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Duane2135

More fuel issues

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17 hours ago, cyclops2 said:

I know you have checked that the Choke Valve is wide open when heated up. Also that the SECONDARIES ARE OPENING COMPLETLY.AT 4000 rpms.

Are your secondary valves opened by a vacuum pot ? 

Or by MECHANICAL linkage ?

Having  a engine hatch open on a 40 mph boat is VERY risky !! SNAP / BANG  GONE.  I would do a safer way.

Find a place with FULL VACUUM available at about idle speed. Buy a long enough piece of vacuum hose to go between the 4 bbll secondary vacuum actuator/ dashpot & the high vacuum place on the engine. See if vacuum.......no vacuum ......fully OPENS & CLOSES the secondary air valve completely. You can almost do this with the boat & fenders tied to a strong dock. I have done it. Need the lines SECURE & EVEN tension.

A safer way is to buy a cheap vacuum pump at a auto parts store to checke the vacuum pot opening all the way. Engine stopped

I have a dog-house, not an engine hatch.  It is now strapped down by rubber clips with no more hinges.  This way it's easier to get to the engine to do quick engine drain and flushing.  I have hoses running to every drain point in the engine with valves on them, so all I have to do is open the valves and drain my engine of all the water.  I hated the hinges, because all  could do without unbolting the doghouse was check fluids.  So I'm able to drive at 40 with the dog-house moved forward, reveling the engine.

The secondary's are mechanical, and yes they open all the way.  I'm certain the boat is starving for fuel.  I'm waiting on a new anti-siphon valve.  When it comes in, I'll remove the old and check it out.

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  Look at the more pleasant side of your boat problems.

You could have a BRAND NEW BOAT with serious problems.  That really would sting.

Is that carb big enough ?  Enough CFM at W O T rpms ? Hot rod shops can tell. Could be a secondary metering rod problem or adjustment.

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You are absolutely right.  At least it's paid for ;) 

It's a 750cfm on a 5.7L engine.  If anything I would have thought it may be too big, but I'm sure it's the OEM carb.  I think Drew is on to something with the anti siphon valve.  I just don't want to take it off till its replacement comes in.  At this point, I'm pretty sure the problem is no longer a carb issue, after my recent tear down and rebuild of it.

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Bypass the siphon valve with a piece of tubing for a test run. Simple & positive check.

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Normally a starving / lean boat can start  missing /  getting rough. Just like adjusting the idle too lean.  Are you getting too rich ?  Smooth loss of power.  Do about a 1 minute run at  W O T then stop the  engine quickly. Check the plugs for getting darker / blacker than normal. Check them ALL. A plug or 2 may be breaking down under full load.

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Another possibility would be a plugged up tank vent. That would lead to creating a negative pressure on the tank after running a while and cause fuel starvation. Have seen that happen a number of times on boats and road vehicles.

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18 hours ago, Pops said:

Another possibility would be a plugged up tank vent. That would lead to creating a negative pressure on the tank after running a while and cause fuel starvation. Have seen that happen a number of times on boats and road vehicles.

The vent is clear, I check it every time I fill up by feeling the air rushing out as I fill.

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Is your fill gas cap vented ?  Does it have the correct gasket to allow air into the tank  all the time ? Someone may have plugged the cap vent hole or used a incorrect gasket.  Common problem at marinas that sell both types of items.  Try doing a high speed run with  the cap OFF. Another person wears a glove to prevent water splashing in the open fill pipe.

Still no wide open ?  Get a timing light & check the spark / ignition advance. Could be dead  Way retarded at W O T..  Smooth but no BALLS.

Get lucky Duane.

