walleyehed, or any of the prop guru's

[Rudy Brown]

This past week I was at Isaac Creek in Alabama fishing. I got the chance to play with my boat several days. I need yall guru's to help me out and tell me my next step. <br />Boat: 84 Cimmarron Bass Boat w/90 hp Evinrude OMC SS 13x19 prop. 24 gallons of fuel, ice chest and bait. Weight of boat ???. And just me.<br />Run 1: WOT 5400 rpms, trimmed all the way up(almost into tilt) little chine walking and 48 mph on GPS. Looked like the only thing in the water was lower unit. Kinda scary. When trimmed down to about 90% of max trim, speed was 47.3 and rpms went to 5250 or so, but no more chinewalk. <br />Run 2: same as above except wife and 2 kids with me. WOT 5000 rpms and GPS speed 43mph. Trim about 75%. Does these numbers sound about right?<br />At what trim level should I experence prop blow out? I can trim all the way till tilt and not get any blow out. A/V plate is about 1.5-2" above bottom of boat. Motor is in 2nd hole from top. Should I raise the motor 1 hole? <br />On a side note, I installed a "stingray" hydrafoil. It sure helped with the holeshot as now the bow dosent rise as much. I was able to trim the motor about 25% and take off. What was different was when I did that, as soon as the boat would plane, the motor would rev to 5000 or 5200 rpms for about 3-4 seconds then just accelerate like crazy. The rpms wouldnt drop, just the boat would accelerate. Havent had that happen before. Only happened when taking off with trim applied. I can tell you that when making a tight turn, the prop vents unless I trim all the way down. Thanks for yalls help. And Dhadley, them champion QL77JC's @ .040 did the trick. That 90 has never run so good. The hole shot is awesome.

 

[Dhadley]

Re: walleyehed, or any of the prop guru's

Sounds like you made some serious gains. Cool. <br /><br />Yes, we could try it higher. we can still use some extra r's. A little higher might - might - give us some extra lift.

 

[Texasmark]

Re: walleyehed, or any of the prop guru's

Hey D, sir, <br /><br />Would you happen to know the gear ratio on that engine and the WOT operating range?<br /><br />Thanks, <br /><br />Mark

 

[Rudy Brown]

Re: walleyehed, or any of the prop guru's

Originally posted by Texasmark:<br /> Hey D, sir, <br /><br />Would you happen to know the gear ratio on that engine and the WOT operating range?<br /><br />Thanks, <br /><br />Mark

I believe orignally the rpm range was 4500-5500 but I think 5800 is what I'm supposed to shoot for. And the gear ratio is 2.0:1 I think.<br />And I raised the motor up one hole last night. The A/V plate is now 2 1/2" above the keel. I'm gonna try it out later today or tomorrow. I'll be sure to post the results.

 

[Dhadley]

Re: walleyehed, or any of the prop guru's

Correct on the ratio & rpm.<br /><br />Anxious to hear how the height works out.

 

[Rudy Brown]

Re: walleyehed, or any of the prop guru's

I think I moved the motor 1 hole too many. I just got back from the river. Now WOT is 5200 but speed is 44 per my GPS. Vented badly with anymore than 40% trim. Run fine straight but even the slightest turn would cause venting and loss of water pressure. I'll move it back down 1 hole. <br /> On another note, I talked with a guy from 'The Prop Shop" who told me for about $45-60 he could re-pitch my SS prop to get more rpms. Is this a good idea? Or should I just get a 13X17 turbo 2?

 

[walleyehed]

Re: walleyehed, or any of the prop guru's

DO NOT repitch for higher RPM...that removes the efficiency from the prop...pounding the cup out is all that will be done...a NO-NO.<br />Let's hang tight and see what Dhadley has to add.<br />A 13-1/4X17 Turbo1 may be a good choice, and may allow that extra hole up....and yes, we have ways of eliminating water pressure issues.

