I want more power

[jagreenall]

I have a 1991 17' Bayliner Capri with a 70hp Force outboard. I use the boat to mainly pull the kids around on a tube and skis, but when I (only 160 pounds) tried to get up on a single ski it did not have enough power to get me up. Is there aything I can do to the boat to help? I read through all the other forum questions and came up with 3 possible solutions. 1)I do have those plastic fin stabelizers things on the engine and somewhere it sounded like those could be slowing me down. Is this true? 2)I was wondereing if a new prop would help. If so what should I go with? 3)I was also wondering about the pitch. The pitch is all manual, so I have just been putting it so it looks level with the hull. What do you think? Any other ideas to help get the extra umph I need to pull an adult skier out of the water on a single ski? I can get it up to 35 mph, but just need the extra power off the start.

 

[turtle1173]

Re: I want more power

I don't have any information to help you but I do know that for someone to help, they will need to know how many RPM's you are running at WOT. Also we need to know what prop you are currently running.<br /><br />Shane

 

[jagreenall]

Re: I want more power

I am assuming it has the original prop on it. The engine runs great, but I have no idea at what RPM. I just "hit it" and go. Like I said it can get up to 35mph, but starts out too slow to pull a single ski.

 

[roscoe]

Re: I want more power

What you are referring to as "pitch" is actually the trim. The angle of the motor, to the boat. Pitch is actually a measurement of the prop, referring to the angle of the blades.<br /><br />You might try trimming the motor back a notch or two. It will not solve your skiing problem, but may help overall performance.<br /><br />Your current prop may be a 10 3/8 inch diameter, by 15 pitch, or there about.<br /><br />If you examine the prop, you should find a number similar to this "48-73140 A40"<br /><br />You may have to remove the prop to look at the inside of it.<br /><br />Post the number you find on your prop.<br /><br />If you drop the pitch down an inch or two, from where you are, you will get more pulling power. But you must be careful that your engine does not over rev, above the recommended rpm's. Your recommended rpm are 4750 - 5250. You will also sacrifice some of your speed, maybe 2-3 mph.<br /><br />Once we know the prop you are running, we can recommend a new one. The actually sell a decent aluminum prop here on iboats. Its a Hustler prop by Turning Point. Thats what I run on my '95 70 hp Force. Only $91.<br /><br /> http://www.iboats.com/mall/index.cgi?prod_id=1482

 

[steelespike]

Re: I want more power

If you trim the motor in,prop closer to the boat,<br />for sking it will get up quicker but your top speed may be reduced.If you trim out it will<br />be slower to get up but top speed may be higher.<br /> You really need a tach.Tiny Tach has a web site<br />very easy to install and about $40.<br /> You really need to know your present rpm.

 

[Spidybot]

Re: I want more power

You may also have to accept, that 70hp on a 17' will not be sufficient to both push the boat, pull a single-skier, carry persons and load and run great top end under all conditions.<br /><br />The power/weight ratio is important and you should make sure you carry only the neccessary weight when power for skiing is needed.

 

[jagreenall]

Re: I want more power

The prop is 48 816706 A40 14P. I am guessing the 14P is the pitch, but what do the other numbers mean? I have a tach on the boat but have never paid much attention to it. I will check it out tomorrow when we got out one last time before school starts. Any comments on the stabelizer fin thing?

 

[roscoe]

Re: I want more power

You have an actual Mercury prop. It is a 14 inch pitch. The other numbers refer to hub size and such, all in code of course.<br /><br />The stabilizer fin, is probably helping your holeshot already. <br /><br />If you drop the pitch to 13", your rpm should increase by about 200, and so on.<br /><br />If your rpm are already at 5200, with a light load in the boat, just cruising, then a prop change is not a good idea.<br /><br />Where is your anti-ventilation plate, in respect to the bottom of the transom?

 

[jagreenall]

Re: I want more power

The top of the anti-ventelation plate is just under the bottom of the boat by about 3/4 of an inch it looks like with the motor in the down position. It looks as if it has not been tampered with and is as it came from the factory. I also just noticed that I have been running with my trim as forward as I can get it. I have 3 or 4 holes that an adjustable shaft slides through that lets me adjust the trim and I am allready in the closest one to the boat.

 

[jagreenall]

Re: I want more power

Ok, after a fun day of boating, here is what I have learned. The RPM at WOT is 4900. I was getting a top speed of 33mph today with 3 in the boat (2 being teenagers). My current prop is not in the best of shape, but is not too bad as it has a few small dings. My current prop is 10 1/2" diameter with a 14 pitch. Go ahead a tell me what you think.

 

[The Marine Doctor]

Re: I want more power

Looks like you can drop down to a 12 pitch. More power...and possibly more speed as you will be using more RPM.<br /><br />TMD

 

[jagreenall]

Re: I want more power

Mercury says that the recomended rpm's are 4750-5250. The Force book I have says it is 4500-5500. If I am currently at 4900 rpm's and am using a 14 pitch, a 13 pitch would take me to 5100 rpm's and a 12 pitch would take me to 5300 which is over the Mercury recomendation. I was also told that while pulling a skier my RPM's would be less and if I went with a 12 to just watch my RPM's at full out speeds. I am currently using the original prop which is 10 3/8" X 14 pitch. I found an article that said the 50hp on my boat pulled up a 210 pound skier. What should I do?<br /><br /> http://www.goboatingamerica.com/main/article.asp?id=468

 

[roscoe]

Re: I want more power

I have serious reservations about the info in that "article." Sure sounds like an advertisement.<br /><br />They don't say what pitch the prop was, or if the skier was pulled up on one or two skis.<br /><br />And a 50 hp pushing a 17' glass bowrider that fast is pushing it.<br /><br />What should you do?<br />Do a thorough decarb on your engine.<br />Buy a 12" pitch prop to give yourself some pulling power.<br />Keep an eye on your tach.

 

[jagreenall]

Re: I want more power

I did the de-carb and got the prop in the mail today. I will install it, but will have to wait for a little while to take it out and test it. I hope it will all do the trick. Thanks to all of you for your help. I will let you know the results. PS: any secret tips on installing the prop before I just follow the directions that came with it?