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1983 Mercruiser Iron Duke by Csjag
Started on: 02-28-2014 07:38 PM
Replies: 34 (2120 views)
Last post by: TopNotch on 08-09-2014 07:56 AM
Csjag
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Report this Post02-28-2014 07:38 PM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
This is probably a bizarre idea but I have an 1983 Wellcraft 18 ft I/O boat that I just listed on craigslist. It has the marine version of the Iron Duke with a twin jet Rochester carb and its rated at 120 hp and according to the sticker on it also rated for continuous use at 3700 to 4300 rpm. Anyone ever us this in a Fiero?
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Ventura
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Report this Post02-28-2014 07:50 PM Click Here to See the Profile for VenturaSend a Private Message to VenturaEdit/Delete MessageReply w/QuoteDirect Link to This Post
The Mercruiser 2.5 is a Chevrolet engine. The Fiero 2.5 is a Pontiac engine. There are no interchangeable parts and the bellhousing bolt pattern is different.
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mrfred8
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Report this Post02-28-2014 08:17 PM Click Here to See the Profile for mrfred8Click Here to visit mrfred8's HomePageSend a Private Message to mrfred8Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Ventura:

The Mercruiser 2.5 is a Chevrolet engine. The Fiero 2.5 is a Pontiac engine. There are no interchangeable parts and the bellhousing bolt pattern is different.


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Ventura
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Report this Post02-28-2014 08:26 PM Click Here to See the Profile for VenturaSend a Private Message to VenturaEdit/Delete MessageReply w/QuoteDirect Link to This Post
There is one part on the Mercruiser engine that can be used on the Fiero 2.5. The Mercruiser rocker arms and later model LS1 rocker arms studs will give you adjustable valves and eliminate the valve train noise. Valve adjustment is 1 1/2 turns past zero lash. My noisy '84 is now quiet.
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Csjag
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Report this Post02-28-2014 10:42 PM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
Ventura: will the rockers work on an 85 duke also?
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Ventura
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Report this Post02-28-2014 10:47 PM Click Here to See the Profile for VenturaSend a Private Message to VenturaEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yes........get rocker arms for an older GM inline six such as a !973 250cid truck......you can get LS studs cheap on Ebay........my "84 was unbearable but now it purrs like a kitten.
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Csjag
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Report this Post02-28-2014 10:54 PM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
how did you discover this? Thanks
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Ventura
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Report this Post02-28-2014 11:01 PM Click Here to See the Profile for VenturaSend a Private Message to VenturaEdit/Delete MessageReply w/QuoteDirect Link to This Post
I worked in the boating industry for many years. I know the Mercruiser engines very well and GM history. Owning a Fiero gave me room to experiment.
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wftb
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Report this Post02-28-2014 11:48 PM Click Here to See the Profile for wftbClick Here to Email wftbSend a Private Message to wftbEdit/Delete MessageReply w/QuoteDirect Link to This Post
the mercruiser iron duke is the original iron duke .it was one of the most reliable engines ever built .the fiero duke was a cheap low hp lighter weight version designed for the fwd gm X cars .that version is what the fiero was cursed with .if you want to put a mercruiser v6 in a fiero , get an archie v8 adapter plate .then put a turbo on and let it rip .and most of these motors are 3 litres displacement .
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wftb
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Report this Post02-28-2014 11:55 PM Click Here to See the Profile for wftbClick Here to Email wftbSend a Private Message to wftbEdit/Delete MessageReply w/QuoteDirect Link to This Post
actually i am not sure about the 3 litre displacement .most of these engines are advertised as 130 hp .i don't see a reference to engine size .
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Old Lar
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Report this Post03-01-2014 09:42 AM Click Here to See the Profile for Old LarSend a Private Message to Old LarEdit/Delete MessageReply w/QuoteDirect Link to This Post
http://imageshack.com/a/img35/9176/sx5l.jpg

