I have a 2008 Alumacraft tournament 185 sport with a 2008 150 Optimax. After break in the best rpm I can manage is 5200 rpms wot with 1/2 tank of fuel and one person and normal fishing gear rigged. the motor mounted all the way down and trimmed out just below porpoise. Currently has 19 pitch Mercury aluminum prop. ( came rigged from dealer) runs about 43 mph. Tried a friends 17 pitch Michigan wheel aluminum and it would tach over 5800 wot. Runs about 38 mph. Tach is calibrated and I have digital tach readout on the smartcraft gauge and they read the same. I would like a stainless prop. Any suggestions? Any one out there with a similar rig? how is yours propped? Thanks for your response in advance. I do notice that I can't trim up much and the boat starts to porpoise. Can only get bow up so spray is about even with my console.

My old boat was a Lund 1800 Explorer with a 125 and a Mercury Laser 19P, i would get 42-44 mph, so I am thinking you should be able to hit that. That was at 5800 rpm. Originally it had the factory alum on it (piece of S#$T) only got 39 at best out of it, so in my opinion SS is worth the cash.

Well I will tell you what i have. I have a 2005 1775 pro v with a 2006 150 optimax. I am currently running a 20 pitch enirtha ss. I am running 5600 rpms and with one person and 1/2 tank of gas I run 53 mph. Your speed doesn’t sound right. I know your boat is a little heavier but i have a kicker and really loaded down. Try a stainless.

...and stay with only Mercury aluminum for the testing until you find the right pitch. I'd start by asking for another aluminum 19- just in case the one you have is just plain labled wrong. If it still only turns 5200 at the point where porpoising starts, then drop to a 17 mercury aluminum to try next- which should increase your rpm to about 5500 or so. Normally I find the 150 Opti runs best propped to around 5500-5600 with a light load. You do not want to over-rev an Opti- the engine block and pistons don't mind, but the big compressor with all it's drive belts does not like to be over-revved. To carry the bow you should stick to SS props that are at least 14.25 diameter with a moderate to high rake- like the Merc Tempest Plus, and maybe the Enertia if it's 14.25 or larger in the pitch you need. But, on a rig in this speed range you probably will perform nearly as well with a plain old mercury aluminum prop.
Doug

I have a 2008 Alumacraft tournament 185 sport with a 2008 150 Optimax. After break in the best rpm I can manage is 5200 rpms wot with 1/2 tank of fuel and one person and normal fishing gear rigged. the motor mounted all the way down and trimmed out just below porpoise. Currently has 19 pitch Mercury aluminum prop. ( came rigged from dealer) runs about 43 mph. Tried a friends 17 pitch Michigan wheel aluminum and it would tach over 5800 wot. Runs about 38 mph. Tach is calibrated and I have digital tach readout on the smartcraft gauge and they read the same. I would like a stainless prop. Any suggestions? Any one out there with a similar rig? how is yours propped? Thanks for your response in advance. I do notice that I can't trim up much and the boat starts to porpoise. Can only get bow up so spray is about even with my console.

hiwayman,

I think a stainless prop would help your performance, maybe a 19 pitch Tempest Plus or Enertia.

But from reading about your other symptoms it sounds like you might have a hull problem where the bottom meets the transom. I've got a 2004 TS 185 w/200 HPDI Yamaha and T8 kicker and my boat was very sensitive to porpoise at every speed except wot. Also had a crazy looking spray coming off both sides of the big motor up about half way to the top cowling. I put up with it till this year but my dealer quit handling Alumacraft so I called Alumacraft customer service. Over the phone we pretty much decided the boat had a slight rocker (bottom bent up at the transom). They wanted me to bring the boat to the factory to adjust it but I live in South Central Missouri and the fuel expense plus a bunch of medical bills prevented me from doing so. I'd done a bunch of reading on how they do the adjustment which basically consists of driving a metal wedge between the transom and the bottom to bend the 3/8" or so of aluminum aft of the rear row of rivits down very slightly so I decided to do it myself. I used an old, dull cold chisel and CAUTIOUSLY wedged down about 1/16". It pretty much eliminated the mid range porpoising and completely eliminated the spray off the motor. It did move my spray line slightly forward.

I've said all the above just to explain my problem. If the factory had been closer I would have taken my boat there because it is a warranty issue. I'd recommend you talk to your dealer about the porpoising and low speed/rpm's because I suspect your boat needs a trip to the factory. The rocker and hook (bottom bent down at the transom) problems seem to happen occasionally in Alumacraft hulls. I don't understand why Alumacraft is still having the problem. But all in all I do love my rig and other than the hull rocker problem it has performed very well for me. Hope what I've said helps and keep us posted as to what you find out.

b2

Might want to have your motor raised up a hole or 2. I have a 2006 TS 175 with a 115opti mounted one hole up and I can get 5600-5700 rpm at 41mph gps with a 17p aluminum. I can't see you only getting 2mph more than myself with the 150. If I remember right your boat is only 5 inches longer than mine at 17'11" so that can't equate to much.

Check out the potential issue bumps2 says, but definitely don't even bother with testing any more alum props. That motor is made for SS props, and I will bet anything you will end up with a Tempest 19" after all is said and done, if you do your testing with several.

I would also try one of the newer 4 blade props from Merc (not the Trophy), and even a Hi-5 for the heck of it. But the Tempest is what you will end up with, is where I would put my money.

Good luck!

I would start by checking with other folks with a similar setup and see what hole the motor is mounted in. I would mount the motor as high as possible and this has a dramatic effect on porposing as well as holeshot.

I can tell you without hesitation that at sea level you shoud run a 19p Tempest or Enertia. At anything over 300' elevation, I would run a 17p "Enertia and not consider any other prop. I've been there and done that, tried most all of 'em, nothing compares to the Enertia on that combo.

I would not consider running any aluminum prop unless my main concern was rock damage to the lower unit.

Thanks every one. I'll try one thing at a time and the first will be a Merc. 17 pitch and another 19 pitch prop. in aluminum. I am only 50 miles from The factory, so the hook, rocker problem could be addressed at the factory. Will check into this also.