Marine Power 454 gas engines

[WayoutMatt]

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.

 

[rslifkin]

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).

 

[psneeld]

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.

 

[rslifkin]

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.

 

[WayoutMatt]

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).

 

[WayoutMatt]

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!

 

[rslifkin]

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.

 

[sunchaser]

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.

 

[rslifkin]

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.

 

[psneeld]

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.

 

[rslifkin]

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.

 

[sunchaser]

RS
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.

 

[kthoennes]

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.

 

[hfoster]

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.

 

[rslifkin]

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.

 

[hfoster]

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

 

[rslifkin]

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.

 

[sunchaser]

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.

 

[Blissboat]

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

 

[psneeld]

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.

 

[Art]

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.

Great discussion on this thread about gassers... I appreciate gassers' capabilities, economy [in and of many sorts] as well as ease for maintenance and repairs - on all levels during ownership.

454's are a brute! Well cared for [as has been documented in posts here] they will last a long, long time. I've got an orig 1995 tbi 454 in our Tiffin Allegro RV Class A motor home... good, strong gal!! love it!

In our 1977 Tolly I'm running couple of original 1977 350 cid 255 hp Mercruisers. Port had full rebuild 16 yrs ago; stbd had complete top end at same time. These little baby's are relatively economical and sweet/easy to deal with. At just below hull speed, i.e. cruising 6.5 to 7 knots [7.58 is calced hull speed] we get between 2 and 2.5 nmpg [depending on load aboard]. Full plane at 16 to 17 knots = 1 nmpg. WOT at 22 to 23 knots = OMG nmpg! LOL

I also have a screaming 1985 350 cid 325 hp engine in my 1985 1 ton, 4wd, 4 spd, stick transfer case, lockout hub, dual exhaust truck... love it! She gets oil change every 3K miles, tune up every couple years - and... that's it!

Then there's my beloved original [rebuilt and mildly hopped-up at 125K miles] 430 cid, 400 hp,, 500 fpt, 10.5 to 1 compression ratio beast of a muscle car engine in our 1967 Buick Wildcat - Hwy Cruiser! Love to hit passing gear next to Mercedes and Porsches! Rochester Quadrajet Carb has oversized everything inside it - roaring sound is awesome... acceleration impressive. Screwing around with youngsters in their "tiny" rice eating cars while shooting out from stoplights is great fun too. I've always gotta be careful to not peel too much rubber!

And... For added input on gasser engine longevity: Our 1975 Crestliner tow behind runabout has its orig 1975 Johnson 50 hp o/b. that still runs super sweet!

Don't get me wrong... I like diesels too. However, IMO... everything should be powered by what makes it easiest and least costly to deal with!

 

[Turtle Blues]

Going to quibble about terminology a bit. believe that mainship is semi-displacement and with those engines will get up on plane if you want to burn 35 gph plus.
it is a great boat and will certainly cruise trawler style at a more economical rate certainly the 8kn range if that is your preference.

 

[psneeld]

Early in the thread semi-displacement was the descriptor..,.quickly scanned all the posts, not sure where it was called anything else.... could have missed it though.

 

[kthoennes]

Well, our Mainship is semi displacement and even with the 454's screaming, it's still a pig and will not plane. Originally spec'd props. There are trim tab switches at the helm and when we took it for a sea trial, I operated the switches to see if I felt any difference. Nope, couldn't feel a thing. Turns out when we pulled it, the helm was configured with switches but no trim tabs had ever been installed. Probably no point. But fine with me, we run it like a fd trawler anyway

 

[Turtle Blues]

LOL
I made that distinction because I unintentionally insulted someone who has this setup by referring to it as a trawler. He assured me that it was not by putting it on plane.
Yes, it definitely used trim tabs, probably 4 sq ft total to get there but it certainly did.
I am trying to recalculate operational cost now that gas and diesel differential has been more than reversed. Seems that the diesel may still see an advantage at the higher speed range but at the low speed range cost per knot is much closer than before the price inversion.

 

[ranger58sb]

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.

Didn't know Mainship ever made a 34 "trawler" with twin gas engines.

Their original 34 was a single diesel, starting with Perkins and later including a Detroit Diesel 4-cycle 8.2T.

They made a 36 and/or a 40 "trawler" and I think that was (those were) usually twin gas-powered...

Otherwise...???

-Chris

 

[hfoster]

Well, our Mainship is semi displacement and even with the 454's screaming, it's still a pig and will not plane. Originally spec'd props. There are trim tab switches at the helm and when we took it for a sea trial, I operated the switches to see if I felt any difference. Nope, couldn't feel a thing. Turns out when we pulled it, the helm was configured with switches but no trim tabs had ever been installed. Probably no point. But fine with me, we run it like a fd trawler anyway

I looked at a Mianship Nantucket 36 sedan. It had semi-displacement hull with no trim tabs on it. It had twin gas Cruisader’s 350 260hp in it.

Their thinking was, because of the semi-displacement hull there was no need for trim tabs. They only made 50 of the 36 Nantucket’s I wonder why?

