Marine vs automotive application for engines - Team Camaro Tech
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post #1 of 11 (permalink) Old Sep 11th, 12, 09:15 AM Thread Starter
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Marine vs automotive application for engines

I know nothing about power boats.
In what ways would a 350 for a marine application differ from a 350 for an automotive application?

Specifically, cam, carb, clearances? etc.

Now and then I have heard of someone running a "marine application" cam in a car. What would that get you?

I have observed that any parts that say "marine" on them seem to be about 2x more expensive on ebay.

Thanks,
Tom

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post #2 of 11 (permalink) Old Sep 11th, 12, 10:13 AM
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Thumbs up Re: Marine vs automotive application for engines

Most modifications for "Marine" (USCG) approval pertain to containing/controlling fuel vapors from the various components and prevent them from permeating the enclosed (usually) engine compartments and causing an explosion hazard.
Simple modification like plumbing the 'vent' on the fuel pump (mechanical) to the vent bowl of the carb to route those vapors into the carb to be burnt vs. letting them settle into the bilge (bottom of boat to you Landlubbers) ...

The "Flame Arrestor" used in place of the normal Air Cleaner serves a similar purpose - in the case of a Back-fire through the carb the 'arrestor' will suppress enough of the actual flame to prevent ignition of any vapors present in the engine compartment.
This - Click image for larger version

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Same goes for 'Flash-Suppression' from electrical components like Dist., Alt/Gen, and Starters.

Internally, there are few if any differences in a 'marine' engine build vs. a 'street' engine build to me, but I do select alternate components in many just to assure reliability for continuous high-load/high-RPM operational cycles.
Street engines go through many RPM and load cycles in a given cruise down the street.
A marine engine goes from idle to WOT quickly and the load increases throughout this transition from full displacement of the hull to 'planing' of the hull at operational speeds.
This load stays almost constant throughout the operation of the boat at speed - varying slightly during cornering and wind/wave conditions ...

"Marine" cams normally have 'gentler' ramp profiles, moderate overlap and design for smooth torque curves from off-idle to @5~6K RPM range.
These are actually very good profiles for many 'street' performance engines and give excellent torque response and very long service life - but don't tell everyone this or some of will lose our advantage ...

And 'Marine' parts are almost always more expensive than "normal" car parts
But if you do some checking and carefull sourcing you can find some very good deals on most of what you need.
One of my favorites for common parts is - http://www.marinepartssource.com/
I source EFI pumps and other pretty pricey stuff from them quite often and they will match/beat any one's price.
[ps: they're having a sale on gear-drive starters right now ]
Another is 'Skidim' - http://www.skidim.com/ Lots of parts for my particular boats at very good prices ...
Most of the rest of what I need comes from Summit - no really, they carry or can get just about anything I want

Now 'marine' EFI and Electronic engine controls are a w-h-o-l-e different animal ...

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Last edited by Vintage 68; Sep 11th, 12 at 10:28 AM.
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post #3 of 11 (permalink) Old Sep 11th, 12, 10:34 AM Thread Starter
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Re: Marine vs automotive application for engines

Thanks John. I knew this would be right up your alley!
Can you give me more detail about the cams? Some numbers maybe for example because what you describe sounds kind of stock-ish or RV no?

'67 rs - ordered new by my Grandfather
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post #4 of 11 (permalink) Old Sep 11th, 12, 10:36 AM
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Re: Marine vs automotive application for engines

A lot of times a "marine" engine is not even ran in a boat. They are also used as irrigation pumps for farming applications and often run on propane. Many do not have accessory holes in the heads and there are no vacuum ports in the manifold or on the carburetor.
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post #5 of 11 (permalink) Old Sep 11th, 12, 12:02 PM
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Thumbs up Re: Marine vs automotive application for engines

Actually the cams (GM OEM/Mercury Marine and some aftermarket) are usually pretty 'RV-ish'/truck in their grinds
And some GM 'Marine' cams are also found in production BB GM trucks

You going for TORQUE with most marine builds (HP drags it's sorry arse right along with it at the higher RPM's ...).
So you tend to pick cams with higher duration and longer valve events than you normally would find spec.d for a performance street engine.

