Correct prop?

[Jclarke81]

Hello, longtime lurker reading and learning a lot. I am a little perplexed on my current prop situation. I currently have a 98 Rinker 233 BR with a 5.7l 2 bbl carb. I had a 4 blade 19 pitch SS power tech prop on it that would put WOT 3400 rpms 34 mph. All the calculators and local prop shop said to go down to a 15 pitch. Got a Turning Point 4 blade 15 pitch AL prop for cheap to test it out. Went out this past weekend and get WOT 4400 36 mph. We do mostly water sports and cruising. Have young kids and nephews that like to tube and wakeboard etc. Everything seems fine I just thought I'd get more top speed than that. Engine was tuned up last year and everything seems to be working fine.

Thanks for any help/ tips.

 

[alldodge]

No more speed, to do that you need more HP

 

[Jclarke81]

Thanks for the reply.(Its a rinker 232 sorry for the typo) I was figuring that might be the case. All the calculators said I should get close to 45 mph. And other similar set up boats I've been on are getting upper 40s lower 50s with the same engine/ outdrive. Just figured maybe I'm missing something.

 

[porscheguy]

You are missing something: a 4 barrel carb. Seriously.

Its borderline criminal that Rinker put such an anemic engine in that boat when a 454 was also available.

 

[alldodge]

There were many 232's sold with the 5.7 because it made the boat cheaper. They do ok with a B3 drive, but nothing like one with a 7.4 motor. Rinker is just like most other manufactures, they sell smaller motor packages for the same model

 

[NYBo]

Welcome to iBoats! :welcome:

Make sure your motor is putting out full power. Start with a tune-up (if not done recently) and a compression test. Is the throttle opening fully? Spark advance in the distributor working properly?

 

[Jclarke81]

Thanks for the reply. Just had a tune up towards the end of last season. At the time it appeared to open all the way at full throttle. I didn't check compression or timing. I don't own either tool but will see if I can get my hands on a timing light. I know you can rent the compression testing tools at any auto parts store.

 

[Jclarke81]

Talked to the shop that did the tuneup. Compression and timing were checked then and were in spec. It's looking more like this just might be the most I get out of the 5.7l.

 

[alldodge]

WOT 3400 rpms 34 mph 4-blade 19
WOT 4400 rpm 36 mph 4-blade 15

You need to get away from 4 blade props, while they provide more lift, they also need more power to turn. Need to get your RPM up around 4600 to 4800. Normally the boat with that motor would come with a B3 drive and 2.0 ratio. Not sure but the drive sounds to have a 1.5 ratio.

Suggest trying a 17-3 blade

My 232 does 60 mph with a 3-blade 21

 

[tonyjh63]

This does seem kinda strange...you'd think an additional 1000 rpm would produce more than 2 more mph. Seems like prop slip is going up considerably. Are these speeds measured via GPS?

 

[Jclarke81]

All have been measured by GPS as the Speedo tops out at 25 mph. It's increased 1000 rpms but prop changed from 19 ss to 15 al. What gets me is I'm still at the low end of the rpm range. Just a thought, I can get my hands on a 1.62 outdrive at a decent price. Would that make a difference?

 

[alldodge]

I can get my hands on a 1.62 outdrive at a decent price. Would that make a difference?

For the most part that will just change your prop from 15 to lets say a 17. I'm guessing what you have, and changing the ratio may not help, just depends how the boat responds

 

[porscheguy]

Check to see if your water shutters in your exhaust are intact. It’s free, and takes 10 minutes. If you’ve got a broken exhaust shutter it could be blocking your exhaust and reducing your power. And even if they were fine last year, that was last year. They work until they fail and fall apart. You certainly wouldn’t be the first person who found the self struggling for speed and discovered a broken shutter.

 

[Jclarke81]

To those wondering, it's an alpha gen 2 drive with 1.5 ratio. I'll check the shutters this weeked. I had a 19 pitch 3 blade on it laat year that did close to the same top speed as the 4. Went with the 4 blade again due to the kids wakeboarding etc. Alldodge, missed your earlier post. I can't imagine 60mph!