Motor size question

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Rib

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I've been reading here for a while, but this is my first post, great forum.

I have a 1972 Richline "Guide" 16' fishing boat. It's got a 1976 Merc 200 20HP outboard that I've been fighting for a couple of years and I'm just plain tired of it. I added a front deck, seats, and a bow mount trolling motor up front, the rest is pretty much stock, so not a lot of added weight. The old motor has an old set of "whale tails" and I always thought the performance was satisfactory with them, years ago I tried taking them off, but the boat would not get up on plain without them. I've always felt the boat was plenty fast enough with the old Merc 200.

Per the plate on the boat, it's rated to 40 HP. I'm thinking about buying a brand spanking new Mercury 4 stroke (tiller steer/manual start) motor. I just want the peace of mind of brand new...I'm tired of tinkering and worrying. I keep hesitating because I really prefer the lighter weight and portability of a 20 HP motor but I'm scared to death of buying it and finding it won't bring my boat up on plane. Going up to a 25 or 30 adds about 50 pounds that I don't want to add and, of course, quite a bit more money.

Anybody have a feel for whether a new 20 HP motor would be able to bring this size boat up on plane without adding a whale tail? I understand the HP measurement ratings changed over the years. The new motors look to have a 3 blade prop vs. the 2 blade prop on my old motor. Would a 20 HP be a HUGE mistake?
 
I guess that I'd go as big as I could afford. You're not going to be taking a 4 stroke 20 hp on and off with any regularity. And even with the added 50 lbs going up in size to a 30 would be a significant performance improvement. If you're already hesitant about the 20, then I wouldn't go for it. I doubt your performance would be any worse than your current 2 stroke 20, but why take the chance?

Good luck!
 
I used to have an old Merc 200. You are right. No matter how much I fooled with it, and no matter how many new parts I put on it, it was still finicky. I hated it, and put WAY too much money into it. I couldn't get rid of it fast enough.

If your boat is rated for 40, I wouldn't go less than 30hp. Bolt the motor onto the transom. Not only will a 30 or 40 get on plane with more authority, it will also likely use a little less fuel than a 20 that would have to work really hard.

Every time either I or any of our customers have "cheaped out" and got a smaller motor for their boat than it was rated for, every time (100%) they came back in a year or two wanting to go to max rated HP per the boat. Mine's rated for 40 hp, and my 25 does well. But if it weren't for the fact that the motor was basically free, I'd have already sold or traded it for a 40. And also in my area, 25hp motors are generally worth about the same as-and in a lot of cases MORE, than a 40, because almost every public duck hunting area is 25hp max.
 
Personally if it's rated for a 40 that's what I would look for. No less than a 30 for sure. If money is an issue, why not look on the used market? You should not be swayed by your experience with you current motor, a good, late model used motor can be trouble free as much as a new motor.
 
An old boat rated for 40hp, would be rated at 30 at today's standards.. The motors of today ( since the mid 90's) are prop rated and old ones are crank rated.. I think you would be very happy with a 25 or 30hp.. 20hp is a little small for a 16 ft.

My new (2011) 16ft legend has a 30 2stroke and it has plenty of power.. A 25 would have been "good enough" but I think a 20 would have been too small. Btw.. My boat does 30mph with just me in it and no gear.
 
Thanks for the suggestions. I was wondering about the HP ratings of today vs. back in the 70's, so that was also helpful. Still haven't pulled the trigger, but it sounds like a bigger motor would be worth it.
 

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