1987 Mariner150hp v6 will not push boat over 5 mph

[Olddude26]

Looking for possible causes for bass boat not operating at normal speed? I have rebuilt the 3 WH carbs and replaced leaky floats, rebuilt the fuel pump , replaced fuel hoses & squeeze bulb, cleaned fuel tank and tank vent. I ran compression check and got 115 psi in all six cylinders. The 2 cylcle fuel system was deleted from previous owner. The engine will run at high rpm’s with propeller engaged when out of water. When lake testing the motor will run up to 2500 rpm before falling flat on its face. It may be water entering the aeration plumping giving the boat more weight. So it will plow through the lake but not get up on plane. Thx for the reply from a new member
And the new fuel is at 50:1 premix.

Cheers

 

[racerone]

Sounds like it is running on 3 of 6 cylinders.-----Test spark.----On the trailer , forward is still neutral as the prop has no resistance in air.

 

[Olddude26]

Sounds like it is running on 3 of 6 cylinders.-----Test spark.----On the trailer , forward is still neutral as the prop has no resistance in air.

Thx for the quick reply! I’ll pick up a spark checker from Habor Freight tomorrow and verify all coils are producing spark & also check each spark plug is doing the same.
I’ll get back to the forum on findings.

 

[Olddude26]

Thx for the quick reply! I’ll pick up a spark checker from Habor Freight tomorrow and verify all coils are producing spark & also check each spark plug is doing the same.
I’ll get back to the forum on findings.

Ok I checked the spark plugs and you were correct! All 3 cylinders on left bank showed a no spark condition. The right bank cylinders all showed good spark. The right bank went to the rear power pack and the 3 cylinders on the left bank or side of the engine went to the top power pack. What would you recommend before ordering new power packs? You tube said it could also be the stator or trigger..meaning pulling the flywheel.

Cheers