loss of power 5.7 merc

sea flower · Aug 23, 2010

I loose power when the 4 barrel opens. I've gone thru the whole 9 yards of the fuel system from the fuel tank (vacuum clean) replaced the water seperator 3 times,the carburetor with a reman. and twice a carb fuel strainer. The suction tube, hose, anti siphon check, everything except the fuel pump. It's an '83 260 sea ray original everything 100+ compression on all cylinders all new plugs, rotor and cap. TB4 ign. sparks on all cyl. great power up to 3k RPM. What's next?? even the marina mech. shruggs his shoulders.

Todd157k · Aug 23, 2010

Re: loss of power 5.7 merc

The plugs should tell the story. What do they look like after a run on secondaries ?

Bondo · Aug 23, 2010

Re: loss of power 5.7 merc

100+ compression on all cylinders

Ayuh,... She's all worn out....

sea flower · Aug 23, 2010

Re: loss of power 5.7 merc

thanks for the response fellas. the plugs are a nice clean tan and new.
Bond-o... worn out? I have more power with this thing than I had with my 71 torino...My friend told me that I may have a clogged jet. or the wrong size. I'm going to try to replace the jets with the old ones from the other carb. You see, I got taken down from Ethynol. This is when all my problems started.

Aloysius · Aug 23, 2010

Re: loss of power 5.7 merc

Maybe the secondaries are simply opening too early. Both Quadrajets and AFB's have an adjustable air valve. If this opens too early, air flow thru the venturis drops, and the engine stumbles. There is no accelerator pump on the secondaries.

sea flower · Aug 23, 2010

Re: loss of power 5.7 merc

didn't think there was any adjustment for this?? When I put this on it started right away. I just had to set the idle. It ran up to speed that first day then 2 days later I had the problem.

Aloysius · Aug 23, 2010

Re: loss of power 5.7 merc

What carb do you have?

Bondo · Aug 23, 2010

Re: loss of power 5.7 merc

Bond-o... worn out?

Ayuh,.... At 100psi per hole, it's a Core motor,.... Solid Runners should show 140psi,+ UP...

Not sayin' ya don't have other problems,.. but,.. that jumps out at Me...

sea flower · Aug 23, 2010

Re: loss of power 5.7 merc

I hear ya Bond-o The motor as I found has never been openned. there's at least 1000 hrs. Yeah I know but this thing is tight. The carb is a Rochester Quadrajet. Lots of new parts to keep up with decay. I got a new outdrive in 08 se106. Not terrible but light in construction. The whole thing has been on again off again as things break. I like working on it. The name is Re-Laxx. Nothing works on an old boat except it's owner....

Bondo · Aug 23, 2010

Re: loss of power 5.7 merc

Nothing works on an old boat except it's owner....

Ayuh,... No kiddin',.... I've got a couple in the water, 'n a couple more on trailers right now....

Aloysius · Aug 24, 2010

Re: loss of power 5.7 merc

Quadrajets are great carbs. The air valve is easily adjusted with a spring and set screw on the choke side of the carb..but it has to be off the engine to access it easily.

sea flower · Aug 26, 2010

Re: loss of power 5.7 merc

Haven't done anything yet. We've had some real rotten weather since last Sunday. Hope to work on the motor this week end. I'l let you know what I find

I'm havning fun on this forum. It's nice reading and helping.

sea flower · Aug 29, 2010

Re: loss of power 5.7 merc

Well it's 815pm here in buzzards bay. The Re-Laxx is back up and running WOT... I found another carburetor from ebay cheap and rebuilt it. guess what?? It runs like it suppose to. The Reman I got from Doug Russell Marine is junk..... I am PO'd spent close to $1000 trying to solve this issue. Now I have to see if I can get something back for it
Thanks everyne who gave me advice. It was the carburetor and the fuel line that caused my whole problem.

loss of power 5.7 merc

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