the 12v is is removed the EST will time around 10 BTDC at idle.

 

[alldodge]

Thanks for the sn, I'll be waiting for the plug read

 

[NobullFL1]

FYI.....

 

[Scott Danforth]

how old is your fuel?

 

[NobullFL1]

So ran it out at WOT for several minutes, brought it in, checked plugs and they are clean and dry? I am not able to check the fuel pressure, I don't have the carb adapter for testing.

 

[NobullFL1]

Fuel is fresh...I load about 10gal a month pretty consistently.

 

[NobullFL1]

checked the anti-siphon valve...looked good. Bal and spring were moving freely, no residue or debris.

 

[alldodge]

Need to see if your timing is advancing and how far. Should get full advance above 2500 but at least 3000 rpm

 

[NobullFL1]

Howdy
With low on power do check timing
Also do a compression test. The how to is in the stickys

Either the links in the sticky's are bad or I'm dong something wrong? Can you verify?

 

[alldodge]

Do agree, the Stickys are messed up
Best to do warm but cold will also work. If you find a cylinder lower then the others then would need to warm motor up to verify it doesn't change

Remove all plugs, open throttle wide open. Unplug the connectors from the coil, or pull the kill switch.
Connect gauge to a cylinder and crank motor at least 4 revolutions, record reading. Go to next cylinder and repeat