Mercruiser 350 wont rev past 2000 under load.

[1990blackgt]

My 1986 Century was repowered 2 years ago. When i start the boat it starts right up, and idles fine. Under load, it won't go past 10mph, or rev past 2000 rpm. At idle, it will rev fine.

While chasing another issue, i replaced the carb with a 600 cfm edlebrock, new plugs, wites, cap, and rotor. New inline fuel filter, and water/fuel seperator. New bolt trim tabs, brand new SEI 1.47 outdrive. Today i ran it on an auxiliary fuel tank to rule out onboard tank/fuel issues. Still same problem. Any ifeas where to look next?

 

[1990blackgt]

Sorry for the typos

 

[alldodge]

Did it run this way before you replaced the carb with current one?
Which edelbrock carb model is it?

 

[Bt Doctur]

You need to :
Do a compression test, verify the plug wires and firing order are correct, verify that the timing does advance, check the fuel pressure

 

[1990blackgt]

Edlebrock 1409. It ran this way before carb.

 

[1990blackgt]

How would i check advance

 

[Bt Doctur]

If this is T-Bolt ign system do you have a V-8 trigger wheel and not a V-6 trigger wheel. Dont laugh, its been done before
locate the timing line on the harmonic balancer. set it to 0 and measure the distance from 0 to 10 degrees and paint that new dot to the RIGHT of the line, then from that dot, paint another dot the same distance.Start the motor , aim the timing light and check where it is at idle, then raise the rpm and it should move the dots to the left.
You initial timing plus the advance timing = your total advance

 

[alldodge]

Edlebrock 1409. It ran this way before carb.

In that case I would do a compression test next.

 

[Scott Danforth]

Compression test, check the fuel for water, check the filter for debris, check the anti-siphon valve. Its all covered in the stickies at top of the forum

 

[Rick Stephens]

Compression test, check the fuel for water, check the filter for debris, check the anti-siphon valve. Its all covered in the stickies at top of the forum

Cept he already did a test with an alternate fuel source to rule most of that out. Compression yeah. Timing advance, absolutely.

 

[1990blackgt]

Update:

Did a compression test. 140-150 on all cylinders.

Base timing was set at 14deg. Reset it to 8. Was on the boat by myself so I wasn't able to check advance.

Still no improvement.

Replaced the ignition sensor inside distributor. No difference.

 

[alldodge]

What is the prop pitch ?

 

[Bondo]

Ayuh,.... Welcome Aboard,.... I betcha the answer is in this list,....

 

[1990blackgt]

What is the prop pitch ?

I'm pretty sure it's a 4 blade 19

 

[alldodge]

With the 19 prop your slip is terrible, which is telling me you putting a lot of power to it but don't have enough to move the boat.
Which 1986 century model is the boat?

 

[1990blackgt]

Mirada 225

 

[alldodge]

The boat when manufactured weight was 4200 dry, so with a 1.47 ratio drive that is to high IMO. If the hull has taken on any water inside, this just makes things worse.

Case in point, my Formula weighs 10000 and had a 2.0 Bravo 3 and 415 hp, and turning 24 pitch props. Had the motor rebuilt and it now puts out 530hp and over 600 in torque. The builder said I should go to a 1.65 ratio drive, so I bought one. With the same props I could not get the boat on plane. Changed to 22 pitch set and I could get up but just barely. Removed the drive and put my old drive back on with 26 pitch props and it jumps right up.

I would suggest trying a 15 pitch prop, and if you cannot find one of them maybe a 17.
Next take the boat to a truck scale and weigh it