GM LS1 for marine use

Here comes yet another auto engine marinization thread...

A little background first:
I currently own a 32' marinette flybridge express, docked in salt water in Ft. Lauderdale, FL. For those not familiar with Marinettes, they're mostly aluminum hulled cabin-cruisers that were popular in the 70's and 80's. Mine is a 71 model. It's since been repowered with mercruiser 454's, which are major fuel hogs.

I am amazed at the amount of rust that has shown up on the engine and transmission since I bought it last december. The boat was a fresh water boat from tenessee until I purchased it.

Ok I could go on and on with the background, but I'm gonna cut straight to the chase.

I want more speed and better fuel economy. The 454's are around 93 models, are carbuerated and rated at 350hp. There's nothing wrong with them, they're just gas hogs. I hope with the smaller, newer, lighter, and EFI engines, I can pick up a good deal of fuel economy. In all reality, I'll probably never get back the money in fuel savings that it's going to cost to do this, but this is mainly just something that I want to do, and it will extend the range of the boat.

I've had quite a bit of experience with GM's LS1 engine, and feel it is a good, solid engine. It's all aluminum, EFI, and puts out a good amount of power(320hp/330 ft lbs IIRC)

I've read the threads on auto engine marinization, and want to bounce a few things off ya'll to make sure I have everything covered. The engines will be fresh water cooled, which I think eliminates a majority of the problems there. I'll still replace the gaskets and freeze plugs with marine versions to protect from saltwater/air outside the engine. Stainless hardware will be used where possible and appropriate. Oil pump will be replaced with a high volume pump, and an oil cooler will be fitted. Cam will be changed to something appropriate for marine service. Ignition protected components will be used where appropriate and required. Since the LS1 is a coil-per-plug engine, no distributor is used. I'm knowledgeable about programming the LS1 computer, so the fuel and timing curves will be adjusted to something proper for the cam and marine use. The fuel system is already returnless, and of course, there is no carbuerator or mechanical fuel pump to worry about. The engines will be run with 1.5:1 reduction transmissions to allow for a more efficient prop. I expect a cruising RPM of 2500-3000, with a redline of 5000rpm. If possible I will try to find/make/have made to have counter-rotating engines, but that may prove to be more difficult than it's worth, since it seems I'm venturing into mostly uncharted territory.

My concerns are:
Exhaust system: I have not been able to find anyone that makes a marine exhaust manifold for an LS1. For the best results I'd also like to keep the o2 sensor, which is going to take some work. My only solution I can see is to use a tubular header automotive-type dry exhaust manifold, routed through metal pipe until it gets to a point far enough away from the engine that water can be introduced without affecting the o2 sensors. The dry portions will be wrapped with insulating material, and possibly be wrapped with tubing with water circulated through the tubing to keep engine room temps down.

Durability:
I don't want to spend all this time and money, only to find I've burnt a hole in one of my pistons after an hour of WOT use. It will probably just take time and trial/error to determine how hard I can push the engines. I've run one of them in an auto setup under 100% load at 4500 rpm for 14 hours with no problems, not even cooling. I would think this would give me the green light for WOT marine use, but maybe not.

This is a twin engine setup, so a single engine failure won't present a particularly dangerous situation. The boat will be used mainly for near-shore, pleasure diving(under 10 miles) operations, with the occasional(1-2 times/year) trip to as much as 100 miles off shore(bahamas/bimini), although I'll probably never be more than 40 miles from land of some sort(It's 60 miles form Ft. Lauderdale to Bimini). But that's still a long way to swim.

Electrolysis from the aluminum won't be an issue, since the boat is already aluminum, it's protection system should protect the engine as well. As an added measure, the engines will be electrically isolated from the shafts, props, and hull. Separate sacrificial anodes will be placed in the cooling systems.


