Best Mercury Outboard Ever Made - 1984 50hp 4cyl

[CaptainDinghy]

jimmbo - thanks for the information above, very good to know. I knew there was a different HP rating scale that occurred in the 80's but didn't know exactly what changed. Interesting that the older 85hp is the same as the newer 75hp.

Would you say the best upgrade as far as power to weight ratio would be going to a 75hp 4cyl or a 90hp 6cyl. Would that extra 15hp offset the extra 100lbs engine weight and still feel improvements on performance?

Generally, do the lower HP 6cyl consume noticeably more fuel than the higher HP 4cyl? All I have right now is a single 6gal pre-mix tank under the splash-well, however I have been contemplating doing some rearranging to get a second tank back there (which of course again means more weight...).

 

[jimmbo]

jimmbo - thanks for the information above, very good to know. I knew there was a different HP rating scale that occurred in the 80's but didn't know exactly what changed. Interesting that the older 85hp is the same as the newer 75hp.

Would you say the best upgrade as far as power to weight ratio would be going to a 75hp 4cyl or a 90hp 6cyl. Would that extra 15hp offset the extra 100lbs engine weight and still feel improvements on performance?

Generally, do the lower HP 6cyl consume noticeably more fuel than the higher HP 4cyl? All I have right now is a single 6gal pre-mix tank under the splash-well, however I have been contemplating doing some rearranging to get a second tank back there (which of course again means more weight...).

I'm not going to say they are the exact same engine, I don't know if the newer 75 has the power ported pistons the 85 had. There might also be some differences in the reed valving

I don't think there is a 100lb difference between the 4 cylinder and the six, unless the 4 was manual tilt and the 6 had power trim, but even then I don't think it is that much.

The six will burn a bit more at idle, at higher speeds the difference may reverse, hp does determine fuel usage, but the six is much easier to utilize exhaust tuning over a larger rpm range than a four is. Exhaust tuning can improve fuel economy dramatically as well as increase power

Myself, I am very partial to the inline sixes. had two of them

 

[CaptainDinghy]

Very good info. I think I'll just need to keep an eye out for some more HP. Was the mounting configuration (bolt pattern) the same on your two above? Just this week I completed my transom rebuild and it would certainly be nice if (when I repower) I could use the same bolt holes and tilt/trim setup.

 

[jimmbo]

No the blue one was a 78, and used the old pattern, The brown one was an 84, the first year with the OMC bolt pattern. The old engine had the original external trim system and the newer one had the integral. The new engine was also mounted an inch higher on the transom. You can make the pics bigger by clicking on them

 

[CaptainDinghy]

No the blue one was a 78, and used the old pattern, The brown one was an 84, the first year with the OMC bolt pattern. The old engine had the original external trim system and the newer one had the integral. The new engine was also mounted an inch higher on the transom. You can make the pics bigger by clicking on them

Hmm. Interesting. I believe my motor is an '84, but it's got the external trim like your older blue one. I guess I'll need to look for an early 80's model then to match it...

 

[jimmbo]

83 was the last year for blue on the cowl, 84 and 85 were brown like my 115. last year for the external trim was 83 on the 6s and on the 80hp. the smaller engines used the external trim a couple more yrs