Easy Swap?? 3.7 merc to replace 4.3 merc?

S

stangdawg

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Jun 10, 2010
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Hi All,

I have my eye on a nice condition 1988 19 foot Cobalt with a milky 4.3 merc, the price is right at a grand, but the motor is basically shot with its milky oil condition, rebuilts are priced out too high and doesn't seem easy to find a used 4.3

I've seen a few local merc 3.7s for sale, the orignal 4.3 has a 175 hp rating and the 3.7s seem to have the same hp range, but my curiousity is if its a simple pull and swap for the two engines

the 3.7s I am seeing forsale too are fresh water cooled systems too, so that's a bonus as well, as I'd like to use the boat in salt water

what am I getting myself into, what are the problems I could face?

thanks
 
fishinpa

fishinpa

Petty Officer 1st Class
Joined
Nov 2, 2009
Messages
221
Re: Easy Swap?? 3.7 merc to replace 4.3 merc?

Just an "opinion " but get your eye on another boat or find a 4.3 to replace whats in there if it is in fact a bad engine...





fish
 
S

stangdawg

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Re: Easy Swap?? 3.7 merc to replace 4.3 merc?

the lower units would be the same right? perhaps differnt mounts

anyone? I can't see why it'd be that hard
 
Bondo

Bondo

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Messages
71,353
Re: Easy Swap?? 3.7 merc to replace 4.3 merc?

anyone? I can't see why it'd be that hard
Click to expand...

Ayuh,... The Problem is, you're wanting to install the WORST motor ever sold by Mercruiser....
And,..
It's been out of production for nearly 20 years,... Many parts at NLA...

Do a search on this forum for "470"... You'll see what I mean...

4.3ls are a dime a dozen,+ reasonably Cheap....
 
180shabah

180shabah

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Mar 26, 2005
Messages
4,995
Re: Easy Swap?? 3.7 merc to replace 4.3 merc?

$1000 for a 2 decade old boat with a bad engine, sounds a little high to me.....

The 4.3 has been in millions of s-10, astros etc since the mid 80's, surely you can find one in rebuildable condition - just keep it simple and match the vintage of the one you are replacing.
 
S

stangdawg

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Jun 10, 2010
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Re: Easy Swap?? 3.7 merc to replace 4.3 merc?

OK, so swapping for a 3.7 wasn't a good idea,

but to use a same vintage 4.3 from a car, isn't the motor different, and how would you prep a automotive 4.3 to work in a marine application?

I have not worry about my ability to swap motors, but I always though that you can't mix automotive and marine

if you could elaborate on using an automotive 4.3, that'd be a huge help

thanks

Jim
 
Eric 3.7LX Alpha 1

Eric 3.7LX Alpha 1

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Joined
Mar 27, 2010
Messages
3,028
Re: Easy Swap?? 3.7 merc to replace 4.3 merc?

All accessories that have ability to make spark must be marine: alternator, distributor, carb, starter, etc. must be marine

All accessores in salt water( unless closed cooling): water pump, brass freeze plugs, thermostat,etc, must be marine.
 
180shabah

180shabah

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Mar 26, 2005
Messages
4,995
Re: Easy Swap?? 3.7 merc to replace 4.3 merc?

Differences from auto to marine:

Core plugs, head gasket, cam, waterpump, ALL ignition, fuel, and electrical components.
 
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