Modern 350 Marinizing

Yes, if the gasket is the wrong type, it will let gas through at all times. The power valve opens when the vacuum in the manifold drops below a certain level- that is the number in PSI.

 

http://books.google.com.my/books?id..._pigDg&sa=X&oi=book_result&ct=result&resnum=4

Everything you need to know should be here

 

Thanks guys

 

Reading this and other posts about the users describing what a marine engine is or isnt.
The items people list are close depending on the model.
If we talk Merc Chev V8's the stock ones are assembled by GM and have either the GM marine cam or the sellers design.
The main items I see as different to the car engine and quiet often inserted hardend push rod ends and higher quality valve springs,retainers etc and along with brass plugs, stainless head gaskets etc, and the whole electrical and fuel system.

Many of the components in the marine engines to increase reliability at sustained high revs ( although only as high as the auto engine reved at) end up in the auto stuff as and when it becomes viable due to volume.
Stock engines dont have oil coolers and if you drive at WOT in many of them the oil temp will go well over 250F so they get a hard time.
Many components can/are be re heat treated and or extra shot peened etc which would make them higher end components compared to stock and hence wind up in the marine production line. Rockers and retainers come to mind?

IF we talk about slightly higher production performance(SBC) engines like the old 280TRS , 300 and the 320 EFI Mercruiser these are very different ( and the Volvo 290) Still fully assembled by GM. These all had 4 bolt mains, bigger valve heads ( not 2.02) GM pink rods, TRW eyebrow style forged pistons ( but with fixed pins) steel cranks, heavy duty harmonic balancer, high volume oil pumps with hardened shafts, heavier pushrods, better quality valve springs, double roller chains ( on the flat tappet engines) Larger baffles sumps and main cap mounted solid windage tray.
Oil coolers (vendor supplied but always too small) aluminum inlets with bronze water crossover ( Volvo had the old70's LT1 style cast iron high rise)
Crane cams but they usually will not supply you as they OEM'd them to the vendors. But not SS exhaust valves.
Just check the parts book.

BBC
454/330 Merc read like stock 350/260, then from the old 370, 400, 420, 425, 440, 460, 500 and on also read like the above but even tougher. mostly LS7 style stuff, rectangular port heads, large pushrods in guide plates, roller rockers, very heavy valve spring sets ( like safe to 7500!), Inconel exhaust valves, custom crane hyd cams and oil coolers that are too small.
So there's thats what I've seen working on them.
E&OE other GM stuff might be altered but either I never asked or couldn't tell by looking at it.

What did I think they needed for sustained WOT...floating wrist pins, cam buttons, larger sumps with the static oil level further away from the crank, larger oil coolers but I might have mentined that but with thermostat, screw in rocker studs, pushrod guide plates, roller tip or full roller rockers ( BBC has these) balance them, blueprint the oil pump and then a std volume std pressure one will do the job. You can block off the oil filter bypass too but its there for a reason.

 

I just replaced the engine in a '98 Ski Nautique. It's rated at 320 hp and is the EFI-equipped variation known as the Apex. It was the highest hp rated variant of the 5.7 GM engines offered in this model boat from this model year. I disassembled it prior to ordering a long block to verify that it was indeed cracked, and despite what many folks want to believe, (including the boat's owner), there was absolutely nothing "special" or "heavier duty" about it at all.

A couple of phone calls and some checking of the numbers on the original engine verified this. Except for the dedicated marine components like the camshaft/frost plugs/gaskets, the engine is a standard 5.7 Vortec.

It doesn't have *special* pushrods, connecting rods, pistons, rocker arms, etc. It didn't come down some special marine-only assembly line, from which defective or second-rate parts are rejected and sent on to be haphazardly slapped into pickup trucks.

4400 or 4500 rpm for 10 or 15 minutes at a time towing a skier or group of people on a tube might seem like it's some sort of extreme duty, but it really isn't....all things considered. If the same power plant were in my light truck, it would see duty towing, cruising, idling, etc. It would also see duty in dusty and dirty conditions, and would also be expected to perform those duties from -30F to +100F where I live. If anything, a non-marine engine would need to be built tougher to survive around here.....doing what it's needed to do.....day-in, day-out....not just on a sunny weekend.

Yes, there are plenty of extreme conditions boats can see duty in. But seeing as this is a DIY Marinizing thread topic, let's not pretend the boats people are discussing here are something they're not. If the engines we're talking about are offered already in marine applications and are found in non-marine applications as well, there's no need to make it seem like swapping a few bits from one to the other approaches rocket science. It doesn't. It's a few nuts and bolts.

