TJY99

High altitude engine choice on new 264 Sunesta

7 posts in this topic

Just ordered a 2013 264 Sunesta and we are very excited for it to arrive. However, after spending some time on the forum, I'm second guessing my engine choice. I ordered VP 320, based on our salespersons recommendation. He stated that we would be very happy with the 320 hp engine. I also added trim tabs to assist in plaining. My concern is that we will always run the boat at about 4500' elevation (Canyon Ferry Lake, Helena MT), usually with a boat load of teens wanting to raft, ski, kneeboard, and wakeboard. The salesperson spoke to the Chaparral rep and confirmed that this setup would be just fine and not really worth the $ upgrade to the 380 hp.

Here's my experience with our past boat. A 2004 Four Winns Horizon 230 with VP Gxi 5.7 320 hp single prop. Lots of prop issues, never really solved, but ended up with an adequate prop that had good hole shot, but only a top speed of about 35 mph. I know that having the dual props and trim tabs on the new 264 will help all the way around, but the 230 weighs about a 1000 pounds less that the 264.

With this being a $ boat, am I making the right choice with the 320 hp vs. 380 hp?

Thanks for your thoughts!

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Highly recommend going with the most hp option. The 264 Sunesta not only weighs an extra 1000 lbs. but also has a deeper transom deadrise of 22.5 degrees, which requires power. You won't regret the extra power IMO.

On a side note, I don't know who many people you regularily boated with on your 230 Four Winns, but if you had the 320 GXi version, it should have had better performance at the top end. Mayhap you had it configured for water sports, and/or a load of people on board?

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Ordered with the high altitude option, your new boat should be just fine with the 320 motor.

I have a 05 204ssi with a 270hp GXI drive. I have had trouble turning more than 4600 rpm at high altitude, no matter what prop I have tried.

There is a Volvo service bulletin that gives recommendations for gear ratio for high altitude.

My boat also was from california and did not have the correct gear ratio. That may have been the problem with your old boat.

http://www.marinemec...ituderatios.pdf

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At a known high altitude you WILL NOT develope the assumed sealevel rated horsepower .

Thinner air equals less Oxygen. Less Oxygen equals less horsepower Add in a very hot dry day & you will wish for the biggest engine.

Too much horsepower on a cool damp day ? Use less throttle..

Take you best shot at enough H P when you order. Change the order today. Should not be a problem.

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I just purchased a 2012 Sunesta 264 and opted for the 400hp engine. Further, I worked with the dealer on a prop change, and a lower unit gear change based on Volvo's suggestion. As I recall; Volvo suggested the gear change at altitudes over 3000' (or maybe it was 3500')

We will run our boat at 8000' almost all the time. I have not had it in the water at altitude yet; but I was very please with the performance at ~1000' on Lake Mead.

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On 25/04/2013 at 6:58 PM, cyclops2 said:

At a known high altitude you WILL NOT develope the assumed sealevel rated horsepower .

Thinner air equals less Oxygen. Less Oxygen equals less horsepower Add in a very hot dry day & you will wish for the biggest engine.

Too much horsepower on a cool damp day ? Use less throttle..

Take you best shot at enough H P when you order. Change the order today. Should not be a problem.

yup, all true, the water is thinner too, your boat sits slightly deeper since the SW boat does not change but the SW from the water does, If you add salt to water, {saltwater versus fresh water}  the water is heavier, thus your boat floats higher and has to push less water out of the way to move, besides that props have a better grip in heavier water too.

For everyone thinking i'm joking, click the link http://www.infoplease.com/cig/science-fair-projects/objects-float-better-salt-water-fresh-water.html

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This is a 3 year old topic already answered about altitude, oxygen content, and the impact on engine performance.

Have no idea how you got from air and oxygen content to water and salt content, but since you brought up the Archimedes' Principle, you could calculate exactly how much higher will the same 22 foot boat of 3000 lbs sit in the salt water versus fresh water.

Let me know ... or post in the topic linked below ... he needs a new fresh water tuned prop ... :D

 

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