Marine V8 swap?
05-31-2010, 01:53 PM
#1
Intermediate
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Marine V8 swap?
Just throwing this out there. I have a boat with a blown outdrive. The motor is in great shape, however it's an old carbuerated SBC (I'm assuming iron block and heads). Would it be worthwhile to salvage the motor for a future V8 swap if the 2.5 n/a (1984) ever suffers major catastrophe? Or just sell the motor/part out boat, or sell boat as is? No plans on V8 conversion, just would hate to get rid of a good motor if it could come in handy in the future.
05-31-2010, 02:22 PM
#2
Three Wheelin'
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Generally speaking the marine engines are not a good choice if it a marine specifice engine. Aside from the limited RPM range, often time bolt bosses are not in the same place or sometimes there at all. If you are hell bent on a SBC conversion i am quite sure you could trade your old boat for a good 350 or use the proceeds off selling it to buy a LT1.
05-31-2010, 03:15 PM
#3
Nordschleife Master
Not worth the effort... and old carbed SBC based marine motor is 240 HP at best... horrible power to weight ratio for a car... but because it is based on a truck motor is great for a boat in that it is set up for a broad power band (to 4000 rpm or so...)
you would be better off selling the boat as is (try joining Iboats.com) or finding a used outdrive and selling it, then using the proceeds of the sale to fund a new engine for the Porsche if you want...
what type of drive is in the boat now?
you would be better off selling the boat as is (try joining Iboats.com) or finding a used outdrive and selling it, then using the proceeds of the sale to fund a new engine for the Porsche if you want...
what type of drive is in the boat now?
Last edited by JohnKoaWood; 05-31-2010 at 08:18 PM.
05-31-2010, 08:09 PM
#4
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this would not be a good choice, but there are quite a few guys here with extensive knowledge to help you when you get a better engine... you should maybe sell this motor.
05-31-2010, 08:19 PM
#5
Nordschleife Master
05-31-2010, 08:29 PM
#6
Rennlist Member
The boat motor is cammed wrong for auto application.
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05-31-2010, 08:38 PM
#8
Rennlist Member
You could be right if WOT tuning is desirable.
05-31-2010, 09:15 PM
#9
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Alot depends on what the motor in the boat is. 25 years ago I worked in th summers with a boat mechanic. We did mostly rebuilds of sbc's and commonly used camaro or corvette motors as a base for the rebuilding efforts. These were typically either go-fast boats or cabin cruisers with go-fast owners.
An old 327 or 350 with 4 bolt main made a great boat motor!
An old 327 or 350 with 4 bolt main made a great boat motor!
06-01-2010, 11:59 AM
#13
Race Car
Interestingly, I researched a project to install 2 928S4 motors into a 28ft Cigarette. The boat had its original 1972 LT1 Corvette motors. The two motors were worth more than the boat by far. I wound up talking to Devek IIRC who had already developed 928 manifolds and adapters for marine use. devek told me not to waste my time as they had already outfitted a scarab with the 928 motors. He had the marine manifold(stainless) on the shelf and he would sell them at cost(>$1000). the SBC iron block was much lighter and more powerful. A marine motor is usually very strong, boats and airplanes operate at 90% load all the time. A car motor works at ~10% most of the time. A SBC marine motor can be a good choice for automotive use if it's cammed right.
06-01-2010, 12:07 PM
#14
Drifting
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I've always wondered about modern (Mercruiser/Volvo) boat engines. They all use GM iron blocks, but I wonder how much development takes place. Modern boat engines use fuel injections (not carbs), and electronic ignition. Yes, they operate at higher constant loads, but I wonder how much the internals vary from the old street motors they are based on. They still just quote horsepower, and a solid small block (5.7L) boat engine will 300 horsepower (and run 800 hours at that load).
I think the weight of the iron block seals the deal.
I think the weight of the iron block seals the deal.
06-01-2010, 12:30 PM
#15
Nordschleife Master
I've always wondered about modern (Mercruiser/Volvo) boat engines. They all use GM iron blocks, but I wonder how much development takes place. Modern boat engines use fuel injections (not carbs), and electronic ignition. Yes, they operate at higher constant loads, but I wonder how much the internals vary from the old street motors they are based on. They still just quote horsepower, and a solid small block (5.7L) boat engine will 300 horsepower (and run 800 hours at that load).
I think the weight of the iron block seals the deal.
I think the weight of the iron block seals the deal.
major difference is the cams (exhaust duration, lift and timing have to be controlled to eliminate the chance of sucking water back into the motor) as the exhaust manifolds have water injected much the same way older cars used air injection for emmisions, but marine motors use it to cool the exhaust..
the Marine use cams are very closely related to truck cams... some folks are even running transplanted Van motors in their boats...
a street automotive motor is NOT acceptable for use in a boat, and vis a versa.. boat motors are NOT acceptable for use in a street car, they are tippicaly rated at 4500 RPM or below, constant duty, and emiisions are out the window on a marine use motor...
for perspective, next time you are driving... stay under 4500 RPM for an entire trip... now they WILL give steady state running WOT... but quickly fall out of their opptimal power band if over reved, and will destroy internals if over reved!
A marine motor is a POOR POOR choice for a street car....