Cost seems to come up frequently as well. I suppose it would be very "cost-ineffective" to obtain a standard non-marine engine and then go to the trouble of converting it to marine specs by visiting the local marine dealer and buying brand spanking new parts off the shelf at the typical retail prices a dealer needs to charge to turn a profit. I really don't think many people would actually considering approaching a DIY conversion that way though.....what would be the point? New and used parts are available everywhere. You don't need to hop in a vehicle and drive to a place that has boats parked in rows out front if you want a marine camshaft, or a set of gaskets. Do some research and see what part numbers you'll need. Disregard the "expert" advise from people that say things like *special* unless they can provide specific info as to what *special* means. You'll hear all kinds of hooey about *special* rods/oil pumps/valves/whatever, but without details and knowing for sure, well.....then just open the wallet, invert it, and let gravity do the rest.

 

Exactly,---Ive been saying this for years. In Uk 40 years ago there was no such thing as marine egines for ski boats. Most engines Ford Uk ever made found its way into a boat, the only modification would be to an SU carb.

I bought a Mercruiser 225 V8 Chev engine 20 years ago. The block was cracked , I had it cold stitched because I didnt know it was just a 305 CI chev.

I was sucked in by the American "marine" hype. I could have bought a short motor for half the cost of repair, Oh well we live and learn.

Once I found this out I enjoyed most summers bolting on manifolds, new starter motors etc etc all from the American parts store.

Now we will get-- Oh it needs a stainless marine gasket, it needs anti spark starter, It needs a marine alternator and a fuel bowl breather.

No it does'nt "need" that ---your regs in US require that.

Ive seen an outboard set on fire but never ever seen an inboard, maybe im just lucky.

 

Guys I was talking Mercrusier Sterndrives not DIY Ski Nautiques. Ski boats are not a Market Merc has much presence in.
Ski boats although do many full throttle starts dont sit at WOT for hours and over rev when jumping out of the water ( rev limiters are only a new thing)
and yes Frosty a 225 would have been a stock GM at that horespower as you said. (225's were from 1963-66 327ci. or 228 1982-84 305ci)
Too True Frosty well said "doesn't need but does to be USCG approved". The only one I would say it needs is SS head gaskets if you use it in sea water and the marine engine circulation pump, core plugs etc.
Australia had a very large DIY engine conversion business due to the fact we had all the US v8's and GM had its own Australian V8 as well. This was from the 60's and still running today for our ski boats. The US marinised engines were expensive then.
Today People are paying AUD70k+ for a imported rig now ( well last year anyway)..ouch.
Most laws in each state only made you run a flame arrestor on the carb.
I have seen plenty go bang when starting.
Never seen a proper USCG spec marinised engine go bang. Something the average faamily boater is interested in.
Aftet you see people torched in a boat you are extra careful when working on them especially in giving advice on fuel and electrical systems.

PS making a GM delco starter USCG spec is an easy as one drop of silicone in the right place.

 

FWIW, I wasn't referring to any of the accessories that are bolted onto the engine itself. If a marine application recommends a USCG approved starter/ignition system/carb/whatever, then I wouldn't recommend doing without it. I was talking about engines, as in.....the engine itself. There's just as much, (if not more), confusion and lack of clear info out there about the short or long block itself, which is why I mentioned some of the terms frequently tossed around.

"It has *special* rods/rocker arms/rods/pistons/block/oil pump/valves/whatever".

Do those components exist? Sure they do. Does that mean every marine engine is built from the ground up containing nothing but these <cough> *special* <cough> components? Hardly.

Suppose a person reading this thread already has a boat and wants to "marinize" a non-marine auto or light truck engine. Just like the example Frosty mentioned with the cracked block, the boat owner simply wants to obtain and install a replacement engine. The boat owner already has the starter/carb/ignition sitting there on their otherwise unusable "marine" engine.

Why does the topic need to be muddied up with all of this nonsense about these *special* parts that exist out there, and why the *special* conditions of pushing a boat from point A to point B require these *special* parts, and using anything other than these *special* parts just might cause the boat to spontaneously sink upon contacting the water?

I think what might be going on, is that some folks that haven't dealt with anything but marine stuff are probably not familiar with the internals of a non-marine engine. If they were, they wouldn't be so adamant about the "special-ness" of the typical run-of-the-mill boat engine.

 

Actually if there IS anything different its the cam. Some high performance cams have overlap and encourage reversion which is not good on a water injected exhaust.

As well as this, a marine cam is more of a 4 wheeler cam not because of any special metals but it brings the torque and HP down to RPM that can be used best.

