Re: 1995 Baja Islander 188 25th Anniversary Edition
Hi Greg, thanks for the reply!
I believe I can help you out a little now. But first, the most important thing we need to know is your engine's WOT (wide open throttle) RPM when carrying your "normal" load. Take me for example, I almost always have my wife, two kids, and a 50 quart cooler with me and so I would need to check this with them in the boat too. The 350 Mag in my Baja is rated for a max WOT RPM of 4600 and I would think yours is the same. The only reason for you to buy a higher pitch prop would be if your WOT RPM is HIGHER than 4600. If not, your RPM will drop too low with a 23P prop and you will bog your engine down and overheat it. If your engines WOT RPM is 300 to 400 RPM lower than your rated WOT RPM, then you need to step down one size. Changing from a 19P to a 17P will raise your WOT RPM 300 to 400 RPM and changing from a 19P to a 21P will lower your WOT RPM 300 to 400. Keep your WOT RPM within 100 RPM of your max WOT RPM rating, while carrying your normal load and with the motor trimmed just under the point where the boat begins to porpoise, will give your boat the best holeshot, highest speed, and best fuel mileage too. It will also give you the extra little bit of power to carry a little more weight, like and extra couple of passengers, and still be able to easily pull a tube or skier.
I found this out the hard way. My Starcraft which is the family fishing rig and the boat in a my avatar pic, came with a 21 pitch aluminum prop. It has a 4.3 and Alpha 1 drive. With the four of us and our cooler, on smooth water, it ran 49 mph on gps, turning 4200 RPM. The WOT RPM of that motor is 4200 to 4800. I got excited, and with the help of Capt. Morgan
got on the internet and ordered a brand new 23P 3-blade Stiletto thinking I was going to hit 60 in the old recycled beer can. I was very wrong! The boats top speed dropped to below 40 mph and the WOT RPM dropped to 3800 and the engine started to overheat if I ran it wide open for any amount of time. From what I gather, when you drop the WOT RPM too low, the impeller in the drive don't pump enough water to keep the engine cool under the load its seeing. To make matters worse, I added a Stingray whale tale to please the wife, it does allowed the boat to plane at a much lower speed, but it cost me about 6 or 7 MPH on top end even when I switched back to the 21P aluminum prop that came with the boat.
To really further the issue I added a large trolling motor and its 3 batteries in the bow. :facepalm: So, I bought a 19P aluminum prop and it got me back up to 40 MPH, but my WOT RPM are still on the low side. So after I grenade this prop on a rock in the river where we fish, I will have to to go with a 17P to try to get as much speed and power back as I can. The river is full of fish but also full of prop hazards too, so I will keep an aluminum prop on it from now on to keep from tearing up the outdrive. Something else I learned after I bought the 23P Stiletto, when you change from a run of the mill aluminum prop to a stainless high performance one, you need to DROP two pitch numbers to get the same performance. So if this is true, if I where to remove the trolling motor and its batteries, and that %$#& whale tale, a 19P stainless prop would be about the same as the 21P aluminum.
Your Baja might be able to turn a 23P stainless prop if you strip all weight out of the boat except you and your life vest and about 5 gallons of gas, but I'd be willing to bet that it would go faster (with the same light load) with a 21P one.
I hope that you can learn from my mistake and once we know your WOT RPM under normal load, we can get you headed in the right direction. If you don't want to take my advice, then I will make you a great deal on a 23P stainless Stiletto that has only been used ONCE!....LOL!
I keep threatening my wife (whom if it were up to her, none of our boats would ever go faster than about 25 mph.) with adding enough horse power to our Baja so that it would be able to turn that 23P Stiletto and we'll see if it can hit 80 and well, I would probably get thrown out of the forums for good if I posted her actual reply!...LOL!!
