Can I put a 75hp on a 50hp rated aluminum boat?

[Hardcoremfr]

I just got a 1987 bass tracker m16 aluminum boat and was wondering if it would be safe to put a 75hp on it even though it is rated for a 50hp. Kind of a newbie and this is my first boat bigger than a jon boat. Right now there is a 2010 15hp tohatsu and eventually that is not going to cut it for me. I've seen most of these boats have either a 35 or 40hp on them. But I have came across a pretty good deal on a 75hp mariner. I want to be as safe as possible. Thank you for any info

 

[Teamster]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

I want to be as safe as possible. Thank you for any info

Then you should follow the horse power rating,...........

 

[lakegeorge]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

No.

 

[Mel Taylor]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

Yes you can, but only at possible great risk to life and limb to yourself, to any passengers, and possibly to other boaters in your vicinity! Follow the manufacturer's guide and recommendations. To do otherwise would be just plain stupid.

Edit: I should have said "To do otherwise would be just plain stupid in my opinion".

 

[Home Cookin']

Re: Can I put a 75hp on a 50hp rated aluminum boat?

in some states you can get a ticket for going over. it might also be a factor that could jeopardize your insurance coverage.

 

[drrpm]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

You can do anything once. Most of the ones you've seen have 35-40 HP engines because that is an appropriate size for that boat

 

[bonz_d]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

I'd keep looking! With the added weight on the transom you will be bringing water in over the transom every time you have to idle down quickly.

My suggestion would be to look for a 50hp Johnson or Evinrude. They are some of the easyest engingines to work on and also have the most parts available. Next would be a 50hp Merc if you can find a good running one.

 

[H20Rat]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

I'd keep looking! With the added weight on the transom you will be bringing water in over the transom every time you have to idle down quickly.

Don't but the weight argument.. Yes, added weight is bad, but if your boat can't take an additional 20 pounds, you have other issues. A merc mariner 75hp with power trim is 268 pounds. A 50hp merc 4 stroke is 248 pounds. (Both including power trim) If the OP was talking about hanging a 4 stroke 75HP outboard back there, I'd have a different opinion. A 4 stroke 75hp is going to be in the 375 to 400 lb's area.

Also, outboard manufacturers have had a long history of manufacturing one engine and putting different carbs/exhaust on it, and rating it for a couple different HP ratings. Key point is that you can have 3 different HP rates, with 100% identical engine weights! (merc v6 2.5 liter blocks come to mind, identical engines rated from 150hp to 210hp)


As far as insurance, doesn't matter one bit... Also have yet to see a case where a mildly overpowered boat has had any legal issues. Think about it, if overpowering a vehicle would be such a bad idea, don't you think it would be far more of an issue with road vehicles? 95% of the diesel owners on iboats probably have a tuner which adds 50% or more horsepower to their truck!

 

[greenbush future]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

Weight is just one item to consider IMO. Extra power or speed could be just as dangerous and I believe it is also part of the manufactures ratings calculation stamped on the back of the boat. It would be wise to follow these ratings, and not exceed them. There are rare exceptions, but I don't think this is one of them.

 

[Pony]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

A) Poster has not had experience with even a small powerboat B) This isn't a small HP increase.....talking 50% here C) Like others have said, I don't think weight is the issue.

IMHO I think that in some cases going over hp ratings is probably not going to be an issue, but in this case I think a 16ft tin boat is going to be pretty susceptible to challenges from being overpowered. Sure you could just throttle back, but who does that? and why lug the engine for no good reason? If we are talking 2 strokes.....they like to RUN! My 14ft boat was rated for 25hp, and I thought that was borderline too much when I was the only one in the boat.

I would think there are TONS of motors out there in great shape in the 40-50hp range

 

[smokeonthewater]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

have yet to see a case where a mildly overpowered boat has had any legal issues.

150% of rated HP is not at all my idea of mild.... had he asked about 75 hp on a boat rated for 70 I'd call that mild

Think about it, if overpowering a vehicle would be such a bad idea, don't you think it would be far more of an issue with road vehicles? 95% of the diesel owners on iboats probably have a tuner which adds 50% or more horsepower to their truck!

Sooooo incredibly not applicable.... Road vehicles do not generally operate anywhere near the limits of control but boats do... Roads are flat and predictable and chopping the throttle suddenly in a pickup truck even with 10 times the factory supplied hp (notice I didn't say max rated because there IS no such number) will never result in the wake swamping and sinking the truck....


Road vehicles as I said above do not have max hp ratings so there is no number to exceed....

