Dock Talk #1: w/Steve Locke - "Powering your project"

 So, you have a project Cobalt and starting to think, “hmm… what would really be the best power plant for this?”

A lot comes to mind as you start to weigh your options on horsepower vs weight, or Volvo Penta vs Mercruiser. There is A LOT to consider and I’m sure you don’t want to break the bank to get there.

The majority of the drivetrains are powered by Chevrolet engines, which are tried and true and can last a very long time. But what size? Big block? Small block? For the 19’ and under, a small block 5.7 with 260-300hp is the sweet spot. Not too heavy, but a healthy amount of horsepower to get you on plane and into the low 50’s for top speed.

A 5.0L will also fit the bill with a healthy 200-240hp, but it is the same block as a 5.7 and therefore the same weight. Move into the later EFI models and you might be able to squeeze a couple more ponies out of it.

So….. you want to go a little, faster? Some classic owners have the need for speed and been putting in some extra HP. There are some big block 7.4L classics out there, most commonly in 21BR and 21CC models. But a few repowered with big blocks in the 19BR and CD models. It will surely get you some extra mph on top end and launch you out of the hole getting on plane, the only problem is the added weight.

Want the extra power of a big block but the weight of a small block? Here’s where stroker motors come in. a 377 (6.2) or 383 (6.3) is an excellent option for the smaller boats that want to go faster. A lot of crate motors come right from the factory with up to 400hp and loads of torque. Now we’re talkin’!!

Now…. what do you want to put behind that American muscle V8? Volvo Penta vs Mercruiser. Both can be great power plants and very reliable. Of course they each have their own quirks but you really can’t go wrong with either.

Personally, I am a fan of the classic Alpha 1 Gen 1 look. A ton of Cobalt classics were powered with a Mercruiser 260hp with an alpha 1 behind it, and I understand why. It’s fairly simple to work on, parts are everywhere, and they don’t hurt your wallet. With regular routine maintenance an Alpha 1 can easily last over 1000 hours of use.

One of the nice things about Mercruiser is they never really changed that much over the years, and that includes the transom cutout in the back of the boat. A 1975 Cobalt that had a Merc 260 in it could be replaced today with a brand new Merc drivetrain, and you wouldn’t have to do any kind of fiberglass work.

Volvo Penta eventually started using the same exact cutout in 1994 when they bought out OMC and adopted their Cobra stern drive system. The Volvo Penta SX and DPS outdrives are pretty much bulletproof and can handle a ton of power. They are smooth shifting due to the cone clutch style shifting and very easy to work on. The only problem is they cost considerably more than a Mercruiser.

I don’t want to ignore the older style 280 and 290 style drives, but these are even more expensive due to the fact that parts are getting harder and harder to find.

I would much rather have a power train I can keep going for years to come and not worry about breaking an unobtainable part.

If you would like to discuss more about your project, please feel free to email us at [email protected]

We’d love to chat!

YourClassicCobalt.com


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