Prop for speed ?

[tjstrike]

I have a 17'6" 1985 Bayliner w/ a AQ125A volvo penta. The prop is marked Michigan 2028, the boat has a top speed of about 35 mph, I would like to get about 10-20 mph more speed without damaging anything. Can I do this with a different prop and what size should I get ? Thanks for the help, Troy

 

[frankie jr]

Re: Prop for speed ?

An extra 10-20 mph is alot to ask. your prop should have another number # on it it will be:<br />-----x15 for example this means you have a 15" prop. To go faster you should go to a higher # pitch, if your engine is peaking out at full throttle. The 15" means this prop will move 15" through the water for every revolution. Prop sizes vary from 11" or less to 29" or more be gentle a little goes a long way and you can loose a lot of power with the wrong prop. Good luck.

 

[Gary H NC]

Re: Prop for speed ?

An extra 10 to 20 mph won't happen with a prop change..<br />Maybe 5 mph if your lucky.<br />Find out what your max rpm is for your engine then start thinking about a prop change..<br /><br />Welcome aboard Bay Bay and Frankie!

 

[Silvertip]

Re: Prop for speed ?

Put another way, if your boat were capable of another 20 MPH the manufacturer or the selling dealer would have installed a prop to accomplish that. Make a wide open throttle run with a normal load and note the engine RPM and speed. If the engine is not reaching its recommended WOT RPM it's already overpropped and increasing pitch will likely slow you down rather than speed up. Remember also that a boat has no transmission so increasing pitch to "theoretically" get more speed means you sacrifice hole shot. So if the boat struggles to get on plane now, it will be worse with a higher pitch prop. If you also tow tubes, ski, etc., more pitch will make the boat less versatile. Make sure the engine is performing as it should. You might find that Nauticus Smart-Tabs (trim tabs) will gain speed and enhance boat performance for half the price of a new prop. These forums are full of reports from people that have them and would not be without them. I'm one of them.

 

[wvit100]

Re: Prop for speed ?

Your motor can only produce so much torque. Torque is the power that twists the transmission and the prop. If the prop has too much grab in the water then the motor won't be able to turn it at the proper rpm because it would take more torque than the motor can produce. Trying to turn a prop with to much bite in the water puts lots of stress on the engine and transmission parts until something has to give. It's like trying to pull heavy trailer with a Honda Accord, either the transmission or the motor's going to go.

 

[tjstrike]

Re: Prop for speed ?

I will do the mph vs. rpm test and reply back, I'm new to boating and the guy I bought the boat from said that there was a speed prop that I could put on the boat to get it to go faster, I'm not even sure that this prop is the stock prop, the boat is 21 years old but thanks to all for the imput. Troy

 

[walleyehed]

Re: Prop for speed ?

For a boat of that size, it takes 17HP to gain 1MPH...now, this can change with a more efficient prop, but not much.<br />You're limited with heigth with a sterndrive, so 3MPH would be the most I would ever expect to gain, unless you have a prop that is WAY off now...Good Luck.

 

[cm5408]

Re: Prop for speed ?

i have an easy way for you to gain 10 - 20 mph...take out the 120hp 4 cylinder and replace it with a small block, you should have the room to sit a 305 or 350 in there. That should do it.

On a serious note, unfortunatly bayliner in the past (and still in the present) under power their boats from the get go. To offen they were able to reduce the price of their boats by using a smaller motor. All this ever did was get a boater excited about buying a boat at a lower cost, and then once they got it on the lake, it just made them mad with the lack of performance. Now this is not a knock at bayliner. I had a 17 ft arrow glass with a 120 merc. Alot of boats that size and that old had four cylinders in them. In the mid 90's the boating manufactures started using 4.3l v6's insted (just like they do now by glastron, maxim etc). my lil ol arrow glass would have performed a ton better with 160 in it. On a different note the 180hp inline four cylinder (merc) that is in my buddys 19 ft galaxy (1981) performes awesome!! shame there arent more of those motors around...