More prop results. and boy are they confusing me.

[budsbud66]

Ok... for all of you who havnt been following me.<br />1996 16.5 fiberglass starcraft tiller ( STERN HEAVY)<br />1984 65hp comm evinrude (transom rating maxed)<br />all results are tested in alike circumstances.<br /><br />Results 1 OMC 13 3/4 x 15 aluminum<br />30mph @ 5800 RPM's (fair hole shot)<br /><br />Results 2 OMC 13 3/8 x 17 aluminum<br />32mph @ 5900 max RPM'S (poor hole shot)<br /><br />Results 3 SST II (used) 13 3/8 x 15 Stainless<br />32mph @ 6200 RPMS (over limiter) very good hole shot<br /><br />Results 4 SST II (NEW!) 13 3/8 x 17 stainless<br />33.5mph @ 6100 RPMS ( this prop has drilled vent holes and provides a fair hole shot.) excellent mid range acceleration.<br /><br /><br />My confusing starts with. i thought im suppose to lose rpms when going to stainless? im gaining way over my max rec rpms.<br /><br />The rule should go that i should move up to a 19 pitch prop.. but i will have virtualy no hole shot. The boat is very stern heavy and does not make it on its pad. ever. <br /><br />Should i look for a 17 pitch prop that will lower my max RPM's? or go to a 19pitch + trim tabs ? <br /><br />any recommendations will be appriceated...

 

[budsbud66]

Re: More prop results. and boy are they confusing me.

Oh yah more thing that i have been contemplated.. perhaps i should move up to a 14 inch diameter.. will just fit on my motor. right now the 13 3/8 is a bit small.

 

[Dhadley]

Re: More prop results. and boy are they confusing me.

Seems OK to me. Not unusual at all. With the stainless you can trim it out further to reduce drag or even if it's at exactly the same trim angle the ss prop has less blade flex which gives more lift and again, less drag. Obviously your hull has responded and responded quite well. <br /><br />And remember the used 15 SST II was worn enough the cup was gone from the tip.

 

[budsbud66]

Re: More prop results. and boy are they confusing me.

should i try a good 19 pitch thats well ventilated.. i may be able to top it out around 5900 rpms which would be ideal. and if it does plane well ill add trim tabs.. i dont hink 35mph would be unreal in that setup.. but it will cost me 350$ :/ thats alot to bet on..