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Dominick
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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2005 Mariah Mercury 3.0 l tks serial number 0W331683 Maximum

Customer Question

2005 Mariah Mercury 3.0 l tks serial number 0W331683
Maximum rpms 3300 after moving to the front of the boat to get it up on plane. There isn't a real hole shot, no power.
Timing set per mercruiser specs 1 degree btdc all filters fuel on the bottom of fuel pump water separator and inline at carb changed. New fuel pump new plugs wire cap and rotor drained tank new fuel rebuilt carb new brass float new anti siphon valve, bypassed water separator with fuel line same result.
Submitted: 2 months ago.
Category: Boat
Expert:  Jason replied 2 months ago.

G​ood morning my name is***** compression, fuel pressure, spark output, and timing advance been checked yet?

Customer: replied 2 months ago.
Compression was done 164-170 On the forth stroke.Fuel pressure is 5 lbs at idle new pump also.Timing verified at idle in timing mode and after reconnected around 14 degrees and total timing at 2400-2800 was around 23 degreesSpark was checked with inductive rpm gauge. Output was not measured don't have the ability. All plugs burning evenlyCoil was within spec checked ohms perIgnition module was within spec checked ohms .
Expert:  Jason replied 2 months ago.

Got it. Is there a story to this engine. Have you ever personally seen it run correctly? Have you tried running it off of a portable fuel tank in order to rule out any kind of tank issue?

Customer: replied 2 months ago.
Just bought it when I first ran it I got 3200 -3300 rpms max and no real power to get up on plane.
I verified the tach is within 100- 150. I changed the float last weekend to brass because the original float when set in a cup of fuel was absorbing it and sunk about 1/8 inch below the dot.
When I put the mercruiser rebuild kit I. I didn't use the new spring for the needle valve under the float because it was very weak so I used the original spring. I actually got less rpms after the float change 2800-2900 rpm. I'v now put the solid brass piece in with no spring to try. I have not tried a separate tank. I have verified that the exhaust flap is in place and no obstruction through to the stern. Your thoughts?
Expert:  Jason replied 2 months ago.

Well, since you have never seen it make full power this is going to be a lot more difficult and you are going to have to check the gear ratio on the sterndrive as well as the propeller sizes. The ratio will be stamped on the upper half of the sterndrive, and the propeller will be stamped a size someplace on that. Find that information and let me know what you get for numbers.

Customer: replied 2 months ago.
2.0 ratio 14x19 prop it's stock original for an 18' lowrider this boat doesn't have barely any time on it and it never left the freshwater lake it was born on here in Virginia.
Expert:  Jason replied 2 months ago.

What you will need to do next is confirm the gear ratio is correct. If a gearing change was ever done the stamping on the unit might not match the actual gear ratio that is in the lower unit. Remove all of the spark plugs from the engine. Line up the mark on the balancer with the mark on the timing tab on the engine. Then go to the propeller and make a mark that goes from the side of the propeller over to the side of the lower unit. Turn the engine 2 full turns by hand and see if the propeller makes 1 full turn, or less than 1 full turn. Let me know what you find.

Customer: replied 2 months ago.
2.0 ratio 14x19 prop it's stock original for an 18' lowrider this boat doesn't have barely any time on it and it never left Lake Holiday. thanks
Customer: replied 2 months ago.
Actually the needle was vibrating rapidly at 16 the timing advanced to only 8 btdc after setting it at 2 atdc. I didn't turn the motor off before I hooked the wires back up. Does it advance differently if it's shut off then hooked back up? Idle at 700 rpm warmed set up timing mode the rpm drops adjust timing to 2 atdc shut off motor hook back up wires start and see where it idles at 700 rpm correct? thanks
Customer: replied 2 months ago.
What is the length of spark in a tester supposed to be? Can the oil pressure switch affect the coil output if it's reading incorrect?
Customer: replied 2 months ago.
Hello