50 horse merc to a 75 horse merc.

[Fish to Win]

I'm working w/ a guy im Maple Grove who does motor work and I was wondering if a 1991 75 horse is going to add enough speed and take off power than my current 1983 50 horse merc. to make enough differance. I have a 18 foot blufin and the 50 horse is way under powered.

Thanks- I believe he will do the swap for around $600- $800. but again is gaining 25 horses going to make that much of a differance.

Thanks-

[Ralph Wiggum]

What HP is your boat rated for? It will make some difference, I am sure, but if you're still underpowered with a 75, it's not worth it in my opinion.

[Fish to Win]

I believe it is rated for a 125 horse motor

[Ralph Wiggum]

Yikes. I wouldn't bother with the switch.

[marine_man]

Using the 75% of max rpm rule of thumb, you'd still be underpowered with the 75hp motor. So, will it help? Probably. Will it still be underpowered? Definitely.

marine_man

[Fish to Win]

I just spoke to the boat guy that I'm dealing w/ and he said the 1991 75 horse merc. is the same as a 90 horse merc. They just label some diff't??? Is this true??- He also added that his 1991 75 merc. is valued at $2100 and mine has a $500 trade in value. Are his numbers close?

Thanks guys-

[sparcebag]

I was just not long ago pricing Mercs to bid on a 1985 50 HP 4 cyl. the going prices were around 1000.00 avg. high being 12-1300 lows 900+.That 91 75 HP is about right but the qoute on yours seems low,But as a tradein it may be righton?

[chub]

With the bigger gear case and larger prop of the 75, you'll notice a difference. Whether it's worth the money to upgrade is mostly in the eye of the beholder. I believe the 75/90 difference is done through carburetion. Same block and gear case, atleast on 1993 and newer 2stroke Mercs. Not 100% sure on 1991 models?

[marine_man]

That's correct regarding the carbs being the main difference between a 75 and 90.

marine_man

[SkunkedAgain]

Don't believe everyone about being "underpowered." That's salesmen talk for needing to have the max horsepower on a boat. Personally I don't believe in that.

You've probably been relatively happy with your 50 horse for a few years and are thinking that a little bump in power would give you more speed. In my opinion that's worth the money unless you feel like your boat is a complete dog right now. Granted a 50hp sounds small for an 18 footer, but if you've been happy then that's all that matters.

Don't buy into the hype that you need a big motor. 50hp is perfect for some people and unbelievably slow for others. Figure out what type of boater you are, what kind of strain you put on your vessel, and go with your gut feeling.

[King Canada]

That 50 horse is probably worth close to what the 75 is worth or should I say "as marketable". You'll probably get around 30 mph out of the 75 horse. They sold alot of underpowered Bluefins back in the 80s. If you are confident in the 75 horse go for it.

[hydro]

Either way you will still be underpowered from a performance standpoint.

But.....The 75 will put out about 75HP and not 90HP even if it has the same block. The carburetion makes that difference. You will notice a jump in planing and top end performance, largely due to the prop size mentioned above. On the down side, the 75 will not idle nearly as good as that old 4 cylinder 50, and you will see that your minimum trolling speed will increase quite a bit, again because of the prop size.

Why not shop around for something in the 90 hp range. The upside/downside will be the same and you will have more power to get the boat out of the water.

[boatfixer]

Skunked makes a good point. One guys fast is another guys slow. I will say though that overall hull design is going to impact performance. With that boat, I think you would need get much closer to the max rating to really see an large, justifiable increase in performance. I don't what you are running for speed now, but to give you an example, I've got a customer that has an 18ft Bluefin with an 85 on it and it runs 33-35 mph. Its a Force, but even a 90 merc, I'm guessing 35-38 or so. IMO, not enough to justify the money.

[rodmaker]

I had a 75 Merc on my Alumacraft 1895 Compeditor (tiller) it went 33 - 37mph. Worked good for me, no complaints. I had that boat/motor for 14 years.

[boatfixer]

Thats some of the hull design difference I was talking about.

[rodmaker]

At the time I was thinking about going with the 90 Merc. But they told me there was only 2-4 mph faster. Couldn't justify spending the extra $ for that.

[dan z]

we went from using a 40hp to a 75hp on a mr pike 17ft and OMG hang on it made a world of difference I know your blufin will be much happier with the 75 and so will the gas tank. once on plane with the bigger motor you can back down and cruise were as the smaller motor was always screaming in th 5000 rpm area I can run about 35-37 when on plane depends on load. hope you get what your looking for DZ