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Mercruiser loss 200rpm forward/backward

L

lsteamgeo

New member
Hello everyone,


I need your help for my Mercruiser V8 5.7 L 350 (2001) + base Bravo 3.


In the neutral position, idle of my engine is correct (about 900 rpm), ignition is properly seated (about 10 °), the acceleration is linear.


In summary in neutral the engine runs perfectly.


However when I switched the forward (or backward), the engine immediately loses about 200tours/min to reach 700tours/min. When I accelerate, it is on the verge of stalling. I have to accelerate very slowly or giving small jolts to avoid stalling.


Where this can come?


Otherwise in navigation, once past the 1000 rpm everything works correctly. this problem is present at idle in forward or reverse. For maneuvering is really not practical, in addition to maneuver you have to play with the engine so it does not shutdown...


Thank you for your help.

Sorry for my bad English
 
Ayuh,.... Check the contents of the fuel filter for water, 'n debris,...

If there's crud in the filter, My guess is it's also in yer Carb, causin' yer problems,...

Btw,... yer motor should be idlin' at 650/ 700 rpms, in gear, in the water,...
 
Welcome aboard !

You have a carb ?

I think your rpm is set to high, should be around 650-700 in the water in gear in neutral.

900 would be ok on the trailer you will looses 200 rpm when in the water.

If you have a carbed engine then the carb needs a rebuild i believe your accelerator pump went.

Also you should see what psi the fuel pump is giving you.

Compression is good ?
 
Do you have a Fuel/Water Separator? Filter Changed? Dump it carefully into a clear container and let it sit covered for a little while and see if you have any bubbles sitting on the bottom, if you do then you have water in your fuel. If you don't have a Fuel Water Separator get one. When was the last time Fresh Gas was Added? Stabilizer?

When was the last time the Carb was serviced? Your Idle and possibly your Idle mixture needs to be adjusted if you find the Fuel is Clean and Fresh.

ps.. a 200RPM Drop from Neutral to either F or R is Normal, and Idle in Gear typically 500-650 ( I like 550-600 ).. Over 800 in Neutral is Bad and Not Needed unless the engine is highly modified.

good luck.
 
Thank you to all


I thought that lose 200rpm between the neutral position and Forward or Backward was not normal.


I now know that this is normal. I also learned that my idle is too high.


I will rebuilt my carburetor with a kit, I'll change the water/fuel filter separator and checking that the fuel is not contaminated.


I'll let you know.
 
When you are rebuilding a Carb there are many small passages that need to be cleaned and checked, NEVER use WIRE to Clean the passages this can damage them.
Solvents and Compressed Air are your friend, carefully and slowly do not rush the rebuild, take Pictures, Try to never blow dirt into the holes, all holes should be cleared from the reverse.
Youtube.com search "rebuild a carburetor" watch a couple times or even watch along with rebuilding, try to find a model close to yours.
 
kainon said:
When you are rebuilding a Carb there are many small passages that need to be cleaned and checked, NEVER use WIRE to Clean the passages this can damage them.
Solvents and Compressed Air are your friend, carefully and slowly do not rush the rebuild, take Pictures, Try to never blow dirt into the holes, all holes should be cleared from the reverse.
Youtube.com search "rebuild a carburetor" watch a couple times or even watch along with rebuilding, try to find a model close to yours.
Click to expand...


Thank you for your warning.


What kinds of solvents should I use? I have a NetCarb spray, is that enough?

I watched the youtube video, there's one on my carburetor (Mercab).

Thanks.
 
Get yourself down to a auto parts store, get a can of berrymans carb soak comes with a screen in the can, like a deep fryer.

Also get a can of compressed carb cleaner.And a carb rebuild kit.

With a clean area on a table or bench i place a old cookie sheet with sides.

Break down the carb and remove all the rubber.

Remove the jets they should just screw out.

Everything goes into the berrymans, let soak for a few hours.

Well it should be a couple hours a beer and a little work another beer and a little more work hell might be 5 hours who knows.

Remove the parts from the berrymans, start with the lower carb housing and blow it dry with compressed air, it clean?

I use the carb spray at this point. Then blow dry with regualted compressed air.

Piece by piece build it, make sure every passage is clean blow it dry and use compressed can carb clear blow it dry again.

Jets clean, Float, floating no gas in it ?

Push the float under water and if you see bubbles it's time to replace it.

Ok when you install the pin in the forks that hold the float are they pressing on the float tounge and not allowing the float to move freely ?

So if you did your job correctly the carb should operate freely, and when you install the adjustment screws be gentle.

Do not bend the tips. All the way in with them gently and out 2 turns to start.

Final adjustment on the water.

Have someone else drive about 2000 rpm maybe a little more and you do the final adjustment.

If you take your time and there are no distractions, you should be ok.

Good luck !
 
Thank you very much for all these tips!


I start disassembling the carburetor. In the carburetor bowl there are a variety of small debris.


I will clean everything.


Thank you again.


Sorry for my bad english
 
Make sure you get the correct carb base gasket or you will never get the idle mixture to adjust. A Mercarb requires a thicker gasket and not the thin type that comes in many carb kits.
 
guyjg said:
Make sure you get the correct carb base gasket or you will never get the idle mixture to adjust. A Mercarb requires a thicker gasket and not the thin type that comes in many carb kits.
Click to expand...

I cleaned the carburetor, change the seals. The engine runs perfectly. Thank you very much for your help!
 
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