Help Merc 260 making me want to pull my hair out.

what the boat is doing along with todays observations.... the engine starts and idles fine and runs fine until between 1800 and 2200 rpm and then it starts surging the RPM's drop and then rev back up some and then drop and rev back up some. If you pull back on the throttle it goes back to purring along like a kitten. This seems to be happening just as the secondaries begin to open. Furthermore it begins popping out of the carb ALWAYS the CARB never the exhaust. I am at my wits end at this point there is so much new stuff on the motor I do not know what to do next. It has new heads, new pertronix IGNITOR II distributor, new manifolds, and carburator was rebuilt this spring, The deck was just replaced and along with it the fuel tank, all the fuel fittings and the fuel water separator. It seems to also be burning a little oil but that could just be surface oil as I had an oil leak. I am also going to post this in the engine help section. My thought is I need a new carb but I don't know any help would be appreciated

Here is what has been checked so far.... Removed anti siphon valve.... changed fuel filter.... checked timing... dissassembled carb and check float levels and free movement of needle and seat... checked timing again... ..... tested different engine trim postions.... Removed the little screen filter at the carburator... and the last thing I tried was bending the arms of the secondary valves just slightly to allow the fuel to begin flowing a little sooner. ABSOLUTELY NO CHANGE in performance still dies at 1800 to 2200 RPM:facepalm:

Re: Help Merc 260 making me want to pull my hair out.

have you checked to make sure the timing is advancing??

Re: Help Merc 260 making me want to pull my hair out.

no but it is a BRAND NEW distributor not a converted one I suppose I could check it anyway

Re: Help Merc 260 making me want to pull my hair out.

ryanmech said:

no but it is a BRAND NEW distributor not a converted one I suppose I could check it anyway

Click to expand...

just because it is brand new doesn't mean it is working properly

yes, do check it to make sure it is advancing properly

Re: Help Merc 260 making me want to pull my hair out.

went and checked the advance it is 33deg total at 3000 RPM merc spec is max 34 min 30 so that is good several people have mentioned that I should install a flame thrower II coil in it and by pass the resistance wire does this seem like a valid solution

Re: Help Merc 260 making me want to pull my hair out.

ryanmech said:

by pass the resistance wire does this seem like a valid solution

Click to expand...

uhhh....well,

did the new distributor come with instructions stating if you need a new internally resisted coil, or if you can still run the old coil with a resistor wire or a new coil with a resistor wire??

Re: Help Merc 260 making me want to pull my hair out.

if you read the instructions.. you are more confused that when you started regarding factory coils ..... so I am thinking this is my next avenue

Re: Help Merc 260 making me want to pull my hair out.

What year is your engine? Better yet what's the Merc serial number?
Why did you replace the distributor? was it doing the same thing?

new pertronix IGNITOR II distributor

Click to expand...

Was this a marine distributor? Was it a complete distributor or just the conversion kit?

Re: Help Merc 260 making me want to pull my hair out.

Complete distributor and yes it marine

Re: Help Merc 260 making me want to pull my hair out.

So does this distributor kit completely remove or bypass the Mercruiser Thunderbolt Ignition controller?

Did you replace the fuel lines and the pump? You could plumb in a pressure gauge in the fuel system. That wouldn't normally be needed, but it might point out an issue.

Re: Help Merc 260 making me want to pull my hair out.

What about all the other questions????????

What year is your engine? Better yet what's the Merc serial number?
Why did you replace the distributor? was it doing the same thing?

Click to expand...

Re: Help Merc 260 making me want to pull my hair out.

Sorry Don didn't see the other questions.

This is a 1982/83 merc 260 it does not have nor has it every had a thunderbolt module the distributor was replaced because the previous distrubutor had a pertronix upgrade in it that got shorted out when it was installed incorrectly(my bad hooked black wire to ground not to coil.) The cost to replace the module vs the cost of the new distributor with the module was negligible as I got the distrib on sale from summitracing (YES It really is marine).

When the new tank was put in it required some rerouteing of fuel lines so yes they were replaced I have checked the fuel system with a vacuum gauge and I don't remember what the reading was but I had the laptop on the boat and was looking at one of don s other posts and it was in range he specified.

At this point I am down to bad rebuild on the carb, wrong coil, or something REALLY messed up internally to the engine.

On the Carb side of things.... rebuilt quadrajet or edelbrock 1409 ..... what is the fuel economy difference/performance loss with the adapter plate.

Re: Help Merc 260 making me want to pull my hair out.

I have ordered a edelbrock 1409 and assorted pieces to convert (fuel lines and adapter plate) and a new coil.. They will be here tomorrow ... depending on the time I might get a ride tomorrow before work... otherwise maybe wendsday before I head to Maine for my 4 year old nephew's funeral lifes supposed to be a bi*** before you die... God rest his soul

Re: Help Merc 260 making me want to pull my hair out.

Was anything done with the canshaft? Worn out lobes or lifters will cause popping through intake/carb. Can you rev it up in neutral without it popping? Could be fuel starved, need to check fuel volumn out of pump.

Re: Help Merc 260 making me want to pull my hair out.

Go with nikogto +1!

Re: Help Merc 260 making me want to pull my hair out.

Okay now I am hairless .....new carb no change ....new coil .... checked plugs ... firing order ... new fuel filters .... same issue wtf

Re: Help Merc 260 making me want to pull my hair out.

Let's start from the beginning here.
1. When did this start? or How did this problem come about to begin with? did you buy it this way, did the problem start all of a sudden, or build up over time.
2. Was anything installed on the boat immediately before this started.
3. With the engine running at 1200 rpm, what is the voltage on the + terminal of the coil.
4. What spark plugs are you running in it?
5. Have you done a compression test? If so, what are the results.
6. Have you checked the fuel pressure going to the carb? If so, what was the pressure.
7. Have the valves been adjusted recently?
8. Have you done any of these fuel system tests in this link. http://forums.iboats.com/showthread.php?t=167561 if so, what was the results.
9. Do you have a water seperating fuel filter. If so, has it been checked for water, was there any water?
10. Have you tried hooking up a vacuum gauge to intake vacuum and checking it while running.

I will bet when these questions are answered we will know why your engine runs poorly.

Re: Help Merc 260 making me want to pull my hair out.

Agre with Don, Just have a few to add.

How did you adjust the Valve lash?
What did the old lifters and cam look like?
New Timming chain by chance?