Is there anything I'm leaving out, anything I haven't thought of that may bite me in the *** later? I'm mainly concerned with the exhaust system, I'm not entirely comfortable with a dry exhaust system in a confined engine compartment. I think the rest should be fairly easy.

open to any suggestions, comments, etc...
If you think I'm just plain stupid for even considering it, please tell me, and explain your position.


thanks,
daniel

The cam problem may not exist if the cam bearings are the same size and location as other Chevys and Distributor gears?. Gonzo and others can answer that.-------------------Computer controlled engines are the best on mileage. There are some comp. chips that can be reprogramed just for mileage. Hot rod web sites could help. So can any NASCAR racing team if they have the time, or they will probably steer you to a good company.----------- Your concerns seem to cover most of the bases. Real problems are good companies to help you pull this off. ------If you have the money?--------------- Have each complete ready to run engine run on a DYNO TEST to get a hard print out of the fuel efficiency and horsepower curves. It will be the best spent money you can do. A really GOOD dyno tester has temperature probes in EVERY exhaust header pipe. Can pick out weak or erratic valve springs or plugs. The engines will be better than new then. You can have thm run them at WOT for any load or hours you can afford. The tests catch a bad oil or cooling system also. DYNO IT.

I think you are taking a bad idea and making things worse. The Marinette was a light weight aluminum boat when in stock setup would do 40+MPH with good fuel economy. My single engine model topped out @ 32MPH and got between 5 and 7 GPH cruise. I do think the 454s were overkill. The weight alone would have scared me off. The local engine shop just built me a new counter rotating engine, 350 Chevy, with a custom ground marine cam. The package was $2500 total with Dart Iron eagle heads. I think a pair of standard fuel injected marine small blocks will be all you need. If you feel a need for speed have a pair custom built that are designed to run blowers. A vortec/paxton style matches a boats needed power band perfectly.

There are alot of other things that could cause you problems ut the exaust is no big deal, CMI headers W/a bung installed for the o/2 sensor will work fine as long as you dont run a cam w/too mutch exaust valve overlap. That way you can run wet exaust all the way out.

O2 sensors don't work well in a wet exhaust; they give false readings. If you do an exhaust with a water jacket, the sensor will be too cold to function. You can get a standard marine 5.7 (350) GM that puts out 320HP or an 8.1 that weighs 75 lbs more at 420HP. I believe it will be cheaper than fabricating parts and experimenting. However, if what you want is to tinker, I'm interested in finding out how it went. Good luck.

woodboat said:

I think you are taking a bad idea and making things worse. The Marinette was a light weight aluminum boat when in stock setup would do 40+MPH with good fuel economy.

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That's what I'm trying to recover. If this boat would do 40, then I'd be tickled pink. It has quite a bit of extra weight in it now. a 300lb generator was placed in the rear hold. An A/C has been added, as well as a hot water heater. The rear deck has been encapsulated in fiberglass and the hatches alone seem to weigh about 150lbs each. When I take it diving, there's sometimes 1500lbs worth of tanks and gear alone, plus the weight of 6-10 people on board. Not to mention whatever extra weight the 454's are over the original 318's. I'm also considering an inverter and a couple extra batteries to handle smaller loads like the fridge and microwave without running the generator.

The boat is being hauled and I intend to completley rebuild it. I'll be replacing the rear wooden deck with an aluminum one, as well as the floor in the cabin. I'd like to add at least 200 gals of fuel capacity to make it a decent offshore boat. There's some sites 80-100 miles off shore in the gulf I'd like to be able to round trip, possibly staying out a day or two before coming back. I talked to a guy that repowered a boat very similar to mine with Marine power carbuerated 350's and topped out at around 35mph. I'm not really interested in going much over 40, as I hear these boats are hard to control at those speeds, and are really just plain scary. Right now I can suck a 100 gal tank dry in 2 hours at WOT and 27mph. My priorities are:

#1 reliability
#2 fuel economy
#3 speed
#4 cost to purchase & maintain

A EFI 350 was my second choice, but I opted for the LS1 b/c it's lighter, which will help offset the weight of the generator and extra fuel. I'm familiar with it and can fix just about anything that goes wrong with it. It seems reliable and has been a good engine for me in the past(as has the 350). And it's aluminum, which means it's not going to rust if a little salt water gets on it (big plus) I see several of them on ebay for < $3000 with a nifty, useless 4L60E tranny. I don't want to put a blower on them for reliability concerns.

