Final tweeks needed, please help

[angel_guardian]

OK I have an 82 merc black max 150 v6; finally after a long grueling year she's alive and running pretty well, the motor is on a 900lbs 78 glastron ski boat. Today I had the boat running about 45 mph after about half hour of playing with throttle and warming motor up at about 5-10 mph. Everytime I would give it throttle it sounded as if it was geting too much fuel and then would level off acting like it was too much of a load. And then after a few high revs with Fast Idle bar on throttle it jumped right up to 40-45 mph no prob... Also noticed it wasn't "peeing" very well. Just a steady trickle. After about 15 min alarm started sounding. I've also noticed there is not much play in the throttle. Its either 5-10mph or 40-45mph anything in between motor spits and sputters and usually dies. I've got to go wot from the beginning and even then it skips for a sec then kicks in. Boat is planing well and I'm trimming up a little at a time to get peak performance. Any advice on one or all issues would be appreciated. Also, my wife asks please give advice that will not cost anymore money

 

[oldman570]

Re: Final tweeks needed, please help

If the water pump has not been replaced lately you might want ti check it out. Might want to check the settings on the carbs and clean them also. or run some Sea Foam in the fuel. You can buy a can of Power Tune at most local dealers and use it to help clean the carbs without having to tear them off the motor.
Oldman570

 

[Silvertip]

Re: Final tweeks needed, please help

If the alarm went off you have an overheat situation. Continue to run it that way and you will be looking at a rebuild or a new engine.

 

[angel_guardian]

Re: Final tweeks needed, please help

I have already taken carbs off and cleaned them several times thoroughly, and also bought a can of Sea Foam. Now when you say check the settings, I have tried to adjust the fuel/air mixture screws but the first time I adjusted they were as tight as they would go, and then any adjustment by loosening them made it worse. I opened them up one full turn and then tightened them 1/8 of a turn at a time. Each run stayed horrible until they were back to tight position. As far as water pump goes I will look into that, that is one thing I have not replaced yet (hence the no more money comment).

 

[angel_guardian]

Re: Final tweeks needed, please help

Also, one more question... What is the fuel/oil ratio on a 5 gallon tank? Premix needed for this motor but I never found the specs on that and just had someone else on here tell me to put a full quart into the tank. Not sure if that is accurate or not.

 

[coastalrichard]

Re: Final tweeks needed, please help

Angel...that's a sporty mix (20:1) and could be one reason for the rough running. A typical fuelil mix is 50:1. I'm with Silvertip...you need to make sure the LU service gets done ASAP. Good Luck!

 

[ajgraz]

Re: Final tweeks needed, please help

Summary:
-Idles only if idle screws are completely tightened down
-Has problems with transition into power
-WOT no problem

Sounds to me like the carbs are not really, really, cleaned; as in perhaps not all the little passages are truly cleared.

Are you using fresh gas? Is the whole rest of your fuel system (tank, lines, primer bulb, fuel pump, filter(s), fittings) clean and functioning properly?

 

[CharlieB]

Re: Final tweeks needed, please help

........... I have tried to adjust the fuel/air mixture screws but the first time I adjusted they were as tight as they would go, and then any adjustment by loosening them made it worse. I opened them up one full turn and then tightened them 1/8 of a turn at a time. Each run stayed horrible until they were back to tight position. ................

Idle mixture screws should NEVER be tightened more than very LIGHTLY seated or the seat will be damaged, usually rendering the carb useless.

Idle mixture is usually initially set to 1 & 1/2 turns out from LIGHTLY seated. This should give enough fuel to get the motor started IN the water and allow the motor to idle IN Forward gear.

Idle mixture MUST BE finalized IN the water and IN Forward gear to provide the correct exhaust back-pressure and load on the motor.

Adjust each mixture crew so to obtain the 'Best Idle Speed', make very small adjustments one at a time and allow at least a minute for any excess fuel in the motor to burn off and idle speed to stabilize before moving on the the next screw.

Once Best Idle Speed is done, each idle screw needs addition tuning to increase isle fuel to provide the additional fuel necessary for crisp acceleration.

Open each screw just the width of the screwdriver blade slot and test holeshot/acceleration by rapidly opening the throttle to WOT.

ANY cough, lean miss, bog, or hesitation proves a need for additional fuel. Open each screw another bladewidth. Repeat acceleration test.

Repeat to perfection.

It may be EXTREMELY difficult to adjust idle mixture with damaged idle seats, adjustments may need to be even smaller than just a blade width. If at all.