jid

Should I change prop on sunesta 232

38 posts in this topic

After a long and painful process, the new (remanufactured) 5.7 mercruiser is not only in, but the boat it running really well!  

currenty have 24p props on the bravo 3 outdrive.  I am hitting 4600rpm at 44mph with just me (no kids, no gear) and trimmed up properly on glassy water.  

So the question is:   Will I lose or gain top speed if I switch to 22s?    The launch is pretty strong as-is with the 24’s.   22’s will bring me close to the top of the RPM band.   Towing kids 22’s may be just right.  Any thoughts on this?  Has anyone moved from 24’s to 22’s like this before?

Joseph

Share this post


Link to post
Share on other sites

I prefer to prop for the high end of the recommended range. Going to 22's should put you up close to 5000 RPM. Great for pulling tubbers, but may not be great for cruising. Check to see what the correct WOT range is for your reman 5.7. It may only be 4800RPM max, in which case I would stick with the 24's.

I am running 24's. Boat came with 26's, also tried 22's.  The 24's were preferred for my set-up. 

brick

Share this post


Link to post
Share on other sites
4 minutes ago, brick said:

I prefer to prop for the high end of the recommended range. Going to 22's should put you up close to 5000 RPM. Great for pulling tubbers, but may not be great for cruising. Check to see what the correct WOT range is for your reman 5.7. It may only be 4800RPM max, in which case I would stick with the 24's.

I am running 24's. Boat came with 26's, also tried 22's.  The 24's were preferred for my set-up. 

brick

Thanks for the feedback!  

I did speak w the engine manufacturer and they said that 5k rpm would be fine and that they would still honor the warranty on the motor if I ran it there.  Something about the fuel injection tables not going much higher than that on the EFI motor but that the internals of the motor were plenty capable.

since you went through the same challenge as me, what didn’t you like about the 22s?  Was it fuel consumption? Loss of top end?  Just felt like it was ‘over-spinning’?   I still have my 26’s and a friend is going to loan me 22’s to try.  I already feel like the 24’s may be the ticket...  they run strong and hard right now.  

I’ll have 4 mid-sized adults out today so I can give it a good run with the 24s to see how they do. I’m guessing quite well.

no idea how 26’s did with this motor.  Was top speed higher with 26’s or just better fuel efficiency?   I haven’t run this motor with the 26’s so I’m very curious as well.

Joseph

Share this post


Link to post
Share on other sites

With the original 26's, my boat ran well, but topped out at 4400RPM, which is below the 4600 to 5000 WOT RPM range for my boat. I liked the 22's for water sports, but topped out at 5200.  At cruising speed it felt a little high. So the 24's are a compromise that seems to work the best all-around. I would probably like 23's, or 24's - but with a 2.2 drive ratio in place of my current 2.0 ratio.

brick

Share this post


Link to post
Share on other sites

I originally thought my 2005 Merc 350MAG/MPI had a 4800 to 5200 WOT rating, but according to Merc and my serial number, it is 4600 to 5000.

brick

Share this post


Link to post
Share on other sites

Great info! Do you recall by any chance what your top speed was with the 22’s or 26’s?   I have a feeling 24’s are gonna e the ticket but just want to validate my own sanity.  And save two extra prop changes if I can. :)

Share this post


Link to post
Share on other sites

The speed did not change by more than a mph or two. The higher RPM compensates for the lower pitch props, so pretty equal top speed (but at different RPM's). And the engine simply runs out of power with the higher pitch prop. 

The key is to be in the correct range with your normal load, and you might be a little low with your 24's. 

brick

Share this post


Link to post
Share on other sites
2 hours ago, brick said:

I originally thought my 2005 Merc 350MAG/MPI had a 4800 to 5200 WOT rating

That's what my manual reads, is that that where you got your original figures? 

Share this post


Link to post
Share on other sites

My 5.7 says 4400-4800 on the cover.   Loaded with 4 people it for up on plane almost as fast as it did with just me.  And still topped out at 4600rpm.  44mph via GPS.  Not too shabby for the end of Nov! ;)

 

 

Share this post


Link to post
Share on other sites

I guess WOT is the only thing that matters ?   Having 8 to 10 people & gear with a sudden dark storm line of clouds is unimportant ?

Going to WOT & getting on a full plane before the 3' waves  arrive at your dock is not important ?

That is what I prop for. When your guests look at a endless line of clouds coming at them & then ask are we going to get hit ? The prop with less pitch is HIGHLY desired.

Changing to the less pitched props is always correct.  The driver of your boat is supposed to be able throttle back to MAXIMUM rpms with a 2 or 4 some in the boat.

Good grief.     Charlie Brown. Take the wheel.  :captain:

If you do decide to really reduce the pitch to a VERY small number ?  To allow getting on plane with 10 to 15 people ?  Watch your gasoline drop rapidly FROM A FULL TANK LEVEL. Range is dropped a lot on some hull shapes.   My cruising area range & distance to get to my dock is 1/2 hour at WOT with a maximum # of people & goodies on board. I did a practice run LOADED to see my fuel consumption into the wind. Annoyingly very fast.

Too far from your dock ?  Head for any dock with a space ON THE DOWN WIND SIDE OF IT.  TIE UP TO IT.  Until safe enough to leave.

Really get caught in a no hope of making a down wind side of a sturdy dock ?    Pull up to a BIG cruiser tied to a dock. Let him break down the wind & waves for you.  It beats TRYING  to do a anchoring on unknown bottoms. I have now refused to try a anchoring in any bottom.   Run around the dead wind side of a WIND BRAKEING  island. Watch your depth gauge & charts if you are forced to move around the island...................If the wind direction FORCES you to move to a exposed area ? 

