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Log Entry

You're going to blow yourselves up!

We bought a powerboat driven by 30-year-old twin inboard GM 454 big block 350 horsepower Marine Power gas engines. Sitting atop the intake manifolds are thirsty Holley four-barrel carburetors. When the secondaries on those Holley's kick in at higher RPMs, it's like the proverbial "fire hose" spraying the gas into them.



When we tell our friends about it, they ask if we are worried about blowing up because the engines are gas. It seems the world has gravitated from gas inboards to diesel inboards. Inboard gas seems to be sort of a thing of the past for today's boat builders and buyers. But not for Holly and me.


As usual, I digress. My two daughters will attest to my love of hanging around boatyards and boatbuilders. I dragged them to many yards and builders when they had no choice otherwise. The picture here is of me chatting with Jarvis in 2013 at his shop.


Jarvis Newman

One of my favorite builders was the late Jarvis Newman. Whenever I went to Southwest Harbor, I'd visit Jarvis at his immaculate shop on the way into town. I developed a great respect for him and his opinions (he had strong ones) about boats and boating. Below, I'll get to the relevant points relating to this post.


In her seminal work, Maine Lobsterboats, Builders and Lobsterman Speak of Their Craft, Virginia Thorndike included a chapter about Jarvis. In it, she wrote the following about Jarvis's engine choices. "Interestingly, Jarvis doesn't like diesels". Jarvis said to Virginia when interviewed, "People just want to hear the throatiness," he scoffs. "It's not worth the hassle, and the noise, and the cost!"

I agree with Jarvis. And, yes, diesel engines can be noisy and need to be well insulated, or the sound onboard when running can be loud. However, our gas engines aren't exactly quiet. But the majority of the noise is behind us – emitted out of the four three-inch exhaust ports at the transom. Forward at the helm is not so bad, but when we start up at the marina, dogs run (including our dog, Becket), and children start to cry. Some of the adults – especially the sailboaters – shake their heads. This part is particularly hilarious given that Holly and I still sail and race and love windy days with a wistful longing to own a sailboat again... Breezy days are not ideal for powerboating but our gal is more than capable of a few windy waves. Again, back to the story.

At idle, the engine sound is what the President of Ray Hunt Design, Winn Willard, refers to as the exhaust having just the right "burble." At speed, the burble becomes more of a roar.

When I went to Westbrook, CT, to inspect the boat for the first time, I shot a short video with sound to let Holly know that the boat is not exactly quiet and what she'd be in for. When Holly played it, she loved the sound. Little did I know she was thrilled the sound was everything she'd hoped for.



So, we got past the noise issue (except for Becket, who doesn't even like raised voices). The next issue with gas is the bit about inboard engines being like riding around with bombs aboard. Yes, gas fumes are highly flammable, and diesel fuel is not. That is why all inboard gas boats are equipped with blower systems. Additionally, CAYUGA is equipped with a Fireboy fire suppression system that is designed to go off if a fire is detected.

Going back to the blowers, when Holly was a young girl aboard boats powered by gas inboards on the Finger Lakes with her parents, her dad had a simple saying. It is simply, "Begin with Blowers". We have a checklist for engine start-up, and after the sea strainer seacocks get opened (that always get closed when the boat is not in use), belts, fluids, and hoses checked, next is to switch on the Fireboy system along with the blowers.

twin 454s marine power

We regularly inspect the system and make sure the blowers are working and vented correctly. They are kind of noisy devices themselves, so it would be noticeable if they quit. In any event, with proper care and use, inboard gas engines are not, nor should be, bombs aboard, ready to explode and burn up the boat.

A big part of the decision between gas and diesel is the intended use for the boat. CAYUGA is a day boat with a limited range. She is somewhat of a "creek cruiser" and not a long-range cruising boat. Yes, we might extend our range with diesels, but that is not extremely important.



Finally, as Jarvis mentions, there is a significant cost difference between gas and diesel engines. We have been looking into options for repowering; the 30-year-old big blocks are getting to the end of their useful and efficient lives. It seems that repowering with remanufactured small block (same horsepower) engines, transmissions, and v-drives will cost far less than to repower with diesels. (I've done the research if you're interested in contacting me for some numbers.)

In closing this one out, we agree with Ole Jarvis and love the sound and fury of the big twin gas engines. We always "begin with blower" and don't shut them off until the engines get turned off. You'll hear us coming! Safe boating – with whatever powers your boat.

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