prop pitch johnson 150 1999

[phoenixgold2100]

Hi guys I have a stratos 17 foot 273 with a Johnson 150 24 x14.5 raker first gen prop and I can only get 5100 rpm 60mph.

I am wanting more top end and somewhere around 5800 rpm.

I have a chance to pick up a 4 blade 25 pitch 13" prop.

My question is will this prop give me more rpm and speed?

If not what prop should I be looking for.

 

[Chris1956]

Re: prop pitch johnson 150 1999

No, you need to drop pitch to gain RPM. You may lose speed, or you may not, depending on the power band of the motor and the friction of the hull. In general a 2" pitch drop will gain you 400 RPM. If the power increases at that increased RPM, you may get a bit more RPM gain that that.

 

[SkiDad]

Re: prop pitch johnson 150 1999

I'm not sure you can get any more speed at this point - but a 21 or 22 pitch should get your close to what you want RPM wise. I think your speed will not be faster but will be about the same. I'm calculating around 59-61 mph

 

[phoenixgold2100]

Re: prop pitch johnson 150 1999

thanks for the replies. I have seen guys hitting 71mph gps with this same hull and engine but I cannot get mine past 60.

Would the speed not increase with higher rpm?

There are guys on this forum that rip their looper v6 at 6000 rpm all day long. I can't get past 5100 with the jack plate all the way down.

If I raise the engine I do not get any bow lift with this prop

 

[steelespike]

Re: prop pitch johnson 150 1999

Prop calculator indicates about 4% slip possible but unusual. 8 - 12% is more typical.. I believe it develops it power at 5000 rpm. I think typical range would be 4500 to 5500.At 71 mph 24" prop and a more normal slip of 8% you would be turning about 6300 rpm.What size and model prop are these guys running.Is your 60 by gps?You may want to be sure the motor is in excellent tune w good compression.
You may want to verify the tach is accurate.If you are losing bow lift at a higher setting your either too high or need a different prop.

 

[phoenixgold2100]

Re: prop pitch johnson 150 1999

I have talked to one guy on you tube saying his boat does 68-70 all day with a worked first gen raker same pitch and diameter as mine. I have gps mine and have only ever got it to 60 with just me and low fuel. I have tried the engine at several different heights and when the engine is up I have zero bow lift and it loses speed. currently I am at 5.5 to 6" below the pad. This seems way deep to me but this is the only way I can get the bow out of the lake and the boat on the pad. My engine is a fresh rebuild with 110 pounds in all 6 cylinders. as for my tach I assume it works as it goes to 5100 rpm everytime. I am shopping for a new prop I am just not sure what one to get for the most top end and bow lift possible. I have to believe this engine will make a more power at a higher rpm but maybe 60 is the best I can do with a 150.

 

[steelespike]

Re: prop pitch johnson 150 1999

If your struggling to get bow lift maybe you should check the bottom with a straight edge. May have a slight hook.
I don't know the typical 150 motor compression but 110 seems a little low for a fresh rebuild. 100 is usually the rule of thumb minimum on a used motor.
As I understand it as a 2 stroke motor goes beyond the designed rpm max; hp production degrades.
The guy getting 70 mph If we assume the reworked prop is like a 25" 8% slip nets about 5946 rpm.
At this point it appears a similar reworked prop would probably lower your rpm.
You might ask him about his height and compression.
Don't assume everything is right because its a fresh rebuild.
Check the timing,throttle opening all the way,correct spark plugs.
operating temperature.

 

[metriccrescentwrench]

Re: prop pitch johnson 150 1999

thanks for the replies. I have seen guys hitting 71mph gps with this same hull and engine but I cannot get mine past 60.

If you believe them (not so sure I do) then find out what prop they've got and how high they're running it.

And if nothing else go to a lower pitched prop so you can get to the upper end of your engine's max rpm range. The engine will be happier and you'll have a better hole shot.

 

[jestor68]

Re: prop pitch johnson 150 1999

Typical performance of a 17-18 ft bass boat powered by a stock 150 is 60-62 mph.

The guy that claims 70 mph is not telling the whole story. Like he's hiding a 200-225 power head under that 150 cowling on a stripped down Bullet.