If yours would not plane with 454’s I think this Nantucket would not had a chance to get up on plane with the smaller engines.

Not having trim tabs was one of the reasons I walked away however it was a nice vessel and I did like it.



https://www.hmy.com/yachts-for-sale/mainship-yachts/36-nantucket/

https://www.yachtworld.com/yacht/1988-mainship-36-nantucket-7526875/

Cheers

H.

 

[rslifkin]

In a lot of those boats, the line between SD and planing is pretty blurry. People seem to like calling any hull with a keel SD, but it's not true. My hull is sometimes called SD, but I disagree and say it's a planing hull (just a slow, draggy one that's got enough keel and rudder to handle well at low speeds and that develops handling problems if you try to push it too fast). My boat goes from displacement speeds up through a distinct bow-high plowing stage, then settles onto a pretty nice, clean plane. That's a planing hull in my book even though it doesn't have big chine flats aft and relies on huge (48x12) trim tabs to get the stern up. SD would be usable above hull speed, mine really isn't until you get on plane.

 

[diver dave]

A lot of “noise” in this thread.
Marine Power 454’s are not Crusaders.

Crusaders, when in the Gen IV big block days, used 4 bolt mains, custom U tube oil cooler, and custom exh manifolds, sherwood bronze raw water pumps.

Arguably, the best 454 implementations for a boat big block.
I ran these for a decade in a planing sportfish. The OEM iron risers last 3-4 years in saltwater. Post op rinsing did not extend. The U cooler and HE good for 10 years.

Propped for 4200 rpm at WOT, i cruised at 3200 at 12gph each. With my flowscans, I plotted exact burn at total rpm range, one and two engine ops. I could approach 3nm/gal with one engine at 1500 rpm. But , I never ran there. I had also swapped the carbs and intake manifolds with a Carter/Edlebrock marine set-up.

On the gas safety thing. Beyond the engines, tanks and filters can leak. Be diligent with fume detectors, powered ventilation, and your nose. I ALWAYS sniffed the outbound vent air before cold and hot startup.

It was a benefit to be able to totally overhaul these engines, even under my mango tree at home. Using a real shop for borings only.

My advice, run the 34 for a while, if U like the boat, put in a couple NA 30 to 40 hp diesels.
You should be able to use much of the existing 4” exhaust system, tanks, and shafting.

 

[Art]

While Cruising Along... in clam waters... 6/20/22 on an 80 mile jaunt from SF Delta Freshwater marina to SF Bay saltwater marina [full gasoline, water tanks, all tools and 3 adults aboard]:

I played with our Tolly's trim tabs.

Doing 7 knots [1/2 knot under her 7.58 calced hull speed] - Tabs would definably but only slightly alter the trim of hull through water. Speed shown on GPS was not affected so as to notice.

Doing 16 to 17 knots on full plane - Tabs had noticeable affect on hull trim. GPS speed would alter by 1/2 +/- knot. Trimming her slightly bow up was the magic spot.

Doing 19 to 20 knots [for a brief stint] - Tabs had same overall affect on trim and speed alteration as at 16 to 17 knots. Didn't bother to push her twins up to WOT, i.e. 22 to 23 knots... cause, IMO... that high rpm/speed in a 45 year old boat with 45 year old [350 cid / 255 hp. Mercruiser] engines is to be utilized only for emergency conditions.

Vast majority of the time I kept her just below hull speed. At end of 80 +/- mile trip her tanks each had exact same 78.5 +/- gallons remaining. I felt really good about that because that meant that both engines [I keep them rpm synchronized] are running equally well; as I have them each limited to drawing off their own tank. Another item that pleased me was fluid remaining in overflow coolant tank of each engine was exact level as at trip beginning and oil levels same too! I keep these twin babies well tuned, lubed and cooled.

And, yes: I can get fuel measurement that close in my gas tanks with torpedo fish-weight as weighted-end of drop string that displays exact level [number of inches] of fuel in tank that I multiply by gallons per inch the rectangular tank holds. In this case: The weighted drop string measured 17.5 inches fuel remaining in each tank X the tank's 4.5 gallons per each inch of fuel level = 78.5 gallons. Not much different than a straight stick test. Reason I use end weighted string is some twists in access that stop a stick from entering.

Soooo... for calculating fuel burn to miles traveled: 80 mile cruise began with two topped off 100 gal tanks [let's say 98 gallons +/- each] = 196 gallons. Minus 157 gallons remaining = 39 gallons used. 80 miles -: 39 gallons = 2.05 miles per gallon - or - 3.4 gallons per hr at 7 knot cruise. X today's price of $6.00 bucks per gallon = $3 per mile or $20.40 per hr. For a grand total cost of 39 +/- gals used = $234 to move a 21K lb cruiser 80 miles through the water wile experiencing a "Priceless Day" on the bimini covered flying bridge of a truly comfortable 1977 Tollycraft Tri Cabin Pleasure Craft!!

We Simply Luv It!