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Mercruiser problems above 4000 RPM

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wyomingman

New member
I had my 2002 Mercrusier 4.3 MPI, serial number OM322808, Alpha One out for the first time over the weekend. The boat started fine, idled fine, excelerated good and ran smooth up until 4000 RPM. Once above 4000 RPM the motor would surge up and down in RPM's jerking the boat forward and back until I throttled down below 4000 and then it ran smooth. I ran it all day long below 4000 RPM's with no problems. Any ideas what is causing this? would like to get it fixed before the holiday weekend in 4 days but the shop cannot get it in. I did take off the fuel water separator and will change this. The boat was stored over the winter with stabil but the 55 gallon tank probably only had about 15 gallons in it. Is moisture causing this problems? but like I said it ran fine below 4000 RPM/ Please Help!!!
 
Seems like a fuel starvation problem...if changing the fuel filter and water separator doesn't help, try temporarily using an auxiliary gas tank filled with fresh fuel to confirm the problem is fuel related
 
I'm sorry to say this, But your going to want to sign up and download this Merc service bulletin. Your serial number is within range.
You will need to see and carefully try the second half of the bulletin, Page 3 of 3, Or you really should have a Mercruiser dealer do it for you for your safety.

Either way make sure no other boats are around you when someone tries this procedure while out on the water, Because shifting will be affected while trying the test.

http://www.4shared.com/document/i5e2WwVR/Mercruiser_Service_Bulletin_20.html

V6 and V8 GMEFI with No Start, Engine Miss-Fire or Engine
Shut-off Conditions
Models Affected
Model Serial Number or Year
MCM V6 4.3L MPI 0M322781-0M645782
MCM V8 5.0L MPI 0M320415-0M642305
MCM V8 350 MPI 0M320590-0M642305
MCM V8 MX 6.2 MPI 0M320614-0M642305
MIE 350 MPI Tow Sports 0M310010-0M391684
MIE 350 MPI Inboard 0M310001-0M391684​
MIE MX 6.2 MPI Inboard 0M310008-0M391737

Good luck.
 
Check your distributor cap. Also check the hose clamps on the exhaust elbows. I had one with a broken hose clamp, spraying water on the distributor at higher RPM's
 
The engine does not stall or backfire. Is there another in line fuel filter somewhere besides the fuel water seperator. I will check the exhaust elbows for water leakage. Another question, how does an engine go from runnign fine to all of a sudden being a timing issue?
 
Wrong words used on my part, but still the same part. I'm gonna have to polish up and use exactly the correct words here from now on.

How does it happen that fast only g-d knows. Moisture is a mother f--ker.

Merc knew about this problem and put out the bulletin i guessed after 45 years working on anything with a motor.

Tech i guess is a younger guy with access to merc chit i don't have.

Dock is good, real real good .

The future belongs to him and others like him.

Good luck !
 
If you don't find a problem with the distributor cap and rotor, you need to hook up a fuel pressure gauge and take some readings. Should be between 40-43 PSI of fuel pressure. If you have more or less you need to let us know.
 
Hi guys,
I have the same issue, i have a bayliner 2052 with mercruiser 4.3 v6 alpha one year 2000 and the problem is that the boat rpm are bouncing for 100-200 rpm + or - and the boat wont go ower the 4000 rpm... and some times whet i crank it it fires but working for about 20 seconds and than stops... no mather how many rpm?? That does for few times and than it ctarts. I hawe changed the plugs, all 7 cables and changed al filters and changed that thing which is connected to electro distributor other side of the center cable ( don't know how to say in english..)

Please eny help if somebody knows what could be wrong?
I have in mind fule pump or reley of the fule pump beside the oil filter?
Thx for any help
Ziga
Sorry for my bad english language
 
Ziga said:
Hi guys,
I have the same issue, i have a bayliner 2052 with mercruiser 4.3 v6 alpha one year 2000 and the problem is that the boat rpm are bouncing for 100-200 rpm + or - and the boat wont go ower the 4000 rpm... and some times whet i crank it it fires but working for about 20 seconds and than stops... no mather how many rpm?? That does for few times and than it ctarts. I hawe changed the plugs, all 7 cables and changed al filters and changed that thing which is connected to electro distributor other side of the center cable ( don't know how to say in english..)

Please eny help if somebody knows what could be wrong?
I have in mind fule pump or reley of the fule pump beside the oil filter?
Thx for any help
Ziga
Sorry for my bad english language
Click to expand...

Hi. did you ever soulved your problem? i have the same motor and problem.
 
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