If your interested, look at the pictures athttp://www.uwcorp.net/boat. There's a few of the 454's in there, they had to cut through the bulkhead/firewall to make room for them.

gonzo said:

O2 sensors don't work well in a wet exhaust; they give false readings. If you do an exhaust with a water jacket, the sensor will be too cold to function

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I knew that the o2's wouldn't behave properly in a wet exhaust, which is why I was eyeing a dry/jacketed system. If I had to jacket the exhaust, I planned to use heated o2 sensors. They should reach the proper temperature regardless of the exhaust temperature.

Thanks for the suggestions everyone, the more I can figure out on paper now, the less I'll have to spend later. And of course I'm open to more.

daniel

Just because it is alminum doesn't mean it is OK to splash salt on it. The aluminum alloy is different on your Marinette. It is specifically designed for use in marine hulls. For reliability the iron engine and heads is the way to go. Years ago when my 1989 Mustang was brand new I replaced the computer system with an Accel/DFI unit. This had the ability to eliminated the O2 sensor if desired. It relied on M.A.P. (Manifold absolute pressure) for calibration. It also had timing control and retard on boost. I had a turbo charger that made 9 P.S.I in fifth gear. After 100,000 hard miles my friend took the stock engine out as it surely had lived a hard life. When we opened it up it was perfect inside. No sludge in the pan, no ridge on the cylinder walls, same compression, no appreciable bearing wear. I have since read an article by B&M claiming that a blower extends engine life. The theory is that the pistons don't change directions as much as the intake charge doesn't have to be pulled. Anyway they make blowers so take it with a grain. My experience was that although the extra power broke lots of other things the turbo did not reduce the engine life.
I still think EFI cast iron small block and lighten the load as much as possible.

I'm not familiar with heated O2 sensors. Do you have some info?

Actually why can't you drill thru both walls of the water cooled header and have a double walled O2 probe installed? Outer tube is welded to the header tubes for water sealing. Inner tube has a standard O2 sensor threaded well that is welded to the inside hot exhaust pipe. Piece of cake for any good metal fabracator.

I could be wrong but I think an O2 sensor is virtually worthless in a marine application. The systems I've used go into an open loop condition when throttle is pushed past %50. Mine used the MAP sensor for that. They need to be very hot as we all know. Marine engines typically have a 160 Thermostat. Most O2 sensors do not funtion properly at this temperature. Then you are talking hooking it to a wet exhaust and for what? An O2 sensor helps emmisions at idle and part throttle immensly. In a marine application my opinion is that it is more trouble than it is worth.

The "heated" O2 sensors I have seen simply have an additional wire running to them.

Why can't a computer compute fuel mixtures at WOT? Road racing cars do. Fighter jets all do. I am old. What am I not grasping about sensors and ECM's?

I never said it couldn't compute there are just other sensors besides O2. You have throttle position, MAP or Manifold Absolute Pressure or the most popular Mass air flow. You don't need to know oxygen output to know how much fuel to dump in there. All I said was that O2 sensors are useful for idle smog emissions and part throttle tweaking. My computer system would only stray like 1% from my preprogramed fuel curve based on input from my O2. That is why I spent over a week tweeking my fuel curve to get it right so that for the most part the O2 was irrelevant. Given that I would err a little on the rich side in a high load situation like a marine application I would not be too concerned about the O2 level. This system is speed density and doesn't use an O2: http://store.summitracing.com/defau...239+400178+4294853151+4294853150&autoview=sku

This holley marine unit does include one http://store.summitracing.com/default.asp?target=egnsearch.asp&N=400178+310089+115&autoview=sku

