Mercury 1150/1350

[Gmcviper]

The serial number on the motor matches a '77 1150 but the cover says 1350 and the guy I bought it from said he pieced it together from a couple motors. just wondering if there is a way to distinguish the powerheads easily? I can only get 5000 rpm out of it on a viper with a laser2 22pitch prop is this normal? I have seen guys talking 5800-6000 rpm. I checked and carbs are opening all the way. any help is appreciated thanks

[milkdud]

The 1350 block was originally painted silver with twin fuel pumps on the side. The 77 1150 should only have one fuel pump on the cowl. If the serial number matches a 77 1150 I would believe that. Easy to just put a 1350 cover on in about 1 minute. The 1350 and the 1150/77 do not share the same mid bolt pattern.

Both the 1350 and a 1150 should pull at least 5500RPM. If less your either lugging it or something is not right with the motor. Most Inline 6's I like to prop to run closer to 5800RPM Max . Except the 90 that was made in the 80's, it lives at lower RPMS.

Set up correct that 1150 should pull that 22 pitch prop I would think on a viper.

one thing to check tho. The 1350 has a higher gear ratio. 1.78-1 vs the normal 2-1 . Its possible the guy put the 1350 lower unit on it which would lug the motor if your borderline on your pitch.

Mark your flywheel with a dot. pull electrical cables off shift into gear. turn flywhell by hand, might need to pull the plugs. It should turn exactly 2 turns per 1 turn of the prop. If the prop turns 1 turn quicker than the 2 turns of the flywheel you have a 1.78 lower unit, and you may need to adjust your prop.

But all things considered you should be able to pull a 24 pitch prop with a 2-1 on a 1150. and a 22 with a 1.78 on a 1150.
C

Conrad

[Gmcviper]

I haven't checked ratio but either way it should get at least 5500 regardless. what would cause Iit not to rev? Could the timing be off or something with the reads? Or is my tach wrong there is a rotary switch on back numbered 1-6 and it is in#5 but I don't have a manual that tells how to select position. But then on gps it only goes 51 mph ive been seeing guys going in the 60's with same setup. That's what makes me think it isn't revving all the way.