2004 150HP EFI Problems

[jacobk]

2004 Mercury 150HP EFI
Serial Number: 0T962231
250hrs
Strictly using Mercury 1-2-3 and Mercury premium plus.

Things I’ve tried/checked:
120 PSI compression across the board
Has spark in all 6 cylinders
New Spark Plugs (NGK BPZ8HS-10)

Yesterday morning at the ramp it ran fine but I noticed noticed it putting out 11v at WOT. After running around the lake, I had a long idle through a no wake zone it wouldn’t go past 2,000 RPM and started to misfire at idle.

We have our club classic Saturday, any help would be appreciated. For now the plan is to just troll everywhere if I can’t get the Merc back up. 😢

[JOE54]

ohm test fuse link /big red wire on alt and all other fuses on mtr check um,and belt

[jacobk]

ohm test fuse link /big red wire on alt and all other fuses on mtr check um,and belt

Tested that wire and the 100 amp fuse was blown, just replaced it and will be winging it tomorrow.

[jacobk]

Putting out 14v now but still running rough & not getting past 2,000 RPM.

[EuropeanAM]

Check the spark plugs to make sure you didn't foul them trying to run around at low RPM's and voltage.

[jacobk]

Check the spark plugs to make sure you didn't foul them trying to run around at low RPM's and voltage.

Will swap out with another fresh set and run it again sometime this week, will update post with results.

[jacobk]

120484648_3549898058388496_4905548475599076652_n.jpg1.jpg

Pulled the plugs tonight and put in a brand new set. Will be running the boat tomorrow after work.

[JOE54]

waaaaaaaay to rich got somethin wrong

[EuropeanAM]

+1... I would also be checking the fuel pressure (relatively common to find it HIGH... often caused by debris under the regulator or debris on the regulator screen).

[jacobk]

Roger that, will hold off on running it until I check the regulator out.

[jacobk]

Alright, revisiting this thread as I ended up just storing the boat early last season.

Fuel pressure at idle was 39psi, VST and regulator screens were pretty clean, MAP sensor was also cleaned.

Put in a fresh set of plugs before hitting the lake, boat started fine as usual. Had to idle for about 10 minutes to get out of the no wake zone, it bogged a little bit before getting on plane.

Water temp was in the high 40's and I was seeing 145-150 F at idle and 80 F at WOT on the SmartCraft gauge.

[jacobk]

175533823_486597219446911_2823151953973263342_n.jpg
Just pulled the plugs and left bank (2,4,6) looks to be running very rich compared to right (1,3,5).

This is after running around the lake all day then doing the same 10min idle back to the ramp.

[aussiejake]

By the look of the plugs the left bank appears to be running a bit cold on idle.
Maybe check the thermostats, might find the left bank is stuck open with debris, but then 150 F on idle is around the mark for the thermostats opening. I would expect higher though when going through the no wake zone on less than 1200- 1500 rpm before the poppet starts to come into play.

Would be interesting what the plugs looked like before going through the no wake zone.

When my exhaust tuner had fallen off the left bank (2,4,6) always ran rich and fouled plugs....not sure why that bank but the right bank never had the same problem.

[JOE54]

^^^^^^^ agree need to verify temp of each side of mtr

[jacobk]

Won’t be able to get on the water until next weekend, forecast is looking awful & we just got snowed on. Appreciate the insight, will report back ASAP.

[leonreno]

If the boat is there with you, you can pull thermostats and inspect for debris before you go, pretty easy to check thermostats. Best way to check temp is to use a IR thermometer and measure on the block side of the thermostat housing on each side.

[jacobk]

If the boat is there with you, you can pull thermostats and inspect for debris before you go, pretty easy to check thermostats. Best way to check temp is to use a IR thermometer and measure on the block side of the thermostat housing on each side.

Good idea, Yes the boat is in a heated garage. I’ll pull the left thermostat this week since the weathers not looking great.

[jacobk]

Just pulled the thermostat from the left bank, a little bit of gunk but it doesn't look horrible. Going to clean it up and test functionality tonight.
thermostat 1.jpg
thermostat2.jpg
thermostat3.jpg
thermostat 4.jpg

[jacobk]

Tested with some hot water, thermostat opens & shuts just fine. Cleaned up and reinstalled.

[EuropeanAM]

See how it does. On a side note- it's probably time to replace those T-stats, anyway.