So if you take a 'street' 454 (flat-hydraulic) car/light duty truck cam like the #353040 and compare it to a GM 'marine' 454 (f-h) cam like #3904359 you get specs like this;
#3963544 = (I/E) 210/213 Duration - .440/.440 lift - 113 LSA
#3904359 = (I/E) 213/217 duration - .460/.480 lift - 114 LSA
Not a huge difference - but compare the lobe profile and you'll see much slower and 'pointier' lobes on the marine cam vs. the street unit.
So the marine cam picks-up and sets-down the valve at a much slower rate vs. others and helps contribute to long service life under higher RPM and Loads found in marine use


Oh, and I haven't seen, worked on or bought an 'Industrial' BBC, SBC, BBP, BBF or SBF in 20 years that had a different amount of accessory mount holes, or lacked any vacuum or other service connection not found on a 'Car' application
Maybe many moons ago ... but not now - you figure the cost of a 'special' casting would out weight any advantage of not having the same castings anyway ...

You will find different treatment of a given part vs. a 'car' application.
There may be a plug or cap over a hole or port or even a fitting drilled into a given part to tap for water circulation or ??? - but those are installed by the sub-contractor that prepped the unit for sale to the end user.
Indmar/MerCruiser/Ilmor/PCM/Crusader/PowerTech/Hardin/et-all ... each prep a unit to the end users needs from a production GM/Ford/Iveco/whatever furnished engine assembly.
The GM assemblies are built and dressed right alongside their 'car' cousins

And don't tell anybody that that old combine you see sitting a field somewhere could have a BBC in it - I'd never find a cheap one again

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post #6 of 11 (permalink) Old Sep 11th, 12, 06:48 PM
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Re: Marine vs automotive application for engines

Thanks for the info, John. Seems like whenever my '88 Dually BBC goes in for overhaul, a long time from now, it only has 79K miles, the 359 cam would be a good step-up and be ECM compatible, ie, under 220 duration and 114 LSA for good idle vacuum and work with stock springs.

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post #7 of 11 (permalink) Old Sep 11th, 12, 07:18 PM
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Re: Marine vs automotive application for engines

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Originally Posted by Vintage 68 View Post
And don't tell anybody that that old combine you see sitting a field somewhere could have a BBC in it - I'd never find a cheap one again
And if it's old enough - it might have THE ORIGINAL BBC in it - a 348. These are also found on some farm implement "choppers".

68 Camaro SS 396 - 468 BBC now, M21, 12 bolt 3.73 coded housing but w/ 3.31 gears.
Looking for 68 Camaro with body number NOR 181016
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post #8 of 11 (permalink) Old Sep 11th, 12, 07:36 PM
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Re: Marine vs automotive application for engines

A couple of things I have heard over the years about marine engines.

Yes, I know this can get me in trouble. But maybe John can shed some light here and tell me if this is fact or fiction.

Some marine applications turn in the opposite direction, used if there are dual engines.

Supposedly the salt is very difficult to get out of the engine. True or not so true?

Hey John, you wouldn't happen to know a guy by the name of Jack Bystrom, wouldya?

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post #9 of 11 (permalink) Old Sep 11th, 12, 08:16 PM Thread Starter
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I was thinking about an opposite rotation example also. It must be to balance the torque. I imagine it requires a different cam and dist than a normal clockwise rotation engine, correct?


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post #10 of 11 (permalink) Old Sep 12th, 12, 10:00 AM
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Thumbs up Re: Marine vs automotive application for engines

Quote:
Originally Posted by Eleanor's Nemesis View Post
A couple of things I have heard over the years about marine engines.

