Correct prop size

[JBlaze]

First time boat owner. We purchased a 2001 Islander 270 in July that had an issue with one of the Yamaha 200 HP four stroke motors. We re-powered with Yamaha 150 HP four strokes but used the props( 15 1/4 x 17-M )from the old motors. We were only able to get the RPMs to 4900. I have just sold the old motors with the old props. My question is what size prop will get me to the recommended 6000 RPMs?
Thanks in advance for any help!
John

 

[Hookup1]

I switched to 4-blade props from PropGods.com. 268 Islander with F150's. Best decision I ever made.

 

[Ekea]

to get rpm with those engines will take a pretty small prop and i assume performance will unfortunately not be great. that is a lot of boat for 300 hp. call prop gods to try to get the most you can out of that set up.

 

[JBlaze]

I switched to 4-blade props from PropGods.com. 268 Islander with F150's. Best decision I ever made.

Thanks for the help.

 

[JBlaze]

to get rpm with those engines will take a pretty small prop and i assume performance will unfortunately not be great. that is a lot of boat for 300 hp. call prop gods to try to get the most you can out of that set up.

Thanks!

 

[Sardinia306Canyon]

As above,
not a lot of power for your boat, but Propgods will help you to find and maybe have worked the right ones.
Chris

 

[JBlaze]

As above,
not a lot of power for your boat, but Propgods will help you to find and maybe have worked the right ones.
Chris

Thanks! I just emailed them.

 

[Ekea]

let us know what they tell you and what you end up with performance wise

 

[Hookup1]

Thanks! I just emailed them.

Call them but have your performance numbers and prop sizes. Ken will compute slippage and make a recommendation.

My results are posted on GG search hookup1 propgods.com

 

[seasick]

What speed did you get when you topped out revs? Speed number should come from GPS plotter. not the Yamaha speedo gauge

Depending on the engine model and year, the lower unit gear rations might be different. The f200 has a 2.0 ratio but the F150 could be 2.0 or 1.86 depending on model year. I think the newer models 2014 or later have 1.86 ratios

So for a F150 with the 1.86 LU, at 4900 revs and 10% slip, you should be making about 38 mph.

 

[JBlaze]

What speed did you get when you topped out revs? Speed number should come from GPS plotter. not the Yamaha speedo gauge

Depending on the engine model and year, the lower unit gear rations might be different. The f200 has a 2.0 ratio but the F150 could be 2.0 or 1.86 depending on model year. I think the newer models 2014 or later have 1.86 ratios

So for a F150 with the 1.86 LU, at 4900 revs and 10% slip, you should be making about 38 mph.

Top speed was 35 from the Yamaha gauge, I didn't look at the gps. Rpm's were 4900. The motors are new 2022 put on the beginning of August.

 

[seasick]

The Yamaha gauge if the pitot tube type are inherently inaccurate. If you have the CL7 display and it is networked to your plotter, the speed is probably accurate.
Since your motors are 2022s, the LU gear ratio is1.86 whereas the ratio for the f200 was 2.0. I would not assume that the props would be the same specs for the different models.
In any case, your speed is close to my calculated speed. The slip is within range.
See what the prop gods have to say.

By the way, did you try trimming the motors to see if the WOT revs improved?
And I have to ask; Is the hull clean?

 

[JBlaze]

The Yamaha gauge if the pitot tube type are inherently inaccurate. If you have the CL7 display and it is networked to your plotter, the speed is probably accurate.
Since your motors are 2022s, the LU gear ratio is1.86 whereas the ratio for the f200 was 2.0. I would not assume that the props would be the same specs for the different models.
In any case, your speed is close to my calculated speed. The slip is within range.
See what the prop gods have to say.

By the way, did you try trimming the motors to see if the WOT revs improved?
And I have to ask; Is the hull clean?

Yamaha gauge is not networked to the plotter. I just upgraded the Garmin Plotter in September when we put bottom paint on. Yes, the hull is clean. We did try trimming the motors but WOT would not go over 4900. I'll keep you posted on the new numbers after I install the props.

 

[Sardinia306Canyon]

My Yamaha 250 is about 0.5-1 knot off, but that depends on each motor and hull.
You can easily connect the GPS with the gauge thru NMEA183 connecting two cables.

Chris

 

[BigD808]

Props and trim tabs make a huge difference on how the Grady rides IMO (at least the 232 gulfstream). I recently switched to Powertech 4 blades, and couldn’t be happier. I loss a little top end, but overall ride is smooth as silk now. 232 gulfstream twin 150 yamaha I gotta check size and pitch tomorrow.

 

[JBlaze]

Thanks everyone for your input. I ended up going with the Sola's 4 blade 14.5" x 15". I did not go through the whole progression and log the numbers yet but now at WOT we are at 5800 rpms and topped out at 38 mph. A great improvement. As a new boat owner I still have some work to do on learning when and how to trim properly which I'm looking forward to. Thanks again for your help. John

 

[Peter A]

If you need a spare prop I have a Solas Rubex HR4 14.5x15. Different boat so different story but when I got my 208 with F200 I replaced the HR4 with a 14x14 Powertech SCE4 from Ken/Prop Gods. I am happy with the outcome. The solas is in perfect condition, no nicks or dings and has low hours on the hub (between 20-100 hours max).

 

[BigD808]

Thanks everyone for your input. I ended up going with the Sola's 4 blade 14.5" x 15". I did not go through the whole progression and log the numbers yet but now at WOT we are at 5800 rpms and topped out at 38 mph. A great improvement. As a new boat owner I still have some work to do on learning when and how to trim properly which I'm looking forward to. Thanks again for your help. John

These are around the same numbers I’m getting on my 232 running powertech 15.25x15 @ wot

 

[Ekea]

glad it worked out and you are happy. did you get the props from prop gods?

 

[JBlaze]

glad it worked out and you are happy. did you get the props from prop gods?

No, I ended up getting then from the local marine shop that did the repower since they had them in stock and I needed to get them on asap since I sold the old props with the old motors.