Dhadley, prop advice needed

[bmurray]

After searching and reading some older post I think you may be able to point me in the right direction on props. I don't want to start dropping money on just any prop. I have an 85 Charger with an 85 Johnson 150. Fully loaded will run 5500-5600 with a damaged (1 blade) factory OMC SS prop. I would like to increase top end performance, hole shots are not a question now, jumps right up. any recommendations? (raker, turbo, speed zone ect.) Also where should the engine height on this rig be set at? Right now I can run fully trimmed and could use more. Thanks for yours or anyones help.

 

[MGuckin]

Re: Dhadley, prop advice needed

You already have this topic started in another thread.<br />This should be posted in the non-repair section but....<br />Do a search on theoretical speed. <br />Hull with that motor is capable of 47-53 mph under ideal set up.(Not sure of hull factor to use or drive ratio). <br />Do a search on x-factor for motor height.<br />Decreasing prop pitch, while increasing top end speed, will result in slower hole shot.<br />Try having your prop repaired first.<br />Hope this helps. <br />Any other questions please continue this in the non-repair section.

 

[Dhadley]

Re: Dhadley, prop advice needed

Post a little more info about your set up. What exact prop are you running? It sounds like you could stand some more height with your existing prop. Is the motor mounted on the transom or to a jack plate? What's your water pressure now at WOT?<br /><br />Let us know!

 

[bmurray]

Re: Dhadley, prop advice needed

I was told it is an OMC SST prop. Not much performance from this prop at all. I was also told to get a jack plate on for fine tuning the motor height first, because this will probably increase WOT rpm's and then may require a larger pitch. Does this sound like a good idea? Thanks MG & Dhadley. Boat is already pushing speed well past what MG stated.

 

[Dhadley]

Re: Dhadley, prop advice needed

Let me ask again....EXACTLY what prop are you running? They have many SST props. A 15"...a 23"? We need to know what pitch you have in order to determine some kind of base line. Has the prop ever been rebuilt (look for numbers stamped on the outer hub)?<br /><br />A jack plate is a good idea. Proper X dimension depends largely on the prop. <br /><br />More info please!

 

[MGuckin]

Re: Dhadley, prop advice needed

Oops I entered wrong HP in formula. <br />Ballpark of 70 MPH. <br />He is spinning an OMC 21". Has it in his other post. <br />If he gets his "x" set, I think he could spin a 25" @ 5000?? Anymore might lose hole shot.<br />I used a factor of 200, ratio 1.85.

 

[bmurray]

Re: Dhadley, prop advice needed

Sorry all, my dumb mistake, MG was correct, it is a 14 1/4x21p. Don't think it has been rebuilt, here is the number(+389923) I have a few people leaning me towards a 22p raker and a CMC manual jack plate. I think I should put the CMC on first before buying the prop??? Right now hole shots fast, (have the SE sport fin on also) so I could deffinately give some up for more top end. Thanks MG and Dhadley for staying with me on this. (big investment to screw up)

 

[Dhadley]

Re: Dhadley, prop advice needed

A Raker has decent lift but there are others that have more. Get the jackplate first. Remember, and this is important, Make ONE change at a time. You will not only save money but in the long run you will save time and be safer.<br /><br />Good luck!

 

[bmurray]

Re: Dhadley, prop advice needed

Final questions on this post. Am I looking for the best speed/highest rpm combo when adjusting the plate, and where is a good starting point for the initial plate setting? I will let you know the rpm's for the correct prop sizing. Other than a raker, power tech???

 

[Dhadley]

Re: Dhadley, prop advice needed

The type of prop will dictate where the plate will be. A SST will run higher than an aluminum prop, a Raker higher than an SST, A Stiletto higher, a Turbo higher yet and a 4 blade higher than that.<br /><br />Install the jackplate so we can see what happens with your existing prop when you change the center of gravity (balance points, lift points or whatever you want to call it).<br /><br />Ther are many posts to come, youre just getting started.

 

[sho305]

Re: Dhadley, prop advice needed

I have a LaserII on my old Merc that seems to have good lift. I can trim it way high until it torque steers very bad and roosters good although alittle trim gives a rooster and best speed anyway. It is way better than a stock prop that will not trim at all without blowing, and the exhaust ports give a better holeshot to boot. The motor has been raised and the propshaft is maybe 4" below the vee bottom point. I get 2mph more with this 20p SS, but only run 100rpm more than a stock 21 aluminum. This newer type prop is bigger though. It is a 17' Checkmate & '73 150 Merc. Have to be careful as it will go real airborne on a wake when trimmed out around 52mph. Still lame for a 150hp.<br /><br />Remember: top speed requires a PERFECT prop, the sharper the better, and the correct rpm.

 

[bmurray]

Re: Dhadley, prop advice needed

If I have found good deals on the used props, please give me your recommendations. Thanks<br /><br />1) 22 OMC Raker<br />2) 22 OMC Turbo<br />3) 23 Renegade

 

[evin300]

Re: Dhadley, prop advice needed

ugghh, looks like its time to throw some money away.

 

[Dhadley]

Re: Dhadley, prop advice needed

Ditto Evin300.

 

[bmurray]

Re: Dhadley, prop advice needed

Ok, here is where I'm starting. CMC jack plate initial setting at 25". New PowerTech 14.25x23p prop. I will let youy know what happens. Thanks for everyones input.