 

[jestor68]

Re: prop pitch johnson 150 1999

My engine is a fresh rebuild with 110 pounds in all 6 cylinders.

140-150 would be "like new" compression numbers, with 110 considered the minimum.

 

[narvlebenoit]

Re: prop pitch johnson 150 1999

I have a 18 foot startos282 with a 150 fast strike 1997 with a 21X14 and it truns 6000 rpms at wot.

 

[phoenixgold2100]

Re: prop pitch johnson 150 1999

I have a 18 foot startos282 with a 150 fast strike 1997 with a 21X14 and it truns 6000 rpms at wot.

What is your top speed with that 21 pitch?

From what I have read 110 pounds of compression is high for a v6 looper. Something to do with ports in the sleeve.

Would a smaller diameter prop turn out some more rpms?

I could get a 4 blade 22 13.25 prop for 150 right now. But I am not sure this will give me more rpm

 

[dan02gt]

Re: prop pitch johnson 150 1999

Typical performance of a 17-18 ft bass boat powered by a stock 150 is 60-62 mph.

The guy that claims 70 mph is not telling the whole story. Like he's hiding a 200-225 power head under that 150 cowling on a stripped down Bullet.

+1

I've been a member at Bass Boat Central for a while now and excluding the ultra high performance hulls from companies like Allison, Stroker, and Bullet, 60-62MPH is about what your going to get our of a properly setup 17-18'/150 HP combo. My brother had the Javelin version of your boat years ago with a 150 Johnson and it would run low 60's but no more.

I do think you could get a little more out of it with the proper prop, but I don't think 70 is even remotely possible without more power or a much lighter hull.

The Raker or a Tempest Plus in 22P would probably be the ticket.

 

[steelespike]

Re: prop pitch johnson 150 1999

If you check some 4 blade props in 22" you will note the diameter will be less than that of a typical 3 blade 22" prop.
The reason is the additional blade adds resistance.Usually if going to a 4 blade you would subtract an inch of pitch to maintain rpm.
The 4 blade is usually designed to perform best in low to mid range speeds.Improving hole shot,maintaining reduced cruising speeds easier,running smoother,and responding better around the dock.
While not carved in stone it is a safe bet you will lose top speed with the 4 blade.

 

[phoenixgold2100]

Re: prop pitch johnson 150 1999

My prop is 14.5 x 24 raker. this 4 blade is 13.25 x 22. I am hoping to get a few more rpms and maybe a bit more speed with this prop but Do you think I should get a 3 blade 22?

 

[dan02gt]

Re: prop pitch johnson 150 1999

My prop is 14.5 x 24 raker. this 4 blade is 13.25 x 22. I am hoping to get a few more rpms and maybe a bit more speed with this prop but Do you think I should get a 3 blade 22?

If you want more top speed then yes, but make sure it's the right 3 blade (Raker or Tempest Plus). I don't think you would be happy with the 4 blade your talking about. It's such a small diameter your probably going to have to lower your motor some to keep it from slipping (assuming you have a jack plate) which is going to cost you speed. If you want to try a 4 blade I would recommend the Mercury Trophy Plus.

 

[jestor68]

Re: prop pitch johnson 150 1999

I trust that by "Raker", you're referring to the current Raker II, which is improved over the original Raker prop.

The Raker II will allow you run higher motor heights AND deliver more bow lift compared to the old Raker.

 

[dan02gt]

Re: prop pitch johnson 150 1999

I trust that by "Raker", you're referring to the current Raker II, which is improved over the original Raker prop.

The Raker II will allow you run higher motor heights AND deliver more bow lift compared to the old Raker.

I was referring to the original but the Raker II would work well also. Although most of the guys on Bass Boat Central seem to prefer the original to the Raker II. The Raker II has more rake and does provide more lift, and has the interchangeable hub. The problem with it the steel that is used is softer than the original so it just doesn't hold up as well.

 

[steelespike]

Re: prop pitch johnson 150 1999

There you go.

 

[jestor68]

Re: prop pitch johnson 150 1999

The problem with it the steel that is used is softer than the original so it just doesn't hold up as well.

Have anything to back up that statement; other than you heard it on the internet? :faint2:

The guys at Evinrude might have some input on that.