Can I go faster?

[Flames]

Hello all, I have a 13 3/4 X 15 pitch OE prop on my boat and wondering if a 17 pitch would make it any faster.<br /><br />If Im on by myself it will do 4200 rpm @ about 40 mph if I trim it out.<br /><br />I dont think I should turn anymore rpm's but I just currious if I can go any faster with this 3.0,4cyl.<br /><br />As always, Thanks, Rudy

 

[dcpcccrc]

Re: Can I go faster?

if your hitting 40 mph with it that sounds like the motor runs great changing the prop may not make you go faster but it might make you do 40 at less rpms

 

[tommays]

Re: Can I go faster?

your allready on the low side for wot at 4200 rpm any bigger prop will lower your speed and rpm and may cause engine damage due to engine lugging <br /><br />a smaller prop would give you better acc but may give to high a wot you can only find out by trying<br />your motor plate should list a wot ??? about 4600 rpm<br /><br />40 mph is prety good speed for a 3.0<br /><br />tommays

 

[achris]

Re: Can I go faster?

When you're near or at WOT it then becomes a matter of numbers. <br /><br />You have a boat weighing X lbs and a motor producing Y hp, and Y hp will push X lbs of boat at Z mph. For more speed you need to do one of 2 things. Decrease X or increase Y. <br /><br />The only way to get the best speed for a given combination is to find a prop that is of maximum efficiency that allows the engine to run at the rpm that produces that maximum horsepower. <br /><br />As stated earlier, you are at the low end on the rev range. The engine is speced 4200-4600 rpm. Maximum horsepower will be produced at 4400rpm. By running the 15" pitch prop the engine is not quite producing max hp. If you put a 13" prop on you'll probably find that the engine will spin up to about 4500 rpm with a couple of people on board and you won't have to trim up so far. Not only will you then be producing max hp, but your engine will thank you with less fuel consumed, better acceleration and it'll last longer, as will the gear oil.<br /><br />Chris............

 

[Flames]

Re: Can I go faster?

Thank you all for your input.<br /><br /><br />What would be a good way to make more hp with this little 4 cyl?<br /><br />Thanks again

 

[xltier]

Re: Can I go faster?

there is no replacement for displacement!

 

[Boatist]

Re: Can I go faster?

Only way to make more horse power really is to get a bigger engine. The 15 pitch you have is a good prop for that boat. You could go to a 13 pitch and turn 4600 rpms but you will be about 3 mph slower and use more fuel. Your hole shot would be better with the 13 pitch. If the 15 turns 4200 with your heavy load then I would stay with that prop but if that is with your light load then a 13 pitch would be better for your heavy loads. If the prop is aluminum then you may gain about 1 mph with a stainless steel prop of the same pitch.

 

[affa]

Re: Can I go faster?

Hi Flames

 

[affa]

Re: Can I go faster?

Hi Flames<br />I have the same boat as you with a merc 140 and alphaOne outdrive, my gear ratio is 1:84, <br />I thin the original is 1:98.<br />I use a 14,8x19 prop on mine, and it works fine, my instrument shows 40 mph, but my gps says 34 at 4200rpm.<br />Regards<br />Affa

 

[Flames]

Re: Can I go faster?

Thanks again everyone,<br /><br />I guess I will just get another boat, one with MORE horsepower.<br /><br /><br />Thanks, Rudy