I've been reading up on motors two replace the iron duke, i don't wanna go v6 and i don't want to go v8 i would really like to do a turbo 4. I KNOW not to turbo the duke because the bottom end cant handle much power at all. so i read the the marine 2.5 mercruiser motor is the same bloke as the duke but has a lot stronger crank and internals to handle the constant open throttle rpms of the boat prop (around 4000rpm is what i've heard) has anyone else heard anything about this or has any info they would like to share with me? Thanks!
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11:50 AM
PFF
System Bot
Gall757 Member
Posts: 10938 From: Holland, MI Registered: Jun 2010
Although the Iron Duke ended up in boats, the majority of the 2.5 liter Mercruiser setups were actually a Chevrolet 4 banger and have nothing in common with the Pontiac Engine, so check it out carefully.
(Paul?) Duff built one years ago. The last time I saw the car was at a FOCOA meet at the Lake of the Ozarks in Missouri maybe 2001. The Fiero had a marine theme. I probably have photos somewhere, but don't have a clue where at this time.
this question has been asked in the past. figuring the Marine engine is better built... what you must know is it's not a "super duty" automotive engine.
Marine based engines are not designed for automotive use.
the cam shaft and cylinder head are meant for ONLY marine use.
the block doesn't share much in common with automotive engines either except the bare engine case itself being the same shape on the outside. everything else is specific to marine based applications.
if you want a good upgrade and remain 4 cylinder - go with a 2.3L HO DOHC Quad 4 engine from a Beretta. while they are hard to find, they have 180hp horsepower stock (more than a 2.8, 3.1, 3.4, 3100, and about the same as a 3400 SFI)
they are lighter engines than the 2.5L duke, and have twice the horse power.
just food for thought...
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02:09 PM
ericjon262 Member
Posts: 3131 From: everywhere. Registered: Jan 2010
this question has been asked in the past. figuring the Marine engine is better built... what you must know is it's not a "super duty" automotive engine.
Marine based engines are not designed for automotive use.
the cam shaft and cylinder head are meant for ONLY marine use.
the block doesn't share much in common with automotive engines either except the bare engine case itself being the same shape on the outside. everything else is specific to marine based applications.
if you want a good upgrade and remain 4 cylinder - go with a 2.3L HO DOHC Quad 4 engine from a Beretta. while they are hard to find, they have 180hp horsepower stock (more than a 2.8, 3.1, 3.4, 3100, and about the same as a 3400 SFI)
they are lighter engines than the 2.5L duke, and have twice the horse power.
just food for thought...
the quad 4 won't have the low end grunt of the V6 engines, but if I was going to do a 4 cyl fiero, it would probably be a quad.
------------------ there's a Group on 60degreeV6.com for us 660 Fiero owners!
this question has been asked in the past. figuring the Marine engine is better built... what you must know is it's not a "super duty" automotive engine.
Marine based engines are not designed for automotive use.
the cam shaft and cylinder head are meant for ONLY marine use.
the block doesn't share much in common with automotive engines either except the bare engine case itself being the same shape on the outside. everything else is specific to marine based applications.
if you want a good upgrade and remain 4 cylinder - go with a 2.3L HO DOHC Quad 4 engine from a Beretta. while they are hard to find, they have 180hp horsepower stock (more than a 2.8, 3.1, 3.4, 3100, and about the same as a 3400 SFI)
they are lighter engines than the 2.5L duke, and have twice the horse power.
just food for thought...
would the quad four bolt to the stock 88 5speed tranny?
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08:21 PM
mferrell Member
Posts: 243 From: Elkveiw, Wv, USA Registered: Feb 2012
Some more info for you: the earlier 2.5 Mercruisers are the true Chevy iron dukes. the later 2.5 Mercruisers are the Pontiac 2.5's like our Fiero's. Like said above tho the block is the only thing that is the same. boat motors have a totally different "tune" they are designed to sit and run at one rpm not accelerate, decelerate constantly. the intake and exhaust manifolds are very big and bulky cast iron water cooled manifolds. there is no spark advance on the distributor. the Chevy motor has a different bolt pattern than the Pontiac, also . Oh by the way the Chevy motor has a few more Hp than ours do. My boats are 120 hp but that's with an unrestricted exhaust.