Shepherd or Wingnut can tell you how.   Take doghouse off. Get a driver. Be careful at W OT & 40 mph holding the timing light.  I tape the long leads out of the spinning belt path. If that checks out good.  Some body has changed parts in the SECONDARY part of the carb.  DIY strikes again. Or plugged up from fuel drying each winter. Not sure if you have both air & fuel tubes plus metering rods.  All need to be pulled & the numbers check out for that carb. Check that the metering rod linkage IS MOVING THE METERING RODS ENOUGH.  Ruler & feeler gauges are required on some carb secondaries

SOOO CLOSE.  To a great running boat.  Stay with it . piece of cake now.

Forgot.......Get correct instruction for adjusting your EXACT SECONDARIES.

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The correct CFM carb for the 5.7L depends on the drive.

Alpha 1 models used a Weber 9661 or 9665S carburetor which are roughly rated at 625 CFM.  The "6" in "9X65" indicates it is the 600/625 cfm Weber.  Same as Edelbrock 1409 series.

Duane's engine of course is mated to a Bravo 3, so it probably has the Weber 9770SA which I think was 700+ CFM. Some later 5.7 LX engines from 1996-97 used the Weber 9781 carb.

MerCruiser Weber pdf service manual below is for larger Weber 9779 and 9780, etc. versions used on certain big block V8 applications. I wish I had a paper version of the Weber carb manuals that I've had access to over the years.  PAGES 4 & 5 IN THE pdf below SHOW THE WEBER MODELS COVERED AT ANY RATE FOR THAT MANUAL.

http://www.marinemechanic.com/books/manuals/webber-carb.pdf

MerCruiser Service bulletin 97-9 sheds more light on things to check too.

http://www.marinemechanic.com/merc/distributors/mercurymarine/sterndrive/webber.pdf

Like the idea of waiting for the replacement anti-siphon valve. The aluminum threads typically get buggered up as soon as the valve is removed from the fuel tank fitting.

Truth be told, Duane and Cyclops have forgotten more about carbs than I'll ever know. Perhaps a stupid question, but is there a possibility there is a broken exhaust flapper in the Y pipe partially blocking the exhaust passage? Removing the drive should allow you to see if there are any flappers broken off and hanging out.

I found 3 out of 4 pieces in my y pipe last spring while checking engine alignment. They didn't block the exhaust off at all though, and I found no performance difference after removing them. I didn't think to take a picture, and they were not fun to remove being that far in. Picture below is for reference only. Nice thing about a Bravo is there isn't a shift shaft in the way!

Hope this helps Duane. 3:43 minute mark speaks about 'runs poor under load'.

 

Image result for broken exhaust flapper on mercruiser y pipe

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2 hours ago, Shepherd1 said:

The correct CFM carb for the 5.7L depends on the drive.

Alpha 1 models used a Weber 9661 or 9665S carburetor which are roughly rated at 625 CFM.  The "6" in "9X65" indicates it is the 600/625 cfm Weber.  Same as Edelbrock 1409 series.

Duane's engine of course is mated to a Bravo 3, so it probably has the Weber 9770SA which I think was 700+ CFM. Some later 5.7 LX engines from 1996-97 used the Weber 9781 carb.

MerCruiser Weber pdf service manual below is for larger Weber 9779 and 9780, etc. versions used on certain big block V8 applications. I wish I had a paper version of the Weber carb manuals that I've had access to over the years.  PAGES 4 & 5 IN THE pdf below SHOW THE WEBER MODELS COVERED AT ANY RATE FOR THAT MANUAL.

http://www.marinemechanic.com/books/manuals/webber-carb.pdf

MerCruiser Service bulletin 97-9 sheds more light on things to check too.

http://www.marinemechanic.com/merc/distributors/mercurymarine/sterndrive/webber.pdf

Like the idea of waiting for the replacement anti-siphon valve. The aluminum threads typically get buggered up as soon as the valve is removed from the fuel tank fitting.

Truth be told, Duane and Cyclops have forgotten more about carbs than I'll ever know. Perhaps a stupid question, but is there a possibility there is a broken exhaust flapper in the Y pipe partially blocking the exhaust passage? Removing the drive should allow you to see if there are any flappers broken off and hanging out.

