Boat speed and porpoising

[JUSTWINGNIT]

Hey guys I have a 2005 alumacraft tournament pro 175 cs with a 150 Honda on it. I have been reading on other forums about this boat with the same specs except for it having a 150 Yamaha on it and he says he is getting 48 to 50 mph out of it. Mine on the other hand is only getting 36 or so. It sounds like we are loaded close to the same. I would ask him but the thread was from 2006. Anyways I also get porpoising pretty damn easy at wot. Seems like I need to have the motor trimmed down so damn far to prevent it. The motor is "bottomed" out so to say. Do I need to raise it up a few holes and try it again? I was running a 14.5 X 17p aluminum prop until I wacked a damn rock. Any help would be great!

 

[PrairieGhost]

I'm running a 1750 Lund with a 130 Honda, and a Mercury 15hp pro kicker. Mine does 42 mph. If their are small waves it will hit 44 mph. Mine came out of the hole a little slow so I put one of those fins on the motor. It's up in about a boat length it feels like now. Also I don't get any porpoising now which it did before. Well, I shouldn't say I don't get any, but it trims out easily. Also before I couldn't lift my bow. Now I can lift until only the back half of the boat is in the water. I think it took away a couple miles per hour of the top end. 42 to 44 mph are my current speeds. I forget my prop pitch off hand, but I pitched it so 5500 rpm was all she would do when full throttle.

 

[shorthairsrus]

i have my stainless raised all the way up.

 

[ShootnBlanks]

Raise the motor
Hydrofoil
Trim Tabs
Solas HR titan 14.75x19

OR
stop bringing that Michelob keg in front of boat while fishing.....

 

[gonefshn]

Ditch the aluminum prop. They can't hold the nose up like a stainless. Try a few first though. Don't just guess. Typically, your manufacturer will have a recommended one if you call them.

 

[JUSTWINGNIT]

That is the plan. Just looked up the soles and went to Honda website and that is what was recommended. Going to check where the cavitation plate is in reference to the bottom of the boat tonight.

 

[pluckem]

I drove a yarcraft 18' side console with a Honda on it and it was a dog and also had porposing issue. If three guys were in the boat one would have to move to the front some to help it plane out. It wasn't my boat so I didn't play around with it much. I do remember the weight specs on those outboards was really high.

Find the recommended max RPM's of the engine and find prop selection (stainless) from there. However I don't think you will get close to 150 Yamaha performance.

Just an update, the engine mentioned above was a 135hp (I believe it was same platform as the 150hp). Could have been the main reason for the lack of performance. Especially when compared to the 125 class engines which had some considerable weight savings.

 

[LBrandt]

I put a hydrofoil on my alumacraft and it took care of the problem.

 

[revolutionz]

I needed to put a hydrofoil on mine too....trim tabs helped, but not as much as the hydrofoil did.

 

[Allen]

WHile you may have other issues, you won't ever regret putting a hydrofoil on that setup. My Lund is fairly similar and a hydrofoil makes it a much nicer ride.

 

[ndskeeter]

I understand you're dealing with porpoising and the hydrofoil should take care of that but you aren't going to get any speed if the motor isn't trimmed out. 36 mph can easily turn into mid 40s if you trim out all the way.

 

[dragoneyes]

Stainless steel prop, Cobra Edge stainless steel Hydrofoil. Great hole shot elimanated porposing without compromising mph. Alumacraft 175 with Yamaha 150 and 9.9 kicker on back can hit 50 mph in right wave conditions. Way to fast for my liking.

 

[all4eyes]

Hydrofoil and a call to Brainerd Propeller will be all you need. They will have you propped in 1 or maybe 2 tries. Free exchanges as long as no damage to the prop.

 

[shorthairsrus]

Part of the is issue is they are building the antibcavitation plate narrower especially on mercs. I don't know why. With my Evinrude I have not had the issue.

 

[JUSTWINGNIT]

Thanks guys! I will be calling Brainerd propeller for sure one of these days and getting a hydrofoil. Do you think I should lift the motor up? I checked last night and when it is tilted all the way down it loos like the cavitation plate is about 1" above the bottom of the center of the boat. Does that sound right?

 

[ndskeeter]

I would leave your motor where it is until you are actually able to run the boat and see what you can get for performance. If you've been running with the motor trimmed down then you really have no idea if your motor height needs to be changed.

 

[Allen]

http://media.channelblade.com/boat_...s/dts/dealerlibraries/8441/copetipstricks.pdf

Interesting read on motor height, and other things.

 

[JUSTWINGNIT]

Ok...so I borrowed a 19p stainless tempest prop from river city. Got the boat out today and with me the wife 2 small kids 1/2 to 3/4 tend of fuel and gear I got 39.7 mph. The porpoising was still there but better. Got the rpms to 5600 ish. Going to call brainerd tomorrow and also get that cobra hydrofoil. It's getting better!