I have a Alumacraft Magnum 175 CS ( 17' 11" )Deep Vee with a Merc. 115 4 stroke, with a rapture 13 1/4 by 17 stainless prop. The boat runs 42 mph GPS at 5800 RPM. It seems to be bow heavy with the spray exiting just in front of the drivers seat. I was told to peen the hull a little at a time and test it. Is there anything else I can do to increse performance, short of purchasing a larger motor? Is there any mild changes that can be done to the motor to increse performance, without voiding a warranty?

Oh yea the motor is mounted in the third hole with 2 above and 2 below for adjustment. The boat also gets out of the hole pretty good.

Thank You in advance for any help you can provde.

Jake

No trim and tilt??? on that 115 ??? trim the bow up until you hear the propeller start to cavitate...... then back it back down a little.

Boatman1, Yes I forgot to mention that I do have trim and the 42 MPH GPS speed is at full trim. The boat gets on plane good but I just can not get the bow up enough.

Jake

I have a 175 Magnum with a 130 Honda. I put a dolphin fin on it. It planes very well and does perform well.

Give Joe Ham at Advantage a call. He has setup more Deep V's than any other dealer in North Texas.

ADvantage Marine
972-495-5343

Jerry,

Thank You for the reply. I will call Joe today.

Jake

JL, got to say that the boat in the picture below has a doelfin on it 115 Evinrude........... yes I can trim it up or down a lttle bit........there is a very small range of trim before the motor cavitates......... boat runs just fine within the small trim range............. to pick up the bow in rough water I just run slower so the bow stays up.

Do you have heavy objects like a battery or heavy anchor in the bow compartment? If so move them to the middle or rear of the boat.

Not sure if 2 stroke info is applicable to 4 strokes but... my installation instructions for a 2 stroke 125 Merc indicate the motor should be mounted in the lowest position unless the top speed is expected to be over 50. Then move it up one inch at the most. You may be getting prop slippage with the prop that high out of the water.

I would think you may also be able to use a prop with a larger pitch than a 17. I run a 19 on my 21' CC and get about the same top end as you at 5200 RPM. With your extra rpm range (6000 - 4 stroke vs 5250 - 2 stroke) your boat should fly with a 19 or 21 prop.
Good luck.