 

[Rudy Brown]

Re: walleyehed, or any of the prop guru's

Thanks walleyehed for your responce. I've learned a lot from reading all the posts here. So far I've been able to vastly improve my hole shot.(vent holes drilled into prop) The boat now pins you in the seat when I nail the throttle. As a matter of fact, people who ride with me cant believe its only a 90! <br />As far as the water pressure goes, I noticed no difference when going straight, but turn either way, even slightly and I would lose 10psi(and you could actually feel the boat slow down and gain rpms). I was getting 25 psi at WOT. Before I moved the motor up 1 hole, I wasnt losing W/P when turning.(glad I got the W/P gauge now) Thanks again, Rudy.

 

[Rudy Brown]

Re: walleyehed, or any of the prop guru's

I guess since the first run was 5200 rpms or so @ just over 47mph and the run today was @ 5200 and 44mph, my prop is venting? Is this correct? Or is it just slipping more cause its out of the water more? Or are they the same thing? Seems to me it was more effecent lower. Just thinking out loud. I was really hoping for a big jump in rpms, guess not.

 

[Dhadley]

Re: walleyehed, or any of the prop guru's

Is this a Teleflex tach?

 

[Rudy Brown]

Re: walleyehed, or any of the prop guru's

Originally posted by Dhadley:<br /> Is this a Teleflex tach?

Oh no, Its a brand new Faria set to 6 poles. I just replaced the old tach less than 2 weeks ago and installed a water pressure gauge.

 

[Dhadley]

Re: walleyehed, or any of the prop guru's

Something doesnt add up. You changed the X dimension and the r's stayed the same - exactly the same - but the speed went down. <br /><br />It'd be interesting to check the tach against a known good shop tach. It wouldn't surprise me to find out the Faria won't go over 5200.

 

[Rudy Brown]

Re: walleyehed, or any of the prop guru's

I had it turning 5400 @ 48 mph last week. There was a little more chop yesterday. Would that make much of a difference? Should I wait till a calmer day and try it again?

 

[Dhadley]

Re: walleyehed, or any of the prop guru's

If there was enough chop to limit the trim, yes. A slight chop will, most times, allow for faster speeds. And therefore more rpm. Helps break the hull from the surface. Gets her "unglued" so to speak.

 

[Rudy Brown]

Re: walleyehed, or any of the prop guru's

Dhadley, I'm gonna leave the height alone right now and try another run later this week. The wind was blowin hard out of the south from a approaching cold front and it made the water very choppy and the ride rough. Weather supposed to be nice Wednesday. When I would trim past about 40%, I would hear the r's rise rapidly (I'm assuming venting, I could feel the boat quit pulling) but I would back off before looking at my tach. It would hold 5200 @ 25% trim @ 44 mph. What gets me was any amout of turning, I mean 1/8 of a turn of the steering wheel would cause loss of speed and higher r's. And my tach is graduated in 200 rpm increments. Its kinda hard to judge less than 100 rpms difference. How many r's should I expect to get raising my motor 3/4"? And thanks for taking time to help me with this. I know it can be taxing with so many dumb questions. Rudy.

 

[Rudy Brown]

Re: walleyehed, or any of the prop guru's

Dhadley, sorry about the time delay in posting. I took my boat out the other day and here's what happened. The r's were higher, 5600 at WOT, speed was 45mph as per my gps, but the prop was "venting" badly. The motor would rev freely but the speed was slow to rise. I mean I would be cruising @ 3500 and nail the throttle, the rpm's would jump to 5600 but you could tell the prop was slipping. Eventually it would grab and the speed would increase. But by that time I would come to a turn in the river and even the slightest movement in the wheel would cause the r's to rise but the boat to slow.(also it seemed like the boat wanted to slide in the turn. It never did that before) When I did have a straight shot at any distance, it would turn 5600-5800 w/ trim.(couldnt tell exactly while dodgin trees in the river, thanks to Ivan, Dennis and Katrina) On another note, I noticed that when the prop would slip, my water pressure would go down anywhere from 5-10 psi, for a total psi of about 15. It runs 25 @wot normally. Again, thanks for your help. Rudy.

 

[Ron G]

Re: walleyehed, or any of the prop guru's

Just wondering is the whale tail still on??

 

[Rudy Brown]

Re: walleyehed, or any of the prop guru's

Yep, its still on, but out of the water at WOT.