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Old 06-21-2022, 07:42 AM   #1
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Marine Power 454 gas engines

I have done a search but I cannot find any discussions about having Marine Power 454 gas engines on a trawler. Looking at a 34 Mainship with two of these engines. My preference is diesel just because its the norm, but I like the boat and layout. What is the opinions here on having these engines? If you have experience with them, what do you think the fuel burn would be at 7-8 knots?

Many thanks for your advice.
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Old 06-21-2022, 07:44 AM   #2
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In a 34, your efficient slow cruise speed will likely be down around 6 - 6.5 kts, not 7 - 8. With twin 454s, I'd figure you'll burn 5 gal/hr or a little less (total) in the 6 - 6.5 kt range.

As far as gas marine engines go, the 454s are pretty thirsty, but they're a generally durable engine. The primary concern is to watch the condition of exhaust components and replace as needed (water intrusion from failed risers, etc. is a big killer of gas marine engines).
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Old 06-21-2022, 07:53 AM   #3
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I ran a marine power 454 in a assistance towboat gor 15 years and probably 5000 hours under the hardest use imagineable.

Other than oil changes, 1 spark ug change, one fuel pump change, and one rusted our electronic distributer assembly and custon stainless risers....zero other maintenance.

It was in a 1980s vintage 26 foot Shamrock so expised to environmental conditions way worse than a trawer engine room.

It took everything I could throw at it for a towing/salvage boat and wS replaced after 15 years not because it needed it, we were just holding out breath for something bad and the boss got a good deal on a new, more fuel efficient engine.

That engine totally changex my mind about gassers vs diesel. Not the huge difference I was lead to believe by so called experts, readings and the internet.
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Old 06-21-2022, 07:57 AM   #4
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That engine totally changex my mind about gassers vs diesel. Not the huge difference I was lead to believe by so called experts, readings and the internet.

Agreed. Your experience is definitely proof that most gassers are killed by their owners, not worn out. Partly because the marinization (especially exhaust stuff) isn't great on many, so a little bit of neglect can easily lead to major damage. And they're often in cheaper boats, which means many of them go to worse owners.

It also helps that the basic low output 454 has proven to be one of the more durable marine gas engines. Plenty of others (including higher output variants of the 454, 502, etc.) don't tend to last as long even with good care.


Realistically, the only complaint I have with my twin 454s is fuel consumption. Modern diesels would burn a lot less. But the gassers are plenty reliable and do the job just fine.
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Old 06-21-2022, 08:02 AM   #5
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Thank you. That is all I need to know. Obviously, that is why this otherwise well maintained and attractive 1996 boat is priced the way it is.

As an aside, it seems when fuel is cheap, manufacturers put a lot more power in these semi displacement hulls because buyers wanted a faster boat. Fuel prices in 1996 were very low (adjusted for inflation).
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Old 06-21-2022, 08:13 AM   #6
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Maybe beating a dead horse, but let's say I got the boat for 20% less than a comparable boat with a diesel. That would cover the cost of a lot of gas. However, when I get ready to sell it, it is still going to get 20% less than a diesel boat, so the cost of using the boat is still much higher. Anyone disagree with this?

Thank you for your replies and knowledge!
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Old 06-21-2022, 08:16 AM   #7
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I wouldn't worry too much about the selling it later part unless you only plan to keep it for a short time. It's too hard to know what the value of a given boat will be in 5 - 10+ years.
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Old 06-21-2022, 08:18 AM   #8
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A friend had 454s in a Tolly 48. He took good care of them. At 3300 hours he sold the boat. The new owner had a pair of fresh Cat 3208s ready to drop in when the gassers had a serious issue. The Cats sat in their crates for several years as the new owners waited - I lost track after 3 years.

Matt, if you buy the boat, assuming the engines check out, do a total servicing asap for coolant, impellers, water and fuel hoses, belts, risers etc. Also, insure the fill hose to the tanks is vapor free - pour 5 gallons in each tank and give it the smell test. You can’t be too careful on old boats.

At 2500 or so RPM those are long lived engines. Once above 4000 not so, best to probe previous owner for operating history. And yes, I’ve had a 454 marine engine.
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Old 06-21-2022, 08:24 AM   #9
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Good point on the RPM thing. For the basic low output 454s (rated 330 - 350hp depending on the marinizing company), WOT RPM should generally be in the 4200 - 4400 range if propped correctly. As long as they reach 4200+ at WOT, treat 3400 as max continuous for good lifespan.
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Old 06-21-2022, 09:05 AM   #10
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Pulling a barge out of the surf and against a 3 to 5 knot current in a Noreaster with that Shamrock ....to make it to the marina, that 454 was on the pin under tremendous load for around 3 hrs and never went above 3000rpm.

