help me with the outboard problem!

hello, please tell me what shoud i do in this case:i have a boat with transom height 39cm and an mercury outboard whith short shaft with hydrofoils, and it is mounted on transom, hight with 4 cm above and have problem with a big wave to the back of boat and spray wather. if i put down to normal the outboard this wrong wave disapear?the speed will be decreased? the wave is very big, short,and is too up from the idle line of water, is like a big mountain near the outboard aprox.1 meter close. the engine has 15 cp and the boat is 5 m long , 1,30m lengh. it is posible to be the engine mouted too high on the transom? thank you and sorry for my bad english!

Re: help me with the outboard problem!

Transom is for short shaft motor.Remove the foil and try it.
I believe the boat is about 16 feet. Can you tell us the dry weight and typical load?
Is the boat fiberglass? or Aluminum?Is 15 cp 15 horse power?What is brand and year of motor. Boat is likely under powered with a 15.What is the maximum speed.Motor could be a little high but try without the foil and tell us how it performs.We need the prop size,usually on the barrel or under the prop nut.
something like (9" X 9" ) Diameter X pitch. also need the present maximum rpm and speed with a light load.

Re: help me with the outboard problem!

the boat is made from fiberglas 120 kg, and the transom form iz like an U,not V,or plane.the boat can handle with 20 power horse ( in boat specification).before the hydrofoils the boat could'n go well with this engine(15 horse power- standard propeler from the mercury ), the bow it was too high like an aeroplane(this happens with the engine putt on corect transom distance like in engine manual specification ); after this experience , it was mounted up on the transom whith 3-4cm in hope to go in good conditions but the same problem is apper.after the hydrofoils mountage, the boat make a real progres but the new problems apear. is not wheight inside the boat or bad distribuite.tell me if i put down the engine to normal height on transom i will lost the speed or the speed is beter?

Re: help me with the outboard problem!

the boat is made from fiberglas 120 kg, and the transom form iz like an U,not V,or plane.the boat can handle with 20 power horse ( in boat specification).before the hydrofoils the boat could'n go well with this engine(15 horse power- standard propeler from the mercury ), the bow it was too high like an aeroplane(this happens with the engine putt on corect transom distance like in engine manual specification ); after this experience , it was mounted up on the transom whith 3-4cm in hope to go in good conditions but the same problem is apper.after the hydrofoils mountage, the boat make a real progres but the new problems apear. is not wheight inside the boat or bad distribuite.tell me if i put down the engine to normal height on transom i will lost the speed or the speed is beter?

Re: help me with the outboard problem!

I think 120 kg is about 250lbs. with a 15 and one person it should run about
19 to 25 mph.And perform strongly. Is the motor trimmed in (propeller closer to the boat)? "Transom is a U" do you mean the boat has a tunnel?
I think you have a motor problem.What year is the motor? It may be running on one cylinder. Its not unusual for a motor to seem fine on one cylinder except for a lack of power.