Prop change on a 1986 175hp Black Max

[KCLOST]

Now currently this motor is rigged with a 25p 3-blade Lazer... It runs pretty good especially since it is pushing a Ranger 371V 18ft bass boat...<br /><br />My current rpms at WOT are 6000 when the motor is tilted out to the max... The hole shot is good...<br /><br />My question is what whould be a good comparison between the 25P 3-blade lazer and a 26P 4-blade Trophy? <br />Higher pitch obviously on the Trophy, but lower overall diameter....<br /><br />I'm going to try it out, but wanted your thoughts also..<br />Thanks

 

[LubeDude]

Re: Prop change on a 1986 175hp Black Max

All you can do is to try it. Being a bit smaller diameter may not make much difference in your hook-up at full trim as you have another blade. Im going to say that it will be about a wash in speed but you will lose about 200 RPM at WOT.<br /><br />What do I win if Im right?

 

[Ron G]

Re: Prop change on a 1986 175hp Black Max

Give it a try,you may be able to raise the motor up a little more which will help alot.test it and give us some numbers to look at,theres one thing ive learned 3 or 4 blades react different on each type hull and how much you move the motor up or down.are you blowing out at all?and you said you can trim all the way?

 

[KCLOST]

Re: Prop change on a 1986 175hp Black Max

Not blowing out... I'm can trim out as much as I want to Ron (almost to the max anyway)... If I go out much further I will start to loose water pressure but still do not blow out... So I don't think raising the motor is an option due to the water pressure issue...

 

[Ron G]

Re: Prop change on a 1986 175hp Black Max

Sure dont want to loose water preassure,this thread got me wondering yesterday so i put my 4 blade back on and raised my motor another 1/2 inch,on my hull the 4 blade can not hold a light to the 3 blade which i already knew but was wanting to test it up even higher.try to borrow a 4 blade and see first,you may ended up looseing rather then gaining.

 

[KCLOST]

Re: Prop change on a 1986 175hp Black Max

That's what I'm going to do Ron, I can try this prop out first before buying...

 

[KCLOST]

Re: Prop change on a 1986 175hp Black Max

Well I tried the 26P Trophy out today, and it just really lugged the motor more than I like...<br /><br />Ran about the same top end speed 62mph, but only got up to 5100-5200rpms... Hole shot was slower, noticeably slower but manageable...<br /><br />I'm surprised that I'm loosing 700 rpm with this prop... But thats what happened...<br /><br />Bow lift was better however.

 

[Ron G]

Re: Prop change on a 1986 175hp Black Max

i was afraid that was going to happen,i dont loose that many rpms with mine but i lost 10 mph and no bow lift,for some reason my 4 blade likes to run lower in the water.How was your water preassure with the 4 blade?

 

[WillyBWright]

Re: Prop change on a 1986 175hp Black Max

I can help with that high mounting water pressure issue. If you have water intake holes that are part of the gearcase casting (others have plastic intakes), you can thread the upper three sets of holes and plug them with stainless setscrews and red loctite. Start with the top and work your way down (experiment). 1 or two pairs, no problem. The third starts to make me nervous. NOT to 4!

 

[KCLOST]

Re: Prop change on a 1986 175hp Black Max

I've heard of that Willy, But is there any chance of starving the engine of water at idle or no-wake speeds? My engine already reaches 180-210F (metal head temps) at those rpm levels...<br /><br />Ron, <br />I did not notice any difference in the water pressure... Still holding around 20-22 psi at WOT...

 

[walleyehed]

Re: Prop change on a 1986 175hp Black Max

That 26 4-bld is like swinging a 27P 3-bld.<br />Losing 700RPM tells me it's not suiting the hulls needs and it may be just too much for that engine to make it work right-not enough HP to utilize the design.<br />Diameter, as you now know, can fool ya..if ya can't raise the engine enough to find how high it will run, you're flat limited.