Running richrough Merc 57L

"My engine seems to be running

"My engine seems to be running rough. Plugs are wet with gas. Run engine at 2000RPM smell gas like a flooded engine does. New plugs, wires, gas/water separator. Had replaced a headgasket and had distributor out, roughly timed with a timing light. It has a Thunderbolt V ignition. Is it possible I have not timed it right and it is running really rich? Underpower it will only run about 2200 RPM full throttle, in neutral will run faster but sounds rough."

Carb or EFI?

Jeff

Carb or EFI?

Jeff

It is a 2BBL carb.

It is a 2BBL carb.

is engine warming up?do you se

is engine warming up?do you see any water in oil?is choke opening? when you sut off can you see gas dummping into carb. what is your compression? did you winterize?

"Engine starts fine. idles a l

"Engine starts fine. idles a little rough, in neutral will rev up but rough, under power RPMs won't go more than 2200, and very rough and smell gasoline not rotten eggs. see some signs of gas out of exhaust. was in water all winter, ran weekly. have not checked choke. added stabilizer. added PR-G to refresh gas. think all plugs firing, but plugs wet with gas not oil. did time by hand. read i should ground some lead to an ignition module to time. trying to narrow down problem and attack likely causes one at a time."

"Have you checked for spark on

"Have you checked for spark on all cylinders? Have you ever changed the plug wires? They're good for about 3 years of heavy use. After that, it's a coin toss. What about the cap and rotor?"

"Sorry, I should have read the

"Sorry, I should have read the original post more closely re: plug wires.

To add a few things, how long have you had this boat and how much regular maintenance has been done on it in its life? Have you taken a fuel sample and looked it? If it's old gas, don't expect any additives to bring that back to life. Is there water getting into the carb? Have you ever cleaned the flame arrestor? Has it ever been frozen in winter? How about overheated? Why was the head gasket changed? Are you sure the firing order is correct? Did you do a compression test before/after changing the head gasket?

If the timing is far off, don't expect it to run right. Is it possible to have the timing off? Sure it is. The only way to make sure is to time it the right way and not guess. Make sure you time it at the spec on the flame arrestor cover. If you don't have the specs, set it at 6 degrees BTDC. Make sure you have the right plugs ad they're gapped correctly. Vortec heads use AC MR43LTS plugs. Non-Vortec uses MR43T or TS. That will be on the flame arrestor cover too, along with the gap.

You may also have a leaky needle valve or leaking (and gas logged) float. If this is the case, you need to rebuild the carb, or have it done."

"Bought boat 2/2005. Little us

"Bought boat 2/2005. Little used. Overheated in the summer and froze up. I thought the enging siezed. referred to old time mechanic in TN on Old Hickory. He pulled engine said one bank cylinders had water in them. Said head gasket looked fine, said tested head. Repaired and returned it. ran about a week and siezed again. he was a drunk so diagnosed myself. water in cylinders. pulled head, bad gasket, he did not torque bolts correct, one loose. found other things he did wrong. I had head checked and milled, it was warped. reassembled. new plugs, wires, thermostat. ran and timed best we could. kept in water during winter, no freeze, ran weekly tied up. was running rough smoked a little, was thinking bad gas. runs pretty good in neutral, past 3000rpm. under way starts running rought 1800-2000rpm full throttle won't go past 2200rpm. Smell gas then also. Choke is not stuck. timed again today by the book. will take out tomorrow. One thing the timing mark tab only had a notch for TDC no other marks, so it is hard to see where it is at. It is a LH rotation engine, perhaps I have timing a little misadjusted?"

"If you use a timing light wit

"If you use a timing light with the adjuster on it, you can set that for +6 BTDC and then you just get the mark and the notch to line up. If it's advanced too far, it'll be really hard to crank over. If it's rotating counter-clockwise when you look at the front of the motor, advancing the timing will make the timing mark go in the same direction as the rotation. A rough setting for the timing is max RPM at idle, assuming the carb is setup correctly. Speaking of the carb, that may need setup, too. All of the other tests should be done, though. You want to make sure everythhing is set correctly before getting into the carb.

If the water went into the cylinder(s) at high RPM, it's possible to bend a rod. I would do a compression test ASAP and if you can, do a vacuum test, too. The vacuum test is a good indicator of the engine's health and takes place below the throttle plate, using a vacuum line. If it's low at idle, it has problems.

Did he remove the head, look at the gasket and reassemble it with the original one? That doesn't work. Did he use RTV when he reassembled it?

Pull the spark plugs and turn the motor over by hand, using a wrench on the bolt that holds the crank pulley. If it's really hard to turn over, you may have a bad bearing."

"I put it back together by the

"I put it back together by the book. Seems weird that it just won't get past 2200rpm in gear, but will seem to run right in neutral. I can idle around the lake at 1000-1500 rpm without an issue. Could there be something with the drive that is limiting the speed? I kept thinking it was something with the fuel system that was impacting me only when the boat was underway at high rpm. It has a bravo III drive with dual props."

"You still need to go through

"You still need to go through the diagnostic steps in order to pinpoint the problem. Once you rule out the motor, then look at the drive. If you can't go faster than xxx MPH, you need to test things. Is it getting the right fuel/air mix, is the timing correct and stable, is the valve train adjusted correctly and in good condition?

Does it make any strange sounds when it goes bad? Is there any sudden jerkiness, clunks, tapping, bogging intermittently? Have you hooked it up the the timing light under when this happens?"

"I will do a vacuum and compre

"I will do a vacuum and compression test. No noise. I will readjust the valves. We did so by the book. adjust one set when cyl 1 was at TDC, then the others when 6 was at TDC. But there was great lash then with some valves that we first adjusted. We tightened them down. Did not seem that the book was right in its instructions. I will go back and do again and assumed it is right. It is a Selco book. I may get a new coil also."

"Get the info from a GM manual

"Get the info from a GM manual for adjustng the valves. I don't remember doing it that way when a friend and I did the valves on my truck (he worked for GM in V8 Powertrain developement for about 25 years).

Or, google it. The instructions are bound to be on the 'net."