Oh well.  There is only so much you can do in desolate open island areas.  Try to pick a island where the low land side has a sandy beach to run the boat up onto the beach & save your people from bobbing up & down on a rock pile.

Laying  in a hand holding group for 2 hours. Is far better than a boat being pounded on wave crashing rocks or a vertical rock faced cliff.

Yes I have been caught in the above as a passenger & captain................. You need too be good. .............And lucky sometimes.

 

I now do not leave without all my super bad weather docks & islands preplanned on the cruise..................Need less luck.

Share this post


Link to post
Share on other sites

The 350 is not too thirsty below WOT. My fuel burn since new is 6.6gph. That is cruising at 3000 RPM and pulling the kids on a wakeboard at 2800 RPM.

At WOT, a 350 burns around 24 gph. 

As the OP is smack in the middle of the recommended RPM range with 24's, It sounds like his 24's are a good choice. 

brick

Share this post


Link to post
Share on other sites
17 hours ago, jid said:

My 5.7 says 4400-4800 on the cover.   Loaded with 4 people it for up on plane almost as fast as it did with just me.  And still topped out at 4600rpm.  44mph via GPS.  Not too shabby for the end of Nov! ;)

 

 

Those are solid numbers. What happened to the original engine?

i also don't see a huge difference in speed or RPM with a few extra souls on board. 

brick

Share this post


Link to post
Share on other sites

Original engine was misrepresented when I bought the boat.  15 min lake test is was fine.  It overheated after I bought it next time out.  Turns out one of the heads was cracked and repaired.  Poorly.  I had all service records from the previous owner but the engine work was conveniently left out of the pile.

anyway, it is running very well now.   Topping out at 44mph with those 24’s.  I may try 22’s just to see but these 24’s feel really good!

Share this post


Link to post
Share on other sites

If it came with 26's then the 24's should be good. You won't get maybe a mile or 2 mph at best by switching props. A decent increase in hp is the only thing that's going to make a speed difference. That hull just wasn't meant for it.

Share this post


Link to post
Share on other sites

I’d take 1-2 mph if I can get it.  Huge difference on this boat between 44 (which is what it hits now) and my previous cuddy cabin which would only hit 42.  I know it doesn’t sound like much but it is for someone who likes to make runs up and down the short lake out here.

Share this post


Link to post
Share on other sites

Sorry on the original engine. I think you will be pleased with the new one...

brick

Share this post


Link to post
Share on other sites

So far so good.  New motor didn’t have timing marks on the crank so I estimated.   And it is running well.  But I’ll re-time it with some timing tape and then it will be spot on!

Share this post


Link to post
Share on other sites

I wonder if the original engine damage was caused by being over-propped with 26's.  "Lugging" an engine will cause early failures. 

brick

Share this post


Link to post
Share on other sites
On 11/24/2017 at 8:49 PM, jid said:

So far so good.  New motor didn’t have timing marks on the crank so I estimated.   And it is running well.  But I’ll re-time it with some timing tape and then it will be spot on!

If your engine RPM range is 4400-4800, then I'm thinking the engine is either a MerCruiser 5.7L carbureted model, or maybe 5.7L EFI. If the boat was mine, I would do the following depending on power train and options boat currently has on it.

- install extended swim platform (if not already equipped with one)

- install SeaDek pad for greater grip and comfort (link below fits factory OEM extended swim platform)

http://www.seadek.com/p-495-chaparral-232-234-sunesta.aspx

NOTE: the 2 options listed above IMHO are by far the best bang for the buck for water sports and general all around daily use.

* if engine is carb'd, install 4 bbl Weber or Edelbrock carb (intake, fuel line, brackets, etc. from say 1996 MerCruiser 5.7 LX) vs. spending roughly similar money on different props

* if engine is EFI, there is a guy in California who can do a recal on MEFI 1 and 2 ECM'a for extra power.

- place the drive in the Bravo 1 position, and adjust the trim senders for faster hole shot with less bow rise 

Lastly, for owners who have MerCruiser 350 Mag MPI engines, Merc changed their top RPM spec numbers sometime around 2005 to 4800-5200. If memory serves Merc changed the cam and ECM calibration for the extra 200 RPM.

Share this post


Link to post
Share on other sites

I’ve done -most- of those things.  This one is an EFI.  Any more info on who the guy is there that can get more power out of the ECM?   That sounds promising for sure!

LOVE SeaDek!!!  My favorite material ever!!

Share this post


Link to post
Share on other sites
5 hours ago, Shepherd1 said:

 Lastly, for owners who have MerCruiser 350 Mag MPI engines, Merc changed their top RPM spec numbers sometime around 2005 to 4800-5200. If memory serves Merc changed the cam and ECM calibration for the extra 200 RPM.

Yup. That's why I originally thought my 350MAG/MPI WOT range was 4800 to 5200. But according to Merc (recently) per my serial number, is 4600 to 5000.

brick

Share this post


Link to post
Share on other sites
9 hours ago, jid said:

I’ve done -most- of those things.  This one is an EFI.  Any more info on who the guy is there that can get more power out of the ECM?   That sounds promising for sure!

LOVE SeaDek!!!  My favorite material ever!!

Here's two options. Still trying to recall the guy from California that I had heard of.  As far as I can make out, Bob from mefiburn has some serious internet cred.

http://www.mefiburn.com/mefituning.asp

http://mefituning.com/mefi-calibration-and-hi-performance-engine-services

Share this post


Link to post
Share on other sites

It takes a lot of additional horsepower to increase boat top speed. An online boat speed estimator shows you would need 330 HP to achieve 50mph, extrapolated from 260 HP and 44 mph top speed. That's s big increase in HP.  

brick

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now