Prop help....

We are having an issue with a 1992 692 Ranger Fisherman with 1992 Mariner 150 Magnum 3. It has a five blade mercury high 5 ss prop (don't know the pitch) which we are hoping is the problem. We checked out the motor and changed everything from plugs to fuel filters. All 6 cyl are 108-110 on compression tester. With two guys, 4 batteries and 9.9 kicker it takes atleast a minute to get above 10mph. 0nce it hits 15mph (if wind is in ur face u wont get on plane) it will plane out and trimmed up runs 38 mph at 4000 rpm tops. We were on Erie 2 weeks ago and coming back into the wind/waves we couldn't get over 10 mph and couldn't get on plane with 3 guys. The only thing we are thinking it could be is the prop. Is there anyone on here that could help us out on which prop this boat would run hard with? Manual says motor should be running at 5-5600 rpms. Thanks guys!!!

anzomcik lol! Bar2 is my cousin and we are talking about the same boat. I made a new post now that we narrowed our problem to the prop. I was hoping to have the prop pitch # tonite but my cuz's fiance had the collar a little tight on him today so he didnt have time. Lol! Thanks again!

Ok 20 pitch ss 5blade.
rule of thumb is for each extra blade subtract 200 rpm, so if you remove 1 blade you add 200 rpm.
So if you had a 3 blade ss prop you should be in the ball park of 4500rpm.
 
If you go from Alum. prop to SS you subrtarct 200 rpm (another rule of thumb) So going from SS to Alum you add 200 rpm.
So if you had an Alum three blade prop in 20 pitch you would be 4700 rpm (remember its all rule of thumbs, nothing is in stone)
 
Each inch of pitch increase is 200rpm decrease, because it is more aggressive. (another rule of thumb)
So by decreaseing your pitch (less agressive) you will add 200 rpm for each inch of pitch.
 
So if we shot for that 17P i guess in my first post, you will be decreasing by 3" so you add 600RPM, that would bring you to 5300rpm Give or take.
 
I posted a link of a prop I think would be good for your set up, You must understand a 17 pitch prop from one brand isnt the same as 17p from another brand and with the differences in hull designs nothing is a perfect exact prediction. I want to make it clear with prop there is no perfect garrentee that my rule of thumb math will be exact, but itis the best starting point I think most can agree on.
 
Also the prop I linked is a four blade, and i said earlier adding a blade will decrease 200rpm and i did not do that in my math. Reason why is i am very fimiliar with this family of props, With all the props I have run I have not seen a noticible decrease in RPM with this four blade. So this is a prime example of where the rule doesnt fit.
 
I think this would be a very good in the ball park prop for your rig. Props are not returnable in most cases. Once you buy it its yours, thats why you see many on ebay or craigslist with very little use. If this is somthing your going to order please double check i put in your motor information correctly, and it is a 14.5 dia prop and your current prop is 12.75 make sure you have the 1 inch clearence right now between your antivent plate and the prop blade (so it can clear and not hit) I believe you should have that clearence but it never hurts to check. 
 
http://boatpropellers.iboats.com/Mariner/150_HP_(1978Newer)_17.00-Pitch_Amita_1513-145-17_Propeller/309/7393/?cart_id=745706483