serial numer

[slikcraft]

Who can help me. I have I Merc with serial number 55711971
engine number 5611651 who can tell me how much Hp this engine have and off this engine can make high rpm and the year of building.

Thanks

[mellowyellow]

try here:
http://www.marinshopen.se/guide/guide.htm

[slikcraft]

Who can Help me.

[mellowyellow]

did you add 1 digit to your serial number by mistake?
the link I provided shows 1980/81 175hp for serial #'s
5488752 - 6618750.

[Cp]

....a 3.4 Liter. Probably the Hi-Perf EFI model, but kinda hard to tell from the picture.

[slikcraft]

That is correct it is a 3.4 carburated version but how much Hp 250 ,275 or 300 and how much rpm.:mad: :confused:
The numbers are correct I have check it out.

[Cp]

From memory, so Raceman will have to check my math, but I think the production motors were all carbed, in 275 and 300 versions that maxed at about 6200 or so. The Hi-Perf model I remember was an EFI rated at 325/6800, if memory serves. There may have been a carbed Hi-Perf, too. Norris? Gearcase is the weakest link.

Cp

[87vantage]

Do you have to get the serial #s off of the merc and then call a dealer to figure out what you have? I am looking at a pair today and just curious on how to Id them? They are suppose to be 92 model carb motors,with one being a counter rotating model! Thanks S&F

[Raceman]

If the cowl stickers are original it's a high perf 3.4 from Merc High Performance. I've never seen one in a carb version, but guess it's possible. They differed from the production 300 because of plastic reeds and tighter heads, and may have had solid mounts also, but I'm not sure of that.

Regardless of what version they are, they're torqy motors and don't require RPM to push a boat fast and won't live if you try to turn em hard. I like to keep mine in the 5's. CP's correct that the gearcases are a problem, not only because of some design deficiencies in the early models, but also because the parts are long ago NLA and trying to access many of them superceeds to a complete gearcase assy which costs many times what the motor is worth IF they're even still available. In any case, if you try to run em in offshore conditions where the powerheads load and unload at full throttle you'll break powerheads AND gearcases.

They're good old motors when used right, but I"ve always described em as workhorses more than racehorses.

I don't know that I've ever seen a horsepower rating on the high perf versions but would guess CP's figures would be close. I just wouldn't recommend turning the engine 6800.

Incidentally, if it's a high perf powerhead it would have left the factory with no paint on it. The std 300's I've got are black, and I think the later ones with the Cosworth cast block were black also in the production version, but don't know for sure.