This had a Merc Cruiser engine. A FOCOA show 2002
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psychosurfer
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Report this Post03-01-2014 10:22 AM Click Here to See the Profile for psychosurferSend a Private Message to psychosurferEdit/Delete MessageReply w/QuoteDirect Link to This Post
I thought I remembered a thread a loooong time back where someone was looking for a replacement 2.5 for their Fiero and people were saying to use the 2.5 from the s-10. Would that not make it the same engine, if indeed they are interchangeable? Just wondering based on the comments about them being different.
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aaronkoch
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Report this Post03-01-2014 10:50 AM Click Here to See the Profile for aaronkochClick Here to Email aaronkochSend a Private Message to aaronkochEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Old Lar:

http://imageshack.com/a/img35/9176/sx5l.jpg

This had a Merc Cruiser engine. A FOCOA show 2002



That Mercruiser is a chevy 305 V8.

------------------


Build thread for my 88 + 3800NA swap

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Ventura
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Report this Post03-01-2014 06:27 PM Click Here to See the Profile for VenturaSend a Private Message to VenturaEdit/Delete MessageReply w/QuoteDirect Link to This Post
The 3.0 liter mercruiser is just a 2.5 with a bigger displacement. It was strictly an industrial engine, such as forlklifts, marine applications, etc. and filled a need in the market when the 2.5 was discontinued. It was never used in an automotive application as far as I know. In my opinion, the 3.0 never ran as smooth or held up as well as the old 2.5. The original Chevrolet iron duke was one sweet engine. I believe GM stopped production of the Chevy iron duke in the late 70's.
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cmechmann
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Report this Post03-01-2014 08:11 PM Click Here to See the Profile for cmechmannClick Here to Email cmechmannSend a Private Message to cmechmannEdit/Delete MessageReply w/QuoteDirect Link to This Post
Are not the Marine 3.0 Gm engines reverse rotation?
I know that the 4.3 and 350 marine come in reverse rotation and standard, depending on out drive.
The old exhaust manifold/heat exchangers were heavier than the heads.
MFG had a marine version of the 3.8. Many took the water manifolds off and added a radiator/electric fan to greatly reduce weight.
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Ventura
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Report this Post03-01-2014 08:32 PM Click Here to See the Profile for VenturaSend a Private Message to VenturaEdit/Delete MessageReply w/QuoteDirect Link to This Post
Mercruiser marine had a strange way of determining the direction of rotation. In the automotive world, a standard right hand rotation engine, when viewed from the front, became a left hand rotation marine engine because the rotation was viewed from the flywheel. Confusing sometimes.

Yes, marine engines could be right or left hand rotation. I never saw a reverse rotation 3.0 but that doesn't mean they don't exist.

Mercruiser assembled Corvette engines for a brief time.

Mercruiser designed and built their own 4 cylinder 3.7 liter marine engine with 4 barrel carb which was rated at 190hp. It was half of a 460 ford V8 on an aluminum block and cast iron V8 head. It was unique to say the least.
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solotwo
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Report this Post03-07-2014 10:52 PM Click Here to See the Profile for solotwoSend a Private Message to solotwoEdit/Delete MessageReply w/QuoteDirect Link to This Post
Interesting information
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fierofool
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Report this Post03-07-2014 11:30 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
Some marine engines were reverse rotation when used in a dual engine application. Boats tend to torque to one side due to prop rotation. Rather than adding gearboxes, thus extra weight and space requirements, they made one engine to rotate in the opposite direction.

Some marine engines can be transferred to automotive applications and visa-verse. I used a 4.3 truck engine as a replacement for my 4.3 V6 Yamaha trimmed engine. Just had to change out the camshaft and everything else transferred from the old engine.
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Carcenomy
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Report this Post03-08-2014 02:18 AM Click Here to See the Profile for CarcenomyClick Here to visit Carcenomy's HomePageSend a Private Message to CarcenomyEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm sure I read somewhere that the Mercruiser crankshaft could be modified to fit the Iron Duke.
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wftb
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Report this Post03-08-2014 08:30 PM Click Here to See the Profile for wftbClick Here to Email wftbSend a Private Message to wftbEdit/Delete MessageReply w/QuoteDirect Link to This Post
The mercruiser crank and block have more main bearings than the fiero duke if I remember correctly .Thats why they are better for making power , the crank doesn't flex like the fiero 2.5 .Whats so bad about using an Archie adapter ? The purpose is to get a stronger block and crankshaft , forget about using any fiero duke parts .
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KurtAKX
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Report this Post03-10-2014 07:11 AM Click Here to See the Profile for KurtAKXSend a Private Message to KurtAKXEdit/Delete MessageReply w/QuoteDirect Link to This Post
There is an unbelievable amount of mis-information in here.

