Mercrusier 140 low power

[Logan.jacobs]

Okay, so here is the deal. Couple of months ago i bought a 1986 four winns 160 marquise that needed some interior work and some wiring work done. After I've fixed all the interior and wiring problems, took it out to the lake and it seemed low on power. The boat came with the mercrusier 140. The boat takes about 1 minute to plain out and the engine will not go above 3000 rpm (Redline 4800) and tops out at about 27 mph (gps) with 2 people. So, started researching what could cause the issue. After weeks of researching and trial and error. I can't figure out the problem. This is a list of what i have done.

New flamethrower coil 3.0 ohm (wired correctly without resistor wire)
New spark plug wire
New cap and rotor
New spark plugs (gap set to 0.035)
Checked timing and set it to 6 degrees BTDC
Throttle cable adjusted properly
Switched to new electric fuel pump and fuel pressure regulator (set to 6 psi)
Cleaned the air filter
Did a compression test. All cylinders around 150 psi
Mechanical oil pressure gauge. Motor runs at 43 psi at 3k rpms
Changed the oil Multiple times. No water in the oil at all
Mercarb 2 barrel rebuilt. Twice!

The carb was rebuild twice because i realized that the accelerator pump wasn't pushing fuel out of the venturi after i rebuilt it the first time. fixed now. But the boat will still bog for a second under acceleration. I have messed with the air/fuel screw quite a bit. I currently have it turned out about 4-5 full turns out. The boat does not bog as bad when it's that far out but now puts out a little bit of white smoke for some reason. It also smells like its running rich. But the motor runs about the same besides the bogging with the idle screw all the way in. Like you can't lean the motor out. Also, i have checked for vacuum leaks and have not found any.

I believe that is everything i have done so far. If i remember anything else I'll let you guys know. The boat has been very frustrating to deal with because I've been chasing this problem for a couple months now. Any help or suggestions would be greatly appreciated. I'm only 18 years old so buying a newer and nicer boat just isn't an option right now.

Thanks for your time guys
-Logan

 

[Bondo]

The boat takes about 1 minute to plain out and the engine will not go above 3000 rpm (Redline 4800) and tops out at about 27 mph (gps) with 2 people.

Ayuh,..... Welcome Aboard,...... Great to see young guys gettin' into Boatin',......

Is the drive the original 1.98:1 gear ratio,..??..??

What pitch prop is on it,..?? might need a lower pitch,......

 

[Tycer]

Howdy, I’m not seeing you changed points and condenser. I think the ‘86 still has them.

 

[Rick Stephens]

Howdy, I’m not seeing you changed points and condenser. I think the ‘86 still has them.

Good catch.

 

[Ed Harris]

Since your going to be changing points and condenser you might as well take the points plate out of the dizzy and make sure your advance weights move freely and d are not rusted up. Clean with a Dremel and wire wheel if you have one.