Bigger carbys & manifold on 9o hp v4

[arnobay]

My runabout fishing boat has an old 90hp v4 with carbies & manifolds from a larger motor perhaps a 115hp or something like that. It uses heaps of fuel & has too much power for me but I'm stuck with it. Very hard to control speed to a safe limit as it tends to run away and am constantly having to throttle on & off all the time. Can it easily be detuned with out changing carbies etc? Would a smaller prop help control speed? It feels like it hits a power band and takes off. the boat is a 15ft savage runabout. The carby numbers end with 15 so I'm assuming they may be from a 115hp. It has a domed manifold thing on the back of motor. model no. is A J90TLCCA

 

[racerone]

The 110 / 115 HP blocks of that era had the bubble / tuned exhaust.-----Or someone added that to your 90 HP block.-------The 90 HP blocks had smaller intake ports.------And installing a smaller prop is totally the wrong approach too.

 

[fdrgator]

You can try making and installing some restrictor plates between the carbs and intake manifold to reduce horsepower. No gurantee of the results and you are on your own since you are emparking into unknown territory. Well, not totally unknown, since the factory uses similar techiques to create various horsepowers from a common base motor.