Statements about the marine engine having a different number of main bearings, Mercruiser 2.5/3.0 being reverse rotation, S10 engines being directly swappable, etc.
I don't have the energy to debunk every one but here the short list:

Same number and same size main bearings between auto and marine 2.5/3.0
Different size rod bearings between the auto and marine 2.5/3.0 due to different connecting rods- marine rod journals are wider.
2.5/3.0 marine are standard rotation.
S10 engines don't have the hole in the side of the block up front to mount the Fiero water pump.
I REALLY WISH PEOPLE WOULD STOP SAYING S10 ENGINES ARE A STRONGER BOLT-IN ALTERNATIVE. THEY ARE NOT.

Ventura is correct in everything he said. I used different studs than he's suggesting, but I did convert my 2.5 to adjustable valvetrain several years ago using GM 250 I-6 rocker arms.
(I used ARP Vortec 305/350 studs- Vortec heads are metric on the bottom thread into the head, and then standard 3/8" fine thread on the upper thread where the rocker nut goes)

[This message has been edited by KurtAKX (edited 03-10-2014).]

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TopNotch
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Report this Post03-10-2014 10:02 PM Click Here to See the Profile for TopNotchClick Here to visit TopNotch's HomePageSend a Private Message to TopNotchEdit/Delete MessageReply w/QuoteDirect Link to This Post
Correction to an above post. The term "Iron Duke" was introduced in 1977, with the introduction of the original version of the Pontiac 2.5 (not Chevy or Mercruiser).

Because of problems with the Chevy aluminum 2.3, they emphasized that it was made of iron.
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Ventura
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Report this Post03-10-2014 10:41 PM Click Here to See the Profile for VenturaSend a Private Message to VenturaEdit/Delete MessageReply w/QuoteDirect Link to This Post
The Pontiac 2.5 and the Pontiac 301 V8 connecting rods are the same. Pontiac made a turbo 301. I've wondered if the turbo rods are forged instead of cast.
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wftb
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Report this Post03-10-2014 11:34 PM Click Here to See the Profile for wftbClick Here to Email wftbSend a Private Message to wftbEdit/Delete MessageReply w/QuoteDirect Link to This Post
The funny thing is the mercruiser engine is based on the 153 CI 4 cylinder that debuted in 1962 with the intro of the chevy II .It was a four cyl version of the chevrolet 230 CI 6 cylinder motor .This engine got the nickname iron duke from the automotive press in general because of its reliability .It was really bullet proof .But GM never called it the Iron Duke .Pontiac simply took advantage of the old motor's reputation and called the new motor that was designed for the X cars the Iron Duke even though it was nothing of the sort .Once the X car version of the duke was introduced , the chevy motor was only sold for industrial and marine use .Which should tell you something about the new motors reliability .I dont think GM would have continued to make the old motor if the new motor could cut it for marine use .There is no way a fiero duke could be run at 4500 rpm all day long like boaters do with their mercruiser dukes .The 3 litre version of this motor was never used for cars , as stated earlier .
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Carcenomy
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Report this Post03-12-2014 01:29 AM Click Here to See the Profile for CarcenomyClick Here to visit Carcenomy's HomePageSend a Private Message to CarcenomyEdit/Delete MessageReply w/QuoteDirect Link to This Post
I recall reading about a gentleman who's done a few Mercruiser cranks to the Pontiac Duke, to my understanding you needed alternate rods and pistons, plus machining to the crank for the rear main seal and flywheel bolt pattern.

And that it's a terrible idea as the Duke block itself isn't beefy enough.

