96' Merc 150hp EFI Smokes and surges when throttling up under load

[LakeRat85]

I have been working on my 96' 150 horsepower EFI Mercury. I just received this boat as a hand-me-down from my father. The boat ran fine when it was parked 2 years ago. I took it on the lake last weekend and it idled rough, would try to die when putting under load, and could not reach plane with motor bogging and surging. I have pumped out the old gas in the entire system from tank to injectors, change water fuel separator (old one did have water in gas and particulates), removed and cleaned all 6 injectors and manifold, checked VST for debrie, damage, and cleared all hose connections then installed new o-ring gasket on VST housing, checked low and high pressure fuel pumps, changed spark plugs, wires, and checked for spark, changed thermostats while I was there, checked compression and port side cylinders were all 112 psi and starboard side cylinders were 120 psi. Atleast now it idles without trying to die, but smokes mainly white/gray with sometimes blue hue smoke. When throttling up in neutral it still seems to run rough. I have a detonation module coming in the mail, but that is a stab in the dark. Any help would be greatly appreciated!!

 

[LakeRat85]

I have been working on my 96' 150 horsepower EFI Mercury. I just received this boat as a hand-me-down from my father. The boat ran fine when it was parked 2 years ago. I took it on the lake last weekend and it idled rough, would try to die when putting under load, and could not reach plane with motor bogging and surging. I have pumped out the old gas in the entire system from tank to injectors, change water fuel separator (old one did have water in gas and particulates), removed and cleaned all 6 injectors and manifold, checked VST for debrie, damage, and cleared all hose connections then installed new o-ring gasket on VST housing, checked low and high pressure fuel pumps, changed spark plugs, wires, and checked for spark, changed thermostats while I was there, checked compression and port side cylinders were all 112 psi and starboard side cylinders were 120 psi. Atleast now it idles without trying to die, but smokes mainly white/gray with sometimes blue hue smoke. When throttling up in neutral it still seems to run rough. I have a detonation module coming in the mail, but that is a stab in the dark. Any help would be greatly appreciated!!

This is a picture of what the fuel looks like in the VST after doing everything above and testing the work done. It looks dark to me...... but I do not claim to know what it should look like. Also my motor serial# 0G423221. Thanks!

 

[Dukedog]

may need ta send injectors out for a good cleaning... new o-rings..........

 

[LakeRat85]

I pulled the injectors and did a total clean out job. Pulled injectors, fuel rail, and the micro screens at inlet of injectors, soaked and cleaned them. Pulled and checked o-rings set aside. Then used a 2 foot long 3/8" hose with hose clamps and inserted base of injectors into one end then hose clamped, filled hose with chemtool b-12, put air gun into other end of hose with hose clamp and put 65 psi on the line. Put power to injector and tapped ground to energize it. 3 were partially gummed, but cleared by 3rd tap of battery. They all misted equally. Then cleaned fuel rail and manifold housing, cleaned and checked gaskets and hose connections and then put back together. Boat now will idle and not try to die, but still smokes a ton and does not like to be put under load. Pulled brand new plugs and they are all partially wet with black oil residue..... I'm starting to wonder if there is to much oil in the gas? I have read that the check valve under the starter is notorious for going bad and messing with pressures to reservoirs, so maybe head that direction.....

 

[Dukedog]

too much oil doesn't usually effect tha run part.. it jus smokes a little more.. we ran 24 ta 1 in our hot rods with no problems other than a little "smokey" at idle..... black/wet sounds like they are losin' fire for whatever reason....

 

[Faztbullet]

Need to send injectors off to Brucato to have cleaned,flow tested and balanced.

 

[LakeRat85]

So today I was able to put a fuel pressure test kit on it. Was 35 psi at idle and dropped to 34 psi on throttling up. 1 min after shutting off motor psi was 34, five min was 32 psi and 15 and 30 minutes were 31 psi. Storms moved in so did not get to see an hour psi. While putting top cowling on I noticed that the linkage that controls the oil flow to vst was stuck wide open being pinched between the vst and the feeder house from the top oil resivore. Adjusted the linkage, control arm, and turned the bolted hose fitting connection a 1/4 turn and now when going through the throttle positions it does not stick wide open. So hopefully that will help with the smoke. Did not get to test the theory as storms moved in and shut me down......