150 hp starcraft inboard , question about puting 2 propellers instead of 1

[Sceptre]

I broke my prop on my 140 starcraft inboard
when I give full throttle the rpms dont go above 2800 and when i try to haul someone on the tube it doesnt go faster den 20km/h so i was wondering what I can do to make the boat go faster they sell thouse things you can put above the prop looks like whale tail to make the front stay on water or I was thinking of puting 2 props

[Jango]

You need to find out why the motor will not rev up? Is it an engine problem or due to load on drive system? If you're using a broken prop, get it fixed or replaced. If it has too much pitch or Dia, it will not get to max rpm. If somehow you could install Two props, it will not solve your problem

A whale tail is used to raise the back of the boat quicker to get on plane and probably will not help much.
If the correct prop is being used, I would make sure the motor is in tune and next look for excessive weight in the boat or damaged prop/drive system

[Sceptre]

hmm thanks for the adivce i think its the motor

[Fanie]

It's the motor or you have gone overboard on the prop

Those 'to make the boat go faster they sell thouse things you can put above the prop looks like whale tail to make the front stay on water' won't make the motor faster, they help to get quicker on the plane but with a little less at top speed.

whale tail