If I find the thread I'll post it up, but in all fairness by the time you spring for the marine crank, the machine work, the custom pistons, custom rods, headwork to support it... you're quite a few dollars into a Duke. It doesn't seem economical at all.
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jscott1
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Report this Post03-12-2014 03:50 AM Click Here to See the Profile for jscott1Send a Private Message to jscott1Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by TopNotch:

Correction to an above post. The term "Iron Duke" was introduced in 1977, with the introduction of the original version of the Pontiac 2.5 (not Chevy or Mercruiser).
...
Because of problems with the Chevy aluminum 2.3, they emphasized that it was made of iron.


Kind of bizarre bragging about the fact that the engine is cast iron...like that's a good thing, lol
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Csjag
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Report this Post03-12-2014 05:09 AM Click Here to See the Profile for CsjagClick Here to Email CsjagSend a Private Message to CsjagEdit/Delete MessageReply w/QuoteDirect Link to This Post
Like GM had a habit of doing, they redesigned the Vega engine for the last model year and greatly improved it by installing cast iron cylinder sleeves. That made it a good motor but it was too late.
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wftb
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Report this Post03-12-2014 08:13 AM Click Here to See the Profile for wftbClick Here to Email wftbSend a Private Message to wftbEdit/Delete MessageReply w/QuoteDirect Link to This Post
The Vega engine was a strange one .Who puts a cast iron head on top of an aluminum block ? And then uses an unproven etching process to avoid using liners? All in all a bad design . The etching process in conjunction with other advancements is in use by Mercedes and some Porsche engines now with good success though .
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Report this Post03-12-2014 10:36 AM Click Here to See the Profile for KurtAKXSend a Private Message to KurtAKXEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by wftb:

The Vega engine was a strange one .Who puts a cast iron head on top of an aluminum block ?


Cadillac.
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fieroguru
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Report this Post03-12-2014 04:55 PM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Carcenomy:

I recall reading about a gentleman who's done a few Mercruiser cranks to the Pontiac Duke, to my understanding you needed alternate rods and pistons, plus machining to the crank for the rear main seal and flywheel bolt pattern.


If I find the thread I'll post it up.


You might be thinking about this thread:
http://www.fiero.nl/forum/A...120111-2-093668.html
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DanDamage
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Report this Post03-12-2014 05:28 PM Click Here to See the Profile for DanDamageClick Here to Email DanDamageSend a Private Message to DanDamageEdit/Delete MessageReply w/QuoteDirect Link to This Post
all i know is i used a Mercury computer to fix all my senosors on my 84
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Carcenomy
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Report this Post03-13-2014 02:44 AM Click Here to See the Profile for CarcenomyClick Here to visit Carcenomy's HomePageSend a Private Message to CarcenomyEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fieroguru:


You might be thinking about this thread:
http://www.fiero.nl/forum/A...120111-2-093668.html


This one
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DanDamage
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Report this Post03-13-2014 11:49 AM Click Here to See the Profile for DanDamageClick Here to Email DanDamageSend a Private Message to DanDamageEdit/Delete MessageReply w/QuoteDirect Link to This Post
once i got my 84 to stop throwing a code and had it idling perfect it was smooth sailing till the TBI needed to be rebuilt a few years later
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Report this Post08-09-2014 01:36 AM Click Here to See the Profile for concorde01Click Here to Email concorde01Send a Private Message to concorde01Edit/Delete MessageReply w/QuoteDirect Link to This Post
ok i have to bring i up. even if the tread is old. i want to use a mercruiser 3.7 4cyl in my 84 fiero 2m4. how would i get or desing a adapter to make it work with my 4spd?
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Report this Post08-09-2014 07:56 AM Click Here to See the Profile for TopNotchClick Here to visit TopNotch's HomePageSend a Private Message to TopNotchEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by concorde01:

ok i have to bring i up. even if the tread is old. i want to use a mercruiser 3.7 4cyl in my 84 fiero 2m4. how would i get or desing a adapter to make it work with my 4spd?


V8 Archie?

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