I am sure they have some input about O2 choice and placement.

cyclops: if you cool down the exhaust the sensor doesn't work. Depending on the model they need to be at 350 degrees F or more.

gonzo said:

I'm not familiar with heated O2 sensors. Do you have some info

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They're used in most, if not all, modern O2 sensor implementations. There is about a 10 amp heater circuit in them(4 wire sensor) that is used to bring the sensor to operating temperature when the engine is first started, before the exhaust has time to heat up. It let the engine go into closed loop sooner than it would otherwise be able to. In an automobile application, after the exhaust reaches it's operating temperature, the heater circuit doesn't do anything, but I believe it is left on the entire time the engine is running, but I'm not certain.

cyclops said:

Actually why can't you drill thru both walls of the water cooled header and have a double walled O2 probe installed?

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That's one of the methods I was thinking. A standard jacketed manifold could have a hole drilled and a bung welded into it for the o2 sensor, as long as you keep the water(and steam) far away from the o2 sensor.

woodboat said:

The systems I've used go into an open loop condition when throttle is pushed past %50

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You know... I think you're right about that. Now that I think about it, I spent hours adjusting the fuel tables on my LS1 to get better WOT performance. I'll have to do a little research on it. If so, then I would only need an o2 sensor temporarily for the initial tuning.

Cyclops - The way modern ecms work is they have a table that they use to calculate how much fuel to inject based on several sensor inputs. The mass air flow sensor tells the computer how much air is coming in, and it caculates the proper dosage of fuel to get a good mix. The MAP sensor was used in the past, and the computer used vacuum to determine how much air was being ingested. When the system is in open loop mode, it ignores most of it's sensor inputs and uses solely it's programming to determine how much fuel is needed. This would be fine if air were the same everywhere, but just as a carbeurator needs adjustment at higher altitudes, an EFI system does also. This is where the o2 sensor comes in. It gives the computer an idea of how lean or rich the engine is running bases on the amount of unused oxygen in the exhaust. The computer then makes adjustments to it's base programming to compensate. Other conditions could create a lean or rich situation also, but I think this is the most common.

Most newer cars also have a second set of o2 sensors behind the catalytic converters that are only used for emissions. They're used to determine when to switch the AIR pump on and off, and when to throw a code if the catalytic converter(s) aren't working properly.


So... woodboat... I think you've talked me out of an o2 sensor, now if you can just talk me out of an LS1 you'll save me alot of money. My boat will always be at or very near sea level, so field adjustments to the fuel curves shouldn't be necessary... I may still provision for one to be used during tuning, or swap a set of dry headers in temporarily while everything is being programmed.

On a side note, I'm a little concerned as to how well a MAF sensor will behave in a marine application. I can keep salt water out of the intake, but I dunno how they will handle the moist, salt air.

Anyone know how much a sbc block weighs?

This page list it at #525 assembled, they list the LS1 at #397 so you would save roughly 125 LBS per engine. http://members.tripod.com/~grannys/rx7engineselectioninfo.html I carried mine on the boat with a friend and a 2x4. I think you need to purchase a marine Injection kit and use whatever sensors and instructions that come in the kit.
My mustang ran GREAT on it's speed density system. I had a 2 bar sensor so that it could read boost. I retarded timing down to 20 D when on boost. I remember having 144 grids and the engine spending all its time in half that. The big down fall with speed density is any modification and you need to go back in and reprogram the fuel curve. Because it was a turbo charged engine full power runs were unaffected, or at least seemingly, by changes in air. Also they do make stand alone sensors that help with tuning. I used one in my friends mustang, he had more money than I. He has the same Accel injection but his motor is more serious and he uses a paxton Novi 2000.


What kind of props are you swinging? My marinette had 14X11. I noticed that with a light load it would fly but if I put a lot of weight, 12 people, that it would wallow and needed a lot more power. The hull didn't seem to have much lift.