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Been really loving my 2001 Cobalt 226 with 5.7 280 HP this summer. Piled quite a few miles on it. A few times I have put the hammer down and am very pleased with the speed. Just wondering how these engines last at WOT? Mine is running around 5000 RPM when wound out. I have found lately that 3000 RPM seems to be a good cruising speed if not in a rush. What RPM do you find is your sweet spot? What RPM typically gives the best fuel economy? Are these motors and drive systems happy at WOT?

Tia.

WOT on a boat is far harder than WOT on a car. The pressure and effort on a boat engine only increases with WOT. Even on plane a boat has a tremendous amount of drag that only increases with speed. There is no multi gear transmission to keep the engine in its rpm sweet spot. Everyone knows running your car at WOT all the time will kill the engine pretty quick. Imagine if the transmission in your truck got stuck in 3rd gear and you could only drive in that one gear regardless if you were tooling around in the city or blasting WOT down the interstate. Additionally, I once heard the effort on a boat engine is like driving a car uphill. Water exacts a lot more drag on a boat than air or tires on a car. Most boats are also moving a lot more air out of the way than a car does. Combining water and air drag is a lot of resistance to overcome.... again all in one gear. You can begin to see how the stress on the engine is different. That is kind of what it is like for a boat engine.

Your marine 5.7, GM/Chevy engine is nothing more than an over built version of its automobile derivative. It does have a vastly different camshaft profile, more piston to cylinder clearance, and all of the bolt on accessories, distributor, carb/FI, intake manifold, alternator, starter, water pump, freeze plugs, ...., are marine versions.

For me, 3,000 rpm nets me 35mph when I have the Duoprop trimmed just right for the conditions, which is a good speed. I have a 2006 220S open bow running a much larger engine - Volvo Penta 8.1 liter (GM 496ci) running a Duoprop (which also helps with with prop efficiency).

Generally, marinized car engines are stronger built than their car cousins, that said, its still not a good Idea to go WOT for extended periods of time unless you like rebuilding/replacing the engine(s). Have fun, be safe, enjoy your great boat.

Stay he just said and you are operating right where you should be. Your rpm might be a few 100 too high but your guage could be off if your not hitting a rev limiter. I think on your engine cover it will tell you max rpm I think is 4800. But your ok just don't run it long there. We All just do short blast pod wot.

Big Block Power wrote: Sun Jul 23, 2017 6:08 am Stay he just said and you are operating right where you should be. Your rpm might be a few 100 too high but your guage could be off if your not hitting a rev limiter. I think on your engine cover it will tell you max rpm I think is 4800. But your ok just don't run it long there. We All just do short blast pod wot.

You're up early today BBP. Not as early as me though

I also usually run at 2500-3000 rpm. That's around 25-35 for my boat. When my lake gets crowded it gets rough and that's fast enough.

Some mornings when I'm up early, it's calm, and my wife is no onboard I'll air it out. I've seen 57, but that's too fast for me on a boat.

Just one other comment. My owners manual says the Bimini is rated to 35 mph. Discourages driving faster. Most of the time in the summer I have mine up.

Good info Dan,.and spot on. Thanks.
And Good Morning to the rest of you Cobalt Lake bums!

Dan's info gave me a new perspective on running at WOT. Makes total sense, even a dummy like me could understand.

I'm not a WOT runner. Boating for us is about backing down and enjoying the day. But there is no doubt that running the engine at its limit is much tougher on fuel and parts.
Newer engines, especially the brand new engine platforms like mine are built on a cast aluminum foundation. Lighter, faster, more efficient power to weigh ratio, and better on fuel because of the weight savings....and IMO, NOWHERE near as tough as the old cast iron blocks that can last generations.
Knowing that, I don't plan on daily abuse....

Great answers, thanks. Did not know the Bimini top was rated at 35 mph. We had very heavy winds yesterday and was thinking it looked quite stressed. Do any of you with more recent Cobalts have a fuel economy gauge? If yes, what speed or rpm does it usually max out at?

I do, and about 3500 delivers the best economy.

I was going to say I think almost in any boat like ours it's 3000-3500. I know I've pushed my binimi over 40+ many of times no issue. I think it creates down force

The way it's secured down, front, back, middle and six Velcro side connections, I think it could take interstate speeds. My side tubes turn like a turnbuckle that really takes all of the slack and flap out of the top. I've had the boat over 50 mph, and the top didn't look any different than at 20 mph.

One of the first things I noticed when trying my boat out was a "whining" sound in the engine. After buying the boat & reading the manual on my engine, the Maximum rpm range was 5400-5800, which seemed high to me. The other thing was variable valve timing, which I know nothing about. But I agree that boat engines get a lot of abuse & maybe the newer engines are addressing this issue.

The other point I wanted to mention was about Bimini tops. The boat I just traded had a nice Bimini that had 2 straps in front & 2 straps in back. It also had the 35 mile per hour warning. One of the items we had always admired about the Cobalts at the boat show was the solid Biminis with the sales guy doing chin ups to prove it's strength, adding that you'd never have to take it down running the boat. This is the Bimini Tuscany mentioned with the stainless steel turnbuckles.

These are nice but the $1,800+ price made me cringe. I wonder if some boats were ordered without the Cobalt Bimini & then the top was added by an owner at a later date. Sorry for the long post & don't expect any pictures of me doing chin ups.

Dub

Alaskabound wrote: Mon Jul 24, 2017 9:55 am One of the first things I noticed when trying my boat out was a "whining" sound in the engine. After buying the boat & reading the manual on my engine, the Maximum rpm range was 5400-5800, which seemed high to me. The other thing was variable valve timing, which I know nothing about. But I agree that boat engines get a lot of abuse & maybe the newer engines are addressing this issue.

The other point I wanted to mention was about Bimini tops. The boat I just traded had a nice Bimini that had 2 straps in front & 2 straps in back. It also had the 35 mile per hour warning. One of the items we had always admired about the Cobalts at the boat show was the solid Biminis with the sales guy doing chin ups to prove it's strength, adding that you'd never have to take it down running the boat. This is the Bimini Tuscany mentioned with the stainless steel turnbuckles.

These are nice but the $1,800+ price made me cringe. I wonder if some boats were ordered without the Cobalt Bimini & then the top was added by an owner at a later date. Sorry for the long post & don't expect any pictures of me doing chin ups.

Dub

I forgot to include the drag of the bimini in my comments about drag on a boat and elevated stress on a marine engine. That bimini generates a ton of aero drag.

Well Dub, if you aren't gonna do pull ups from your bimini, I'm not going to do one hand hand stand push ups on the bow. No need for us to show off.

Alaskabound wrote: Mon Jul 24, 2017 9:55 am

These are nice but the $1,800+ price made me cringe. I wonder if some boats were ordered without the Cobalt Bimini & then the top was added by an owner at a later date. Sorry for the long post & don't expect any pictures of me doing chin ups.

Dub

Nothing is cheap when it comes to Cobalt my friend, especially top quality pieces like their Bimini.. it is one tough, we'll build piece.
If you are ordering, and want Cobalt top shelf, IMO, suck it up and get it done right from the factory.
Also, those high MSRP prices and options... don't let that scare you off, they are highly negotiable.