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New R5/380 only making 50-51mph
Posted: Fri Aug 16, 2019 3:34 pm
by greenhut
FH6 props. 50-51 according to Garmin GPS. Hitting close to 6k RPMs but will need to check. Was expecting 53-54ish according to Cobalt's docs (see below). Clearly an error in the doc as there are two lines for the R5/380 with identical equipment and different results. Perhaps is FH5/FH6. Religiously have followed Volvo break in guidelines which do allow for small amounts of WOT after 2hrs. At about 8 hours now.
Less than half a tank of gas. Boat isn't empty - misc gear/floats/anchor. 2 passengers. Smooth conditions, little wind, trimmed aggressively for speed.
Another 3mph is really not a big deal - until the redneck in me (or my wife) surfaces and we want to leave someone in our fumes
What are you guys seeing?
image1.jpeg
Re: New R5/380 only making 50-51mph
Posted: Fri Aug 16, 2019 4:09 pm
by tgrace98
What were the weather conditions like? Altitude?
Re: New R5/380 only making 50-51mph
Posted: Fri Aug 16, 2019 6:09 pm
by dmnouri
When the water is smooth I can get my 350hp to hit 52-53 with the trim up at level 4. Has 28 hours on it.
Re: New R5/380 only making 50-51mph
Posted: Fri Aug 16, 2019 7:36 pm
by BobRae99
greenhut wrote: Fri Aug 16, 2019 3:34 pm
FH6 props. 50-51 according to Garmin GPS. Hitting close to 6k RPMs but will need to check. Was expecting 53-54ish according to Cobalt's docs (see below). Clearly an error in the doc as there are two lines for the R5/380 with identical equipment and different results. Perhaps is FH5/FH6. Religiously have followed Volvo break in guidelines which do allow for small amounts of WOT after 2hrs. At about 8 hours now.
Less than half a tank of gas. Boat isn't empty - misc gear/floats/anchor. 2 passengers. Smooth conditions, little wind, trimmed aggressively for speed.
Another 3mph is really not a big deal - until the redneck in me (or my wife) surfaces and we want to leave someone in our fumes
What are you guys seeing?
image1.jpeg
How many hours do you have on your boat?
Re: New R5/380 only making 50-51mph
Posted: Fri Aug 16, 2019 8:32 pm
by Big Block Power
Ok sorry side track Matt you can get a R5 with a 520 in it. What.
Guys we need to get some of these on the water.
You need a good little chop and cooler Temps and the engine and drive will break in more she will gain a few mphs
Re: New R5/380 only making 50-51mph
Posted: Fri Aug 16, 2019 10:06 pm
by cmattj
Big Block Power wrote: Fri Aug 16, 2019 8:32 pm
Ok sorry side track Matt you can get a R5 with a 520 in it. What.
Guys we need to get some of these on the water.
You need a good little chop and cooler Temps and the engine and drive will break in more she will gain a few mphs
Agree bb obviously as everything is relative to weight x horsepower x Drag.
One thing to add that Tgrace touched on is weather vs Horpower.
Lake Lanier is already at a 1,000 feet above sea level. Add the humidity and low barometer, and effectively your boating 3500-4000 actual density altitude.
So the 380 corrected hp rating will be down 50hp ish.
Good news is the it could be worse..
Re: New R5/380 only making 50-51mph
Posted: Sat Aug 17, 2019 6:41 am
by tgrace98
Yep what Matt said! Lol
I can tell you in the spring my R7 would hit about 52-53. On a 90+ degree day I’m lucky to see 50.
Re: New R5/380 only making 50-51mph
Posted: Sat Aug 17, 2019 7:41 am
by Traveller14
7D5B7ECE-566C-447A-B138-9A66FFBD8018.jpeg
Ok I just did this Thursday. Calm water and about 75 degrees with about 750 miles on the 430hp. I was playing with the trim trying to find optimum. It bounced between 56 and 57.5 this day. I had the Bimini folded up which helps. The only thing left to do was find some chop which seems to add a bit more as I have been in the 57-58 range before. The rpm won’t go past this number so not sure how you guys red line it.
The 2 below show what the trim did for me will all else the same. WOT is fun at 34 degrees when you hit a small wake. The big boat feels like it’s floating for a few moments
C643E158-40CA-43F4-88D7-B35472B9B945.jpeg
0E44F20E-7568-4293-B0F2-E5042FD04057.jpeg
Re: New R5/380 only making 50-51mph
Posted: Sat Aug 17, 2019 8:32 am
by BobRae99
The OP doesn’t say how many hours he has on his less than 2 week old boat, but I’m thinking maximum performance will come after some hours are accumulated.
Cobalt told me that the numbers on their published prop charts are taken from one run with light fuel and one person on board and are used as a guide to help customers select power, but they don’t guarantee the published results because it is just one run and there are many variables.
Re: New R5/380 only making 50-51mph
Posted: Sat Aug 17, 2019 11:35 am
by dmnouri
This his what i got today. 80 outside.
Re: New R5/380 only making 50-51mph
Posted: Sat Aug 17, 2019 12:14 pm
by greenhut
Thanks for all the responses - I had mentioned that I was at about 8 hours - perhaps as it breaks in I'll see more performance. Very hot in the ATL area (lanier) Well over 90 degrees when I tested - never realized this impacted output!
Re: New R5/380 only making 50-51mph
Posted: Sat Aug 17, 2019 12:30 pm
by Big Block Power
Yea I gain a few in the fall plus I take a picture while going with the current
Re: New R5/380 only making 50-51mph
Posted: Sat Aug 17, 2019 6:53 pm
by BobRae99
greenhut wrote: Sat Aug 17, 2019 12:14 pm
Thanks for all the responses - I had mentioned that I was at about 8 hours - perhaps as it breaks in I'll see more performance. Very hot in the ATL area (lanier) Well over 90 degrees when I tested - never realized this impacted output!
I opened mine up at15 hours and hit 52mph. The charts say it will go 54, but I’ll never run at top speed for long anyway. We seem to be happy tooling along at 28 - 35 mph. When I want to really fly, I just hop on our Sea Doo, I’d goes about 70.
Re: New R5/380 only making 50-51mph
Posted: Mon Aug 19, 2019 3:06 pm
by JavaEboy
I'm not sure if you will see the same difference with the Cobalts that I had on my older non-Cobalt bowrider.
For me, I was able to get the fastest top-end on my boat when I had the bow cover and old-style convertible top and side windows deployed. My guess is that it helped with airflow and actually pushed the boat into the water, allowing me to trim my boat differently.
I'm not sure where the performance charts can be found, but it would be interesting to see the performance charts from the years that Cobalt offered both bowrider and cuddy versions of similarly sized Cobalts.
I know that really doesn't help much, but thought I would throw in my 2 cents.
Re: New R5/380 only making 50-51mph
Posted: Sat Aug 31, 2019 10:06 pm
by Jeeper
I would be happy to get 50 mph out of my R5 Surf with a 380. The best I have ever done is 46 mph at Lake Powell that is about 3600 feet, maybe it would do better at a lower altitude.
