Get up on pad

[boaterntexas]

I have a 17.5' fiberglass bass boat witha 1976 115 hp merc on it, after reading some earlier post on this site I believe that my problem with hole shot and top end speed is that I'm not gettign on the "pad". The motor is about 2" too high on the boat, but I now don't think that is the problem, I have noticed that sometimes the boat will lean to the driver (starboard ?) side when on the trailer, if this happen we will realnd it and get it back in order, I doubt the previous owner ever did so, I have also notice that there is more whieght on the driver side of the boat, the driver, the console, the battery, tackle, and trim motor are all on that side of the boat near the rear. I can trim the motor up to where it is cavatating, and I can trim it to where the boat will "bounce" or jump, but it never seems to get on the "pad" ( i'm assuming this is the extension of the hole, near the tarnsome. same as planing?) so I guess I neeed a new prop with more lift ( raker?) are my assumption ignorant, or on the right track.? I'm currently runnig a 21p prop which I was told has been worked, I think they took some of the negative edge ( inward curve?) off the top of each blade? Not sure what that means.. so Should I chage pitch, or just go to a raker, or cupped prop. ?? added info, at wot I can peg over 6g's of rpms, I knwo I need to get this down, but I run heavey loads sometimes (brothers)my speedo which I don't think is good typically will read about 38 mphs at WOT with one person on the boat, there is a good and steady chage of water pressure all the way up till about 35 mph on the spedo, 5600 rpm after that the spedo chage is almost none, I can give the motor more throttel and get rpms up and past 6000 but the spee ( water pressure) doesn't seem to cahnge<br /><br /> Thank, sorry so long wided, its a boring day at work with little to nothign to do but sit and day dream about being on the lake<br /><br />Thomas

 

[Dhadley]

Re: Get up on pad

Something is way off here. 6000 rpm and a 21" prop at 38 mph is over 40% slip. <br /><br />First get an accurate speed reading. GPS - measured distance etc. Verify the tach setting and readout.<br /><br />The pad is a flat area on the keel (center). It looks like a ski. Your boat may not have a pad, simply a V. If your boat has a cut out area in the back (I think thats what you were describing) thats known as the step or notched transom. If you have a step most likely you have a pad. The other flat areas on either side of the keel are lifting strakes.<br /><br />You are probably right - you need a prop with lift. If someone flattened out the tips of the blade it probably wont have any lift at all. <br /><br />Lets verify some things and go from there. <br /><br />Good luck!

 

[boaterntexas]

Re: Get up on pad

thanks for your help. I do have a cutaway, and I'm sure it is flat, not "v" assuming that my my tach and seepdo are correct, what else could cuase that much slippage, I have rehubbed the prop, but if look look straight down unto the prop the hub seems to be off center a tad, not sure if this is typical or possibly a problem. I have noticed somethign that sounds and appears to be slipping if I try to do a quick u-turn, once it starts to slip I I have to bring th motor all the way back down to idle then go again, this is the only time I have "heard" slippage.<br /> If I don't have access or capital for a gps, is there any other way to test the speedo?<br /> If the cav plate comes to the surface of the water, is lift still the issure?<br /><br /> Thanks, <br /> Thomas

 

[Dhadley]

Re: Get up on pad

It just sounds like your prop doesnt have much "bite". The tips of the blade are very important so if someone has removed cup fron this area or laid back the blades that mamy be causing the slipping. <br /><br />Ok lets not worry about the accuracy of the speedo for the moment. Try props from friends and just compare the rpm, speed (on your gauge - accurate or not we are only looking for differences) and feel. <br /><br />Take note of where the water comes off your hull. Try another prop and see where the water breaks. The further back means there is more hull out of the water. Thats what you are looking for - reducing the wetted surface to reduce drag or resistance.<br /><br />Good luck!

 

[G DANE]

Re: Get up on pad

Hi Boaterntexas<br /><br />Are U sure your tach is set correct ? Did you install it yourselves, or previous owner. Have you aways had that much slip ?

 

[boaterntexas]

Re: Get up on pad

recently just bought the boat,, I have no history on it, but It really does sound what I would expect 6000 rpms to sound like. Why would some one take the leade edge off of this prop on this rig? I do know that after I took off the fin that was on the cav plate, the water line did move back a bit, top end seem to improve, although the speedo did not reflect it, and hole shot was a tad bit better.. <br /><br /> Thanks again

 

[boaterntexas]

Re: Get up on pad

Checked the boat out, it definitly has a pad, had the prop looked over again, and was told it "shouldn't be cuasing the problem" look at another boat by the same manufacture "hydrasports" in the same year class (1976) and its cav plat was high up on the pad also more than the 2" mine is, is this a manufacture or dealer fualt.<br /> assuming the prop is not the cuase, could the uneven whieght disurbution be the cuase, I would say at any given time the driver side of the boat carries about 30 - 50 lbs more than the passenger side.<br /> Is there any room of concern for the operations of the motor, or just the rig it self?<br /><br /> Thanks,<br /> Thomas