That didnt affect a thing that I know of...no loss in power, no oil burning and no other maintenance other than an oil change early for the next 2000 hrs/7 years or so.

Yep diesels are great and so are some gassers. And please dint bring up gasoline and safety, it really is sad where that discussion goes.
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Old 06-21-2022, 09:27 AM   #11
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Pulling a barge out of the surf and against a 3 to 5 knot current in a Noreaster with that Shamrock ....to make it to the marina, that 454 was on the pin under tremendous load for around 3 hrs and never went above 3000rpm.

That didnt affect a thing that I know of...no loss in power, no oil burning and no other maintenance other than an oil change early for the next 2000 hrs/7 years or so.

Yep diesels are great and so are some gassers. And please dint bring up gasoline and safety, it really is sad where that discussion goes.
I'm honestly impressed that didn't hurt it. Usually overloading like that gives concern for burning exhaust valves.
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Old 06-21-2022, 09:56 AM   #12
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The 454s in their assumed use were designed for serious lugging in applications such as RVs, (Fords V10 too) towing and carrying loads. Valve seats and the valves themselves can be designed for this application. With heavy duty work planned for pickups and large SUVs the same could be said for current engine designs.
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Old 06-21-2022, 11:00 PM   #13
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We have twin Marine Power 454's in our 1996 Mainship 37. Good reliable engines for us. The only issue I've ever had was water in the gas, particularly after a winter layup, but that's not the engine's fault. Just takes a couple changes of fuel filters in the spring. They sure are big though, with I had more room in the engine bays for maintenance.

If you keep the speed slow, they're not too awful on gas. The consumption curve is ridiculous though, push it too hard and you might as well measure fuel burn in linear feet per gallon.
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Old 06-24-2022, 09:00 PM   #14
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I am coming in late on this however one thing that has not been said or asked is what kind of 454 engine are they?

I have a 1979 Chris Craft 380 (38 foot) with twin 1979 454's Crusaders 330 hp. These old Crusaders are built to last and can take a beating.

If they are taken care of, you can get 6,000 hours out of them before any major issues come up. Mercruiser 454's do not last as long, even with good up keep for some reason.

Most of them start to have major issues around 2,500 to 3,000 hours. As far as fuel burn goes, running 18 mph at 3,000 rpms, I am burning 26 gph total ( about 13 gph a side.)

The trick with 454's is get the vessel up on plain and let them cruise at cruising speed. If you kick in the 4 barrel they will suck fuel down really fast. Up to 44 gph a side. You can run slow speed 6 , 7 or 8 mph, however they really do not like in the long term.

These engines were built to run at higher rpms. The slower speeds in the long term will foul the plugs so you are always cleaning or replacing your plugs. You will know it right away when you start getting miss fires in one or both engines.

A month ago my starboard transmission failed so I ran about 60 miles on one screw to get hauled out for repair. Running 8 mph I burned about 5 gph on the port side. I would have gotten a little better fuel burn if I would had been able to run both engines may be around 4 to 4.5 gph.

So yes you can run at trawler speeds with the 454's however it's a trade off with a little more up keep on the engines.

One other thing to remember with gas power marine engines is, they are not like a car engine. I cannot remember but I believe it is something like this.

For every 1,000 hours on a gas marine engine it's about a 150,000 mile on a car engine or something like that. So on a Mercuiser with 2,000 hours on it, would be like having 300,000 on a car engine.

That is why you see a great deal of Mercuiser's starting to fail and YES even Crusader can fail at lower hours but not as much.

I have 2,200 hours on mine and they still are running really strong (knock on wood.) Keep in mine.

Vessel's with gas 454's on the average is about 1 mile to the gallon. The best I have done is about 1.5 to the gallon running 16 mph with a clean bottom two man crew and 400 gallons of fuel.

Hope this helps you out.

Cheers.

H.
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Old 06-25-2022, 07:16 AM   #15
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If you're fouling plugs running at low RPM, they're running too rich. My 454s have run for 25+ hours of canal cruising without ever getting over 1500 rpm and have had no issues with fouled plugs or anything else.

1 mpg on plane in something big and heavy with 454s is very optimistic. I plan for 0.5 nmpg on plane (17 kts) and 1.2 at slow cruise (6.5 kts). Realistically, I do a little better at both speeds, but not a lot. Propped to turn 4200 at WOT, I figure on about 5 gal/hr (total) at 1300 rpm, 30 - 32 gal/hr (total) running at 3300.

