1998 90 ELPTO running on 2 Cylinders

[Bplank79]

1998 90 ELPTO S/N 0G723073 idles, lacks power and bogs out past 1/2 throttle. Pulled each plug wire one at a time and with another spark plug grounded to the motor, the bottom and middle cylinders changed the running at idle, the top cylinder doesn't change the running at idle, but the spark plug did fire. Installed new NGK BUHW-2 plugs. Compression is 120 psi on all cylinders. What next?

[JOE54]

better check fuel system /carb sounds like to me

[Bplank79]

Thanks Joe. Disassembled and cleaned all 3 carbs, replaced the fuel filter and the primer bulb, and fuel is fresh. We now have 3 cylinders running at idle, and seems to pull well at low end, but the motor bogs out when given more than 3/4 throttle.

[JOE54]

you check fuel pump for debri from degraded fuel line and or restriction in hoses/ anti syphon valve

[Bplank79]

Cleaned fuel pump and installed a new diaphragm kit. Pulled carbs apart again, no debris or blockage found. Fuel line is new. Switched anti-syphon valve out with one from a new tank. Starts fine, idles fairly smooth, and does not stall out. It no longer bogs out over 3/4 throttle, but overall lacks power and will not continue to build rpms at full throttle. It feels like the engine is being held back, and one or more cylinders fires or miss-fires sporatically.

[JOE54]

check spark when miss fire is occuring

[Bplank79]

After a water test now that the ice is out here, the issue appears to be resolved.
We found oil in the fuel tank, lines and primer bulb. Replaced the Oil Injection Check Valve #28 in the photos from the Service manual.

90hp Fuel Pump.jpg90hp Fuel Pump List.jpg

Thank you for your responses JOE54!

[JOE54]

[EuropeanAM]

Good catch!

Did you go through the Sync-n-Link procedure (complete) after the last carb removal? Very important.

[Bplank79]

We did not. But we will now.

Thanks Don!