Yes, I know this can get me in trouble. But maybe John can shed some light here and tell me if this is fact or fiction.

Some marine applications turn in the opposite direction, used if there are dual engines. ...
Quote:
Originally Posted by Melrose RS View Post
I was thinking about an opposite rotation example also. It must be to balance the torque. I imagine it requires a different cam and dist than a normal clockwise rotation engine, correct?
...
Well, in the words of the late-great Mr. John Wayne - 'Now that ain't exactly true'

Yes, counter-rotational engine assemblies can be common in some marine applications.
It is done for several reasons;
* to counter the rotational torque of the other engine(s) used in the unit
* change the reactionary rotation of the hull from the propeller design
* match the design of the final-drive system on the prop. rotation
* just because ... I've worked on a few older boats with CCR and really couldn't figure out why they used it

CCR can be used to counter 'another' engine - but then it again it is common to find a single engined boat with a CCR (LH) engine. Again done to change effect on handling of the craft for most applications.
I can only think of one manufacturer that was still using a CCR unit from the factory on their ski boats - that would be "Correct Craft".
If you've driven a boat much you would be used to the fact they turn (and back) much better one direction than the other - no use trying to back a vessel out of slip the opposite direction of the prop rotation, you won't get far - or at least where you wanted to be ...
With modern final-drive system the rotation of the prop(s) can be set-up in the gear box - so there's no reason to modify or change anything in an engine system to turn a different way from CWR (RH).

And a CCR engine does not take a special cam, distributor, oil pump or other rotational part for 90% of the applications.
All that is done to get the desired rotation is to drive the cam from the crank via a 'reversing' system - such as a direct gear set driving the cam vs. a chain on a standard chevy engine.
If a stock design cam is used, the firing order is changed to fire the engine in reverse order vs. the 'normal' GM 1-8-4-3-6-5-7-2.
It is also common to find the cam design 'reversed' to allow the desired rotation - depends on the manufacturer and needs of the power plant.
The starter also is of course 'reversed' so it turns the engine in the correct direction

But, in many applications, it's easier on performance units to just turn the engine around and drive from the front of the crank - does the same thing without all the extra hassles

Quote:
Originally Posted by Eleanor's Nemesis View Post

Supposedly the salt is very difficult to get out of the engine. True or not so true?
...
Not necessarily true ...
Most modern dedicated 'Salt' water applications now use a "Closed" circulation system with 'anti-freeze', just like and automotive application.
These system involve a water-to-water intercooler and circulate 'raw' water through the cooler to exchange heat from the closed system coolant.
This makes adapting modern EFI and aluminum component engines much easier, without the fear of corrosion eating the system in a few years ...

It's important to understand that dedicated Aluminum components made for 'marine' applications are usually "Hard Anodized" internally, so any contact with a corrosive medium (salt water) will have minimal effect on degrading the internal aluminum surfaces.
There have even been attempts to use PTFE ('Teflon') based coatings on internal passages and parts to retard corrosion effects - expensive and easily damaged if not careful, but very effective in many cases.

And sorry, I don't know 'Jack' - should I ()
Is he into boats, engines or marine builds?
I don't race anymore, so I'm not up with some of the folks that still do

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Last edited by Vintage 68; Sep 12th, 12 at 10:14 AM.
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post #11 of 11 (permalink) Old Sep 12th, 12, 10:09 AM
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Thumbs up Re: Marine vs automotive application for engines

Quote:
Originally Posted by Everett#2390 View Post
Thanks for the info, John. Seems like whenever my '88 Dually BBC goes in for overhaul, a long time from now, it only has 79K miles, the 359 cam would be a good step-up and be ECM compatible, ie, under 220 duration and 114 LSA for good idle vacuum and work with stock springs.
yup, that is a great 'towing' cam for BB's
Lots of low~mild grunt and still some extra zing when you begin winding it out

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