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do i have a 260 hp 350 or a 350 mag how do you tel the difference?

T

tdpb2008

New member
do i have a 260 hp 350 or a 350 mag how do you tell the difference?
i have a 85 checkmate enforcer 24' not sure if it has a 350 mag or just the 260 it came with an aftermarket flame arestor so i cant see if it says 260 or 350 mag

also wondering if it would be a 2 bolt main or 4?

id like to get the boat to run neer 70mph...what mods would i be looking at to get neer my goal? its all stock other than a flamearrestor

thanks for any help
 
I believe it would be a 2 bolt main 260hp. I dont think the mags came out till the late 90's. There should be a serial plate on your valve cover that will identify what it is through your merc dealer.
 
There has been alot of confusion on this subject. I am not sure what the truth is, but my brother has a 1986 or 87 that says on the valve cover label that it is a 350mag 280hp. I thought all along that 350 mag's were 300hp.
 
so i cant put much power to it then if its a 2 bolt main?
how much power can you put to a 2 bolt main?

what can i do to make my boat run around 70 mph...thats what id like to shoot for
 
The newer Mags are port fuel injected and approx. 300 horse. The early mags with the 4bbl carb were called 260 horse. Merc has had many different horsepower ratings for the 350 over the years.
The only way to tell for sure is to get the engine serial number and get with your dealer like was posted above.
 
If you can give me the serial #'s off your block I can tell you what it is. Should be located top where the bell housing is, I drawing a blank right now which side it's on.
 
If your looking for the casting # is on your right,that will tell you the engine size,probably won't tell you 2 or 4 bolt main because most 350's could be either,the block would get machined and drilled for the 4 bolt caps.If you have a Mercruiser seriel # (should be on the valve cover) will tell you the engine and hp.
 
The main reason for 4 bolts is the "shock" during shifting gears. On a boat, you have no shock. The enforcer is a somewhat heavy hull so you will need a little bit of power to push it. I think the 330hp BBC would push it near 70 but your SBC does not have the torque of the big block. I would think that 350hp SBC should get you what you need????
 
lcboater said:
If your looking for the casting # is on your right,that will tell you the engine size,probably won't tell you 2 or 4 bolt main because most 350's could be either,the block would get machined and drilled for the 4 bolt caps.If you have a Mercruiser seriel # (should be on the valve cover) will tell you the engine and hp.
Click to expand...

GM's serial numbers tell you if it's a 2-bolt or 4, and it could be either. In 1980 to 1985 and we are talking about a 1985.
If the casting numbers are 14010207 or 14010209 it's a four bolt. If it's a different number for that year more than likely a 2-bolt. Or a siamese 350 82 to 86 ( which I doubt) with a # 366286 it's a four bolt.
Mercruiser did not modify blocks in production engines they used what they were supplied with from GM.

I have a 78 350 finished on a stand and it was rated at 280 hp stock and it's a 2- bolt,has a mild cam and 9:1 compression and with headers will make 300+HP.
You can build up a 2- bolt and it will last. I would not go with high compression or past 350 hp.

Oh and is that looking at it from the front or the back?
 
many years ago i remember reading an article in "boating" magazine about the sea ray pachanga. it was (supposidly) the first boat to run mercury's new 350 mag. it was rated at 270hp and featured a different intake manifold and different exhaust giving the extra 10hp over the standard 260.

that was 1986, came out the same time as the new alpha drive, and i believe that was also around the same time that they came up with the bright idea of bolting a 454 to an alpha drive.

fuel injected mags didn't come along until the mid 90's and they delivered a solid 300hp

to find out for sure, get the engine serial number and run it, that will tell you what you have, my bet is a standard 260.
 
my boat is in storage right now but ill have it out in another month or so when the weather gets better...

i do remember seeing a tag on the valve cover saying 260/270 hp now that i think of it...but i dont know if that means its a mag or even if it means it would be a 4 bolt main...im just hopeing its a 4 bolt main!
 
my boat is in storage right now but hopeing i will be getting it out in a month or so when the weather gets nicer...

i do rember it saying on a tag 260/270 hp on one of the valve cover bolts...i just hope its a 4 bolt main!
 
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