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Merc 57 bravo stall when wamed up under load

allenkkuhn

New member
"I have a similar problem to t

"I have a similar problem to these posts:

http://www.marineengine.com/cgi-bin/discus/show.cgi?tpc=12486&post=79546

http://www.marineengine.com/discus/messages/12486/172052.shtml


HELP - I have the same problem on a 2000 Merc 5.7 bravo -
stalls after warming up and throttling up. Cannot reproduce at the dock, only when under load. Tried rebuilt carb, new coil, adding additives to tank, new cap and rotor. I have not replaced the fuel pump yet or distributor sensor.
thanks - Allen"
 
"Did you change all fuel filte

"Did you change all fuel filters? How about the spark plugs; changed lately? What colors are the plug electrodes? Check the fuel vent line for a low spot that could hold fuel. Next time out, loosen the fuel filler cap if the tank is under 2/3rds full and see if it still does it.

Was the mixture set on the new carb? May need to make it slghtly richer if the plug color is off white."
 
"Did you change all fuel filte

"Did you change all fuel filters?

-fuel water seperator changed last month
-checked it - no water, clear fuel

How about the spark plugs; changed lately?

-not changed since early last year (50 hrs ago)
-with other 100 hour service
-maybe all 100 hour service items are due

What colors are the plug electrodes? I'll check

Check the fuel vent line for a low spot that could hold fuel. Next time out, loosen the fuel filler cap if the tank is under 2/3rds full and see if it still does it.
-(will do)

Was the mixture set on the new carb? May need to make it slghtly richer if the plug color is off white.
-checking plug color and will let you know
-carb settings not changed from rebuild shop
-noticed idle was at 450, but seemed ok

-since its only under load and hard to test (not at dock, 10 min trip to open water, and follow boat needed) - I am thinking after checking fuel vent line and plug color, replace all possibilities to get it fixed soon ?
-thinking of:
-distributor sensor ($50)
-fuel pump ($200)
-plug wires ($??)
-plugs ($??)
-replace fuel filter in carb again ($??)
-other ??

-}thanks again - Allen"
 
""-noticed idle was at 450

""-noticed idle was at 450, but seemed ok"

Back the strapped down boat into the water enough to cover the OD w/water, start it up and let it warm up to oper. temp. In neutral, set idle speed to 650 RPMs. Now put it into forward gear and reset idle to 650."
 
"hmmm - now you have me thinki

"hmmm - now you have me thinking


the boat is on a lift on a canal 160ft wide - with nothing behind it.

if I lower the boat into the water enough to cover the OD, tie down the lift cables and the strap the boat to the lift - and put it in gear - I could "theoretically" rev it up under load ?

then again - if this is the equivalent of a high school brake torque stunt - - I have seen too many dropped trans in my high school days - wouldn't want to launch the boat out of the lift onto the land
"
 
"Sounds like your power circui

"Sounds like your power circuit in your carb is going lean. Thus when you open the throttle you are getting lots of air, but insufficient fuel. When the mixture goes too lean, she quits. This will save you fuel, but the boat won't run very well.

If it used to run well, my guess is that you have some crud in your carb bowl that has plugged off the fuel passage to the venturi cluster.

If you are brave I suggest you rebuild it, or get a rebuilt carb.

BTW, the mixture jets only affect the idle and slightly off-idle mixture. They have no effect on mid-throttle or open throttle mixture.
Open throttle mixture is controlled by meter jet or rod sizes and fuel level in the bowl.

Rod"
 
"1997 Mercrusier 5.7 liter eng

"1997 Mercrusier 5.7 liter engine. 350 hours on it. Just put a new carbuerator on it. It runs fine. But on the first start of the day, tough to get it to start. Takes two to three tries. And does not seem to matter if I give it throttle or not. When it starts, it then smokes and kicks out fuel from the exhaust until it comes up to temperature. So the stern gets black build up on it from the exhaust and there is residue left from the fuel on the boat at the water line as well. When I turn it on and off during day, it starts just fine. Quickly with no throttle needed. Is there an adjustment for this? Thanks much."
 
Rod - back to the original pro

Rod - back to the original problem -
I had the carb rebuilt - but immediately came up with same problem - runs fine at dock - all the way upto the rev limit at 3300 RPMS

thanks again
 
"Could be fuel starvation.
Yo


"Could be fuel starvation.
You could T in a pressure guage at your carb inlet temporarily.
You should get 4-6 psig at all load conditions.
If not, suspect pump or filter(s).

Rod"
 
"I finally got the boat proble

"I finally got the boat problem solved with it "stumbling" under load

replaced bad fuel pump
replaced fuel line - it had a pinhole leak allowing air in, but not big enough to allow fuel out
setup second tank

and it worked - - my tank is steel, but has lots of sediment in the bottom and I have been using the gas station ethanol mix - my plan now is to get it cleaned/polished and add dry gas at every fill up


thanks again for advice and help !!!"
 
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