Prop and Trim question for 40hp 1972Johnson

[boatca]

--------------------------------------------------------------------------------<br />I have a prop with 3 fins, probably original type. Is there a certain replacement that is better for pulling the kids around on the tube skiis etc. type/place to get???<br /><br />Also the trim is a manually set and is set to the very last holes on the bracket underneath. Is there an optimmum place to set it. Boat does not flatten right out when towing a tube. Just need some info or direction as to setting it correctly<br /><br />Thankx in advance

 

[steelespike]

Re: Prop and Trim question for 40hp 1972Johnson

Its difficult to tell where your set up without<br />boat size and approximate weight,typical weight carried.would be really good to know engine rpm<br />at full throttle with one person.Also prop pitch.<br /> As far as motor trim If it is rocked all the way out (prop away from boat)the bow will tend to be higher and the boat will be slower to accelerate.<br />Rocked all the way in (Propeller closest to boat) the bow will stay down better maybe even to the point of plowing and acceleration will be quicker.<br />You need to try each notch for best performance.<br /> There is probably a setting that will work well<br />under most conditions but may need to be changed<br />for heavy loads usually rocked in for heavy loads.<br />Remember a little adjustment at a time.<br /> Weight distribution is important. Too much weight in the stern will make slow acceleration,<br />difficulty planing and a light bow,poor ride etc.<br /> It may be difficult but try to move the battery<br /> and gas tank forward even if only a few feet.<br /> If thats not possible just try to keep weight as even as possible.<br /> Good luck.

 

[suzukidave]

Re: Prop and Trim question for 40hp 1972Johnson

Steelspin's exactly right about the effect of the trim pin. You may have to move the pin in towards the transom when towing a tuber as against when normal running to improve your hole shot (ability to get up on plane quickly). If the trim pin is set all the way out I suspect it needs adjusting inward for regular running anyway unless it's on a very small boat or your transom is really raked. Try that first, one pin setting at a time, and you may not need a new prop for tubing. <br /><br />If adjusting the trim pin inward doesn't help then you can get a prop with a lower pitch for towing. This will make you get out of the water quicker, but reduce your overall top speed. Your existing prop should have stamped markings on it on the outside of the hub somewhere that read like 10x13 or something like that. The first number is diameter, the second is pitch. Take the prop off and, if you can't find the mark, take it to a Johnson dealer. You will want to drop only one or two inches of pitch and roughly same diamater if your boat performs well with the existing prop.<br /><br />One last thing, if you can its better to use a tachometer while doing all this. Your motor has a recommended WOT: (Wide open throttle) RPM range (does anyone know it for a 72 johnson 40?). Exceeding it can damage your motor. Changing props to a lower pitch and, to a lesser extent, moving trim pin settings into the hull both increase the maximum rpms your motor will achieve. <br /><br />good luck

 

[boatca]

Re: Prop and Trim question for 40hp 1972Johnson

You guys are the best.<br />I will try what you recomended and move the pin 1 step at a time and try it.<br /><br />As far as the boat goes it is a 1975 14' fiber glass deep V. Manufacturer is"Anchor" made in good ole Manitoba Canada.<br /><br />Will let you know what I find<br /><br />Boatca