I found 3 out of 4 pieces in my y pipe last spring while checking engine alignment. They didn't block the exhaust off at all though, and I found no performance difference after removing them. I didn't think to take a picture, and they were not fun to remove being that far in. Picture below is for reference only. Nice thing about a Bravo is there isn't a shift shaft in the way!

Hope this helps Duane. 3:43 minute mark speaks about 'runs poor under load'.

 

Image result for broken exhaust flapper on mercruiser y pipe

Wow, way to deliver a possible answer.  Thank you.

I have the captain call, and the issue is identical with the exhaust open or closed.  I also pulled the drive a couple months back for greasing the coupler and u-joint replacement.  At that time there was no sign of a broken flapper.  If you'll recal I'm on my third coupler so I now grease and check it annually.

I have the 9770SA

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I'm happy to say the issue is fixed.  It wasn't the anti siphon valve, but was the fuel line between the tank and fuel filter.  It looked and felt fine, but after replacing it the boat will now run foul throttle all day long. :)   My guess is air was getting sucked in the line.

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2 hours ago, cyclops2 said:

Can you still make the cruise ?

I'm going to hold off till next summer.  I've already cancelled my reservations, and I'd like the boat prove to me that all is well for some time before I go off shore.

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18 minutes ago, Duane2135 said:

I'm going to hold off till next summer.  I've already cancelled my reservations, and I'd like the boat prove to me that all is well for some time before I go off shore.

Smart thinking

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The boat owes you a vote of confidence.   Enjoy it.     :)

Almost forgot. Are you changing the rest of the tank to carb fuel line pieces ?

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On 6/10/2017 at 6:50 AM, cyclops2 said:

The boat owes you a vote of confidence.   Enjoy it.     :)

Almost forgot. Are you changing the rest of the tank to carb fuel line pieces ?

No, the rest of the lines are solid pipe, not rubber.

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On 5/16/2017 at 1:02 PM, drewm3i said:

Anti siphon is in between your fuel line and fuel pick up at the tank under your deck hatch. Get a wrench on it and it will turn off.

IMG_20170516_125853_zpsihzekxsg.jpg

And I'm not sure what carb is best, but I assume you're replacing a quadrajet? Those can be very finicky. Mine dripped fuel on shut down the whole time I owned the 2130. Rebuilds are very difficult to get right. I think Edelbrock has a direct replacement? Bolt it on and go boating to Bimini!

What is it a "check valve" ?

 

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If the fuel line comes off or gets melted in a fire it won't allow fuel to flow out of the tank. 

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On 5/31/2017 at 2:05 PM, Duane2135 said:

I have a dog-house, not an engine hatch.  It is now strapped down by rubber clips with no more hinges.  This way it's easier to get to the engine to do quick engine drain and flushing.  I have hoses running to every drain point in the engine with valves on them, so all I have to do is open the valves and drain my engine of all the water.  I hated the hinges, because all  could do without unbolting the doghouse was check fluids.  So I'm able to drive at 40 with the dog-house moved forward, reveling the engine.

The secondary's are mechanical, and yes they open all the way.  I'm certain the boat is starving for fuel.  I'm waiting on a new anti-siphon valve.  When it comes in, I'll remove the old and check it out.

Just a thought, on the secondaries. Just a quick check. I had someone punch the throttle in neutral fast and hard while I video recorded it. It was to dangerous to squeeze my face over the throttle plates (no head room). You should be able to see the secondaries kick in and open. I did not exactly record the opening rpm but I was alway under the impression they open at 3200 rpm's ( I sure it is in the manual somewhere)  They definitely opened up.  This was on a 350 magnum 1995 with a Weber 4 barrel. 

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Problem resolved with new fuel line between tank and fuel filter.  I apparently had an air leak.  Runs great now, all the way to 48mph on GPS.

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