We DO however have limits in road vehicles... SPEED limits and last time I checked we can get in pretty big trouble if we exceed them


O/P My advice to you here is that GENERALLY the max hp specified for most hulls is at the upper end of what works well on a hull..... No an extra 20 lbs isn't a deal breaker usually IF you are comparing to the perfect motor for the boat but for best ALL AROUND performance (not top speed only) the max rated motor is already pushing it..... MANY boats will reach with just a few mph of the same top speed with 3/4 of the max hp but by shaving stern weight and cubic inches the plane better at lower speeds and get better fuel economy...... so theoretically if that 3/4 of max engine were 50 lbs lighter than the max and then you put another 20 lbs or more, a 70+ lb addition to the stern of a small boat CAN make a pretty big difference and MIGHT only gain you 5-8 mph.


Since you asked and said you wanted it "as safe as possible" find a 35 hp motor.

 

[Mel Taylor]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

If gas consumption is a consideration I would imagine that there would be a considerable difference in mpg between a 40 or 50 horse engine and a 75. My experience has almost entirely been with two cycle outboards in the 25 to 35 horse range so I'm posting this more in the form of a question than an opinion.

 

[bonz_d]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

No real experience here with Mercs but I know there is about a 50lb difference between the 60hp 2 cylinder Johnson and the 60-70hp 3 cylinder Johnson. To me that is a lot of weight difference which is the biggest reason I repowered my 16' Alumacraft to the 2 cylinder.

The Bass Tracker MV 16' is very much like a glass bass boat w/o a lot of freeboard and a flat deck covering the back of the boat. Which I've also just finished a quick search on and cannot find any specs.

An extra 20 lbs might not mean much but I would think an extra 60 lbs would. These are shallow boats, modified JON'S if ya ask me.

So in this case there would be no weight difference between a 40hp, 50hp, 55hp or a 60hp 2 cylinder OMC engines.

I wasn't even concidering whether the transom could support the extra hp because as far as I'm concerned that boat with a 75hp on it would be unsafe and unstable. It just doesn't have the beam.

Been on a couple that had 40hp Mercs on'm and they fly with just 2 people aboard.

 

[SigSaurP229]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

Nope I wouldn't even think of overpowering that much.

 

[MikDee]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

Have you had an aluminum boat before? There is no buoyancy in aluminum, like wood. If you throw a piece of aluminum into the water, it drops to the bottom, wood will float, and provide a degree of buoyancy for a certain amount of weight resting upon it. Aluminum just displaces water around it! That's the difference. Changes in weight distribution in an Alum. boat will produce fast & hard movement, if you're not prepared, you, or a passenger can get hurt or be thrown overboard. Amplify that by putting a too heavy, to powerful motor on it,,, that's why max weight, & horsepower is listed. The power, & prop torque on a 75hp motor is probably enough to roll you over if you happen to speed it up in a slow turn, because there is not enough beam on a 16' boat. Plus, any quick slowing down, may cause water to come in over the transom, and there's no stopping it if that happens, you could get swamped! Remember, that's on flat water,,, imagine choppy, or rough water!

Do you still want to put that 75hp motor on this boat?

 

[JimS123]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

This is one of the most frequently asked questions. The general consensus is always the same.

The "sticker" on the boat says "Maximum Rated Horsepower XXX". For goodness sakes, how hard is that to understand? If the Speedlimit sign on the side of the road said "55", would you ask an internet forum if it was Ok to go 75?

A common saying is that "there are no dumb questions". Well these types of questions don't fit that saying. (IMHO)

 

[pckeen]

Re: Can I put a 75hp on a 50hp rated aluminum boat?

First - WELCOME TO IBOATS! :welcome:

There is a ton of useful information here, and no shortage of people with advice. We were all newbies once, and most of us remember that (and remember our mistakes) well. Most are pretty helpful.

The only dumb question....is the one not asked....

GOOD question. Glad you asked. Glad you checked.

In my part of the world, there are a few people who overpower boats, largely because they want speed speed speed, but the broad consensus is this isn't a great idea. An overpowered boat increases the risk of a boating accident and means that you are over weight.

If I'm understanding you correctly, you have a 15hp motor on the boat now - that is significantly underpowered for that boat, so you will get very poor performance out of it. You will notice a massive difference in the boat with a 50hp motor on it. Good luck in your search!

In terms of your motor search, as a general rule of thumb, a boat should have a motor that is at least 70% of the max rated for that boat. In your case, that would be minimum of 35hp. If you put on a motor less than that, you will suffer performance wise. If you will regularly be travelling with several passengers plus gear, then you will be better off looking for a motor close to the maximum size.

In your search, remember that you will need to match the transom height of the motor, to the transom height of the boat.

What is the set up on your boat? Center console? tiller steering?