Then there is the distributor --if you have one that does not have vacuum advance, easy to disconnect but.

 

Yep, I mentioned the marine cam....and that's the kind of stuff I mean when I say "marinizing" the engine. Folks get spooked by the very thought that someone would consider "marinizing" a non-marine engine. They always mention the plethora of marine accessories that are bolted onto a standard non-marine engine to convert it to boat use. It seems that they fail to consider the boat owner's intent. If a person posts a question in a "DIY Marinizing" thread, it's because they want to make a non-marine engine suitable for boat use.

If the boat owner simply goes to a scrapyard and pulls a used engine out of a car or truck and drops it into place with it's original gaskets/frost plugs/ starting/charging/fuel/ignition systems completely intact, they've made no attempt to "marinize" anything, they aren't asking any questions about marinizing, and they aren't interested in marinizing.

If that same boat owner buys the auto or truck engine and asks what a comparable "marine" engine of the same make and model contains, then the actual differences should be explained. In detail. *Special this* or *special that* is all pie-in-the-sky and means nothing.

Well, 'cept of course that *special* is always harder to obtain and more expensive.

If the boat owner had his original "marine" engine pulled out and sitting next to his recently obtained replacement "non-marine" engine, it would take a half day of labor working at an extremely leisurely pace to get the job done. Throw in a few $$ for the gaskets/frost plugs/proper cam, and what you end up with is something that has fallen far short of the mythical and mysterious processes some people want to convince the masses are required to get their machinery back on the water.

 

I know this is an old thread but the biggest retardation to peoples learning on this site is the user *****!
I simply do not know where to start with this guy, my advice for ***** is to please find a blend between your substantial marine knowledge and common sense.

So many unqualified claims, such as.
Marine engines are enclosed and therefore get too hot??? They breathe and require ventilation like any other engine, ever noticed the holes in an outboard cowling?

 

I don't think he's a bad guy, and I'm sure he has good intentions, but......I also think that his experience *outside* of the boating realm is pretty limited.

Couple that with the fact that (it sounds like) he works for a dealer, and his position becomes more understandable. Boat dealers are like many other "specialty" shops in that they do one thing, and charge you handsomely for it.

So when he talks about how *special* a component is, or how there's no way to do something *for less money*, (such as DIY marinizing), he's approaching the issue from a dealership prospective. This isn't meant to be a slam on dealerships at all, but you'll pay MSRP or more for parts there, and you'll be quoted a pretty hefty amount to have the work done for you as well.

The thing is, he doesn't know what individuals out there are capable of as far as mechanical ability goes, and he also doesn't know what they have available for parts sourcing......so I really don't know how he can make any assumptions about cost comparisons between buying a marine engine versus marinizing a non-marine engine.

When customers ask me about parts and such for the industrial equipment I work on every day, I don't use meaningless terms like *special* unless the part is indeed special. And if it is, I'll explain why.

I buy lots of parts every day. I could buy the stuff from the OEMs, but in most situations I don't......because all they're doing is taking a cut. Sure, there are some parts that are made by the machine manufacturer such as weldments, but a whole lot of the bits are just pieces they sourced from another vendor. Why pay extra $$ to what's essentially a middle-man?

So when he talks about how expensive something is, he's assuming you have to go to a boat dealer to get it.

And you don't in many cases.

 

Yep

Wise words, I guess I look to threads like this for information and free opinion to help those with build ideas. I am engineer of 13 years which is not a long time I know, I'm a bit of a mad inventor as well and love to read about solutions to problems, not people saying it can't be done with NO solid evidence.
I'll cool my jets

 

Corvettes for the last few models are returnless as are ALL marine systems

 

The Ford Mustang and F-150 have had non-return fuel systems since 2008. Fuel pressure is regulated by an electronic fuel pressure sensor on the fuel rail which sends a signal to the ECU, which controls the fuel pumps (they have dual in-tank fuel pumps). There are performance kits available to convert it back to the return type fuel system when installing super chargers.

As usual, California drives emissions improvements in the automotive sector. Non-return fuel systems are mandatory in order to reduce evaporative emissions. Basically the fuel being returned to the tank has absorbed heat from the engine compartment and in turn heats the entire contents of the fuel tank, causing more off-gassing. If I'm not mistaken, gasoline powered vehicles produced in the last few years should have such a fuel system.

On another topic intertwined in this thread, some of you trivialize the USCG requirements for fuel components and engine electrical components. As with most safety regulations that at first appear silly, chances are that regulation wasn't added until after somebody died, and chances are people have died since the regulations were enacted because the regulations were deliberately disobeyed.