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08:24 PM
lou_dias Member
Posts: 5356 From: Warwick, RI Registered: Jun 2000
the iron duke in the fiero has nothing to do with the original iron duke other than name .when gm decided to build the X cars , they totally redesigned the duke to make it cheaper and lighter than the old duke .production of the old motor continued for marine use as a 3.0 litre .i have never seen a 2.5 mercruiser I/O drive .you can use the 3.0 marine duke in a fiero but you need an adapter plate like you would use for a small block chevy .the marine duke has more main bearings and a stronger crank and more displacement .you can get more HP out of it .but it is not a quick and easy swap nor is it a source for high performance parts for the fiero duke .not much interchanges between the two .
The 2.5 marine engine came from the old Chevy II's. There was never a Pontiac 2.5 marine engine. When the Chevy 2.5 was discontinued by GM it was replaced by the 3.0 industrial engine (fork lift). GM had a large marine engine division but Pontiac was never associated with it.
Marine engines are the same as automotive except for cams; brass freeze plugs and water pumps.. Cams are ground for peak torque around 3000 rpm's (when the boat is trying to plane) and peak hp around 4600 rpm's.
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12:34 AM
AL87 Member
Posts: 2578 From: Bradenton, Florida, United States Registered: Mar 2010
I dont know if anone has mentioned this yet, but the mercruiser engine uses the chevy v8 bell housing bolt pattern, does it not? it would cost more for the conversion kit to do that, might as well swap in a v8 lol. or keep it simple and stick with a metric bolt pattern engine.
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01:14 AM
Nov 27th, 2012
mferrell Member
Posts: 243 From: Elkveiw, Wv, USA Registered: Feb 2012
Actually the original mercruiser 4 cylinders where the 2.5 chevy. I have 6 of them in my yard right now.(I have a lot of friends who are boaters, I store boats for the winter for a lot of them) they later went to the 3.0's and also did use the pontiac 2.5's at some point because I have one of them out here also in a late model bayliner.
quote
Originally posted by wftb:
the iron duke in the fiero has nothing to do with the original iron duke other than name .when gm decided to build the X cars , they totally redesigned the duke to make it cheaper and lighter than the old duke .production of the old motor continued for marine use as a 3.0 litre .i have never seen a 2.5 mercruiser I/O drive .you can use the 3.0 marine duke in a fiero but you need an adapter plate like you would use for a small block chevy .the marine duke has more main bearings and a stronger crank and more displacement .you can get more HP out of it .but it is not a quick and easy swap nor is it a source for high performance parts for the fiero duke .not much interchanges between the two .
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10:13 PM
KurtAKX Member
Posts: 4008 From: West Bloomfield, MI Registered: Feb 2002
Actually the original mercruiser 4 cylinders where the 2.5 chevy. I have 6 of them in my yard right now.(I have a lot of friends who are boaters, I store boats for the winter for a lot of them) they later went to the 3.0's and also did use the pontiac 2.5's at some point because I have one of them out here also in a late model bayliner.
Pics or it never happened. I'd be willing to bet that the "Pontiac 2.5 in that boat has a Chevy bellhousing pattern and a non-crossflow head, just like all the others.
already heat shrinkwrapped for the winter or I would get you a pic. I haven't paid attention to which head is on it, but it is the metric bellhousing, not the old v-8 one. a buddy of mine just bought this bayliner a couple of months ago. I didn't realize it was different till I was winterizing it for him and all the drainplugs were in the wrong places. we got to measuring and figured out the bellhousing was wrong