The Mercruisers often die earlier because the exhaust setup isn't as safe a design. So if the risers, etc. aren't attended to well, they suffer a watery death via the exhaust valves. Other than Crusader using 4 bolt main blocks for everything and Mercruiser often using 2 bolts blocks for the lower output engines, the internals on the 454s are pretty similar between all of the marinizers. In the 80s, Crusader had the better exhaust setup, but IMO, Merc had better ignition systems in that era. Well cared for low output big blocks (like the 330/340/350 hp versions of the 454) will last a pretty long time.

As far as engines in a 79 Chris Craft, just because they're blue doesn't mean they're Crusaders. If they're original to the boat, I'd expect them to be Chris Craft marinized engines in those years. The Chris Craft engine division is what later became Marine Power.
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Old 06-25-2022, 08:03 AM   #16
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Agree with you Rslifin on running rich to foul the plugs.

What I am saying is in the long term. If you run them year after year at the lower speed without blowing out the carbon it will foul the plugs. Plus it will come down to what grade of fuel you are running as well.

We have chatted about our boats and the hulls are the same just different layouts. Even though they almost the same they run different. If I recall right you though my RPM reading was off when I told you I was running 18 mph 3,000 rpms. I checked it and that is what I was getting.

I also ran the Serial numbers on my 454's . They are Crusaders so that is a plus for me.

I am still working my way to my home port I should be done with the trip next week. I had to stop to go to my Sister's wedding which is today.

I will keep you posted on what happens. So far so good.

I am not to keen on this guy (David) but his review was petty good and a good read.

https://www.yachtsurvey.com/GasEngines.htm

Cheers.

H
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Old 06-25-2022, 08:21 AM   #17
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Agree with you Rslifin on running rich to foul the plugs.

What I am saying is in the long term. If you run them year after year at the lower speed without blowing out the carbon it will foul the plugs. Plus it will come down to what grade of fuel you are running as well.

We have chatted about our boats and the hulls are the same just different layouts. Even though they almost the same they run different. If I recall right you though my RPM reading was off when I told you I was running 18 mph 3,000 rpms. I checked it and that is what I was getting.

I also ran the Serial numbers on my 454's . They are Crusaders so that is a plus for me.

I am still working my way to my home port I should be done with the trip next week. I had to stop to go to my Sister's wedding which is today.

I will keep you posted on what happens. So far so good.

I am not to keen on this guy (David) but his review was petty good and a good read.

https://www.yachtsurvey.com/GasEngines.htm

Cheers.

H

You're probably propped a bit differently, and your boat could also be a little lighter than mine. That would explain the speed vs RPM difference.
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Old 06-25-2022, 09:54 AM   #18
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In the early nineties the Gen V 454 redesign came out. The changes improved reliability, oil pan design, lifters, bearings and lubrication. Whether Crusader or Mercruiser the Gen V would be an improvement. In the day 454 owners, including me, liked the Gen V whether on land or sea.
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Old 06-25-2022, 10:11 AM   #19
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Crusaders may well be all that their advocates say - I don't know. But psneeld's account calls to mind a lesson that applies to all marine engines: the more often and more regularly it runs, the better. In towing / assist work, that Shamrock had to run a lot. For several obvious reasons, that ensured good engine health.

At risk of a bit of thread drift, my experience with a two-stroke 115 hp Mercury outboard drove home the lesson for me. Merc was hardly my first choice for a repower, but that particular engine was an unbeatable deal. I mounted it new out of the crate on a 28' workboat, and proceeded to run it at least five days a week, sometime six or seven days, in salt water, for the next 16 years. The boat lived in a wet slip, and since it went right back out each morning, the cooling circuit never got a fresh water flush. At the end of each day, it was just trimmed up out of the water for an external rinse with the hose. Over those 16 years, all I did was replace plugs and wires, fuel filters, a damaged lower unit, and a failed stator.

I sold that boat with the same engine on it, still running strong, and I am still shaking my head in amazement. The point is, any engine that runs a lot is at less risk of neglect and all the little insidious problems that sneak up on it as a result of just sitting. YMMV
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Old 06-25-2022, 10:29 AM   #20
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I am not sure why in the old days everyone said gassers and outboards don't live long.

Well, the 454 I ran disproved that ALL will die early.

Seems to me...even now I see waterways filled with 1980s, 1990s and early 2000s vintage outboard purring along with the owners saying parts are no real problem when recent outboards are laid up half a season waiting for parts.

Makes ya ponder a bit.
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