Hello from ARGO 2004 Cobalt 360

[ARGO]

Hello crew! New member saying Hi! 2004 Cobalt 360, dual 496HO (212 hours when bought), Bravo III ratio 1.81 (not positive). Bow thruster (LOVE IT!) Lots of new electronics Raymarine Axiom Pro 12 RVX, Ray73, Quantum 2, Fusion 755 etc. Mercruiser VesselView Mobile.

[ARGO]

Launch after the bottom job!

[ARGO]

VesselView wide open throttle - about 48 mph, I think I am underpropped (Hill Marine 4X4 new props 20 pitch). Cobalt says boat came out of the factory with 24 pitch but previous owner had 22 installed (he snapped a blade, thus new props).

[jhnmdahl]

Welcome Argo! Nice boat - it would be fun to see some photos of the inside as well.

Sorry if you were in new-member limbo for a bit - we had a problem with verification emails going out that has hopefully been permanently resolved. We used to use Gmail, but they kept changing security for remote apps to use their mail service and breaking the verification process. New verification mails and reminders should come from Cobaltchat.com instead of Gmail.

[ARGO]

Thanks, I was patiently waiting for the "approval" to join the forum. The Best comes to those who wait ! Will do more pictures.

[jwill323]

If you had the 24 pitch from factory i think they say to go down a size for the 4x4 so 22p would probably be the right prop 20 may be a little light. what rpm did you hit at WOT w/ the 20p? I have the 496HO's and the 24P 3x3 merc props on the 1.81 bravo 3X drives.

[ARGO]

give or take 4950 on both motors according to vesselview

[ARGO]

47-48 mph, I thought it would be closer to 57 (according to the independent testing done in 2001 - 50 knots per hour, 57 mph) maybe it was a wishful thinking.

[ARGO]

Boat test info for 360

[jwill323]

according to Merc the 48MPH looks about right for the 20P props

[jwill323]

22p looks to get you around 53MPH if you keep the same RPM but not sure you would. If i was going to make the change i think i would look for the original 3x3 props 24P or reach out to Hill and see what they say. Not sure what diameter prop the 20p Hill props you have are but they probably hook up great since it looks like only 6% slip. Holy Smokes on here has the exact same boat and went with the Hill 4x4 22p props and seemed really happy.

viewtopic.php?p=106631#p106631

Might want to reach out to Hill, maybe there is something they could do.

[jwill323]

1 other thought, not sure if you had compression checked on engines? Everything running good engine wise? I would think with the 20p you would be higher on the RPM's but there are a lot of variables at play there with the 4 blade props, bottom paint how loaded up was the boat when you ran it WOT did you have 10 people, full fuel, etc?

[jwill323]

ok 1 last thing! The test numbers you have from boat test is a different configuration, it was a 2001 360 with 502 engines, 2/1 gear ratio and 26p props so really a different boat but i couldn't find anything comparable to your set up. I run mid 50's on mine at WOT with the same engines and drives you have but mine is a 323 so a little lighter and no bottom paint. I think low 50's would be right for the 360 configured the same as mine which the 22p would get you right there. At the end of the day chasing a few MPH at WOT may not be worth it but you may be able to get a better more efficient, faster cruise with a different prop set.

[ARGO]

thanks for the info! Bottom job - new, compression is very good - inline with 212 or so hours, full synthetic fluids: engines Triax 25W40, drives Triax SAE90, new plugs, wires, K&N filters, fuel filters etc. calm day, 1/2 fuel tanks, 2 people onboard. I've talk to Hill and they suggested like you swapping to 22 4X4. My mistake was that I assumed that boat came with 22 out of the factory - but per Cobalt Boats she came with 24. I have no idea why previous owner swapped to 22??? I'll try to swap them with Hill. I wonder what will happen to cruise speed with 22? With 20 I am at 3000-3300 at 32-33 mph.

[jwill323]

I cruise a little faster then RPM with my set up 33-35mph at 3000-3200 i don't have the smart craft RPM data so just based on the analog rpm gauges but do have the GPS for the speed. That's with the 3x3 merc 24p the move down from 24p to 22p would be the right thing to do when going to the 4 blade props. The extra blade is a gain in efficiency (less slip) which lowers the rpm, by going to the lower pitch you pick back up the lost rpm's to keep the engines in the correct rpm range and not lug the engine. All this prop stuff is more art then science and i am no expert just read a lot of crap online while its too cold to boat here! Good luck, all things considered the current setup dosent sound bad, you have really low slip, a decent top end and it sounds like the boat is in great shape and cruises well, really just minor tweaks which is just the last little bit of performance. If you plan on crusing with a crowd on the boat you may just want to leave it as is, the more weight you pile on the more you may like the 20P props!