Upgrading My Boat Engine

[Bradster314]

Hi, I have a 19 ft Plancraft sabre currently with a 90hp straight six Mercury 'tower of power'. I have found a 150hp Mercury V6 2 stroke for a good price. I'm not sure about fitting this to my boat because of the increase in power and possibly weight. Would there be anything i can do to strengthen my transom and anything to prevent the boat from being at a deeper water level at the rear.
Cheers

 

[sbooy42]

Re: Uprating My Boat Engine

Re: Uprating My Boat Engine

Not much you can do about the weight but you could add knees from the stringers to the transom for strength....

that boat looks fast just sitting there

 

[metriccrescentwrench]

Re: Uprating My Boat Engine

Re: Uprating My Boat Engine

What's the max HP rating for your boat? Off the top of my head I'd think a 19 ft. boat would be rated for more than 150, but only your data plate knows for sure. IF your boat's rated for that, and IF the transom is free from rot or other damage you should be good to go. As far as how much lower it will sit in the water, find out what the two engines weigh (NADA used to list engine weights, not sure if they still do) and stack that much weight on top of the 90 (not while you're moving !!!) to get an idea of what the added weight will do.

 

[Chris1956]

Re: Uprating My Boat Engine

Re: Uprating My Boat Engine

Brad, I would think a 19 footer would handle a V6 easily, although that boat does look a bit down in the transom area. The V6 will weigh 100#+ more than the IL6. The power of the V6 will be awesome. If you and a friend walk back to the splashwell, does she take water over the transom? If not, and the max rating is not exceeded, I would vote "go for it".

BTW- on my 16' Avenger, I changed out my Merc 1500 IL6 for a Merc 135HPV6. The weight is a bit much, but the V6 power is real nice...

 

[Bradster314]

Re: Upgrading My Boat Engine

Cheers for the advice, I just found the hp rating riveted to the boat and it says 80 - 85 hp :/ Maybe adding the knees is a good idea. Just found out that my Dad has another exact outboard as the current one another 90 IL6. He's thinking about putting the two on the back.... noy a good idea i'm thinking. Haha 180hp could be fun.... perhaps not when it all goes wrong

 

[Bamaman1]

Re: Upgrading My Boat Engine

Let me throw another wrench into this equation. Sometimes in the early 80's, there was a change in all outboard horsepower ratings. I had a 1979 Mercury Black Max 175 hp that ended up being a 150 hp motor after the change. I remember Johnson had a 4 cylinder outboard that ended up an 88 hp.

I assume the industry switched from a powerhead hp to a prop hp rating.

Wouldn't boats produced before the horsepower change show engine ratings to be lower than after the ratings change? The hull in question appears pretty old--and was a high fashion hull for its time.

My question is how does this boat handle a 90 horsepower. How fast will it run? Does it chine walk and get "squirrely" at high speeds? Is it stable, or does it skip across the water?

If you're getting 55 mph out of a 90, you'd probably just want to go up one size--115-135 hp motor. The 150 hp motors get pretty mean on a relatively small, lightweight hull. If you're just getting 45 mph out of a 90 and it handles well, go to a 150 hp.

Dual motors are out of the question, however.

 

[CaptOchs]

Re: Upgrading My Boat Engine

I'd say 100 HP tops.. Anything higher and you risk being a target for the coast guard or sheriff. It's also a safety concern. I would totally rule out the 150hp. Your boat just isn't designed to handle it. You could end up busting your transom and ruining your boat. If it's 80/85 hp max rating technically you're overpowering it with the 90 you have on it now. A random coast guard inspection could result in a ticket. It's been awhile since I read one, but some boat builders guides go through the mathematical equations for determining your max HP rating.

 

[Bartine]

Re: Upgrading My Boat Engine

It's only going to be 50- 70lbs heavier. I say run it, if your boat is rated for it. Its a 19 foot boat, should be no problem.

 

[Bartine]

Re: Upgrading My Boat Engine

I take back my last post. A quick google search tells me that the Plancraft Sabre is only a 16"7" boat with a 5' beam and weighs in at less than 700lbs. Max HP is 125. I wouldn't go over a modern 115hp.

 

[Bamaman1]

Re: Upgrading My Boat Engine

I'll also agree about the 115 hp max engine. They're reasonable to buy and are very efficient on fuel. This boat is a fly weight, and should perform very well with this size motor.

 

[Bradster314]

Re: Upgrading My Boat Engine

The boat performs extremely well at speed and is really stable at sea. We have just got a 115hp engine block which will replace the 90hp engine block.... perhaps this is the better solution. However thanks very much for all your suggestions and opinions. With the 90hp and a 17 pitch prop the boat will reach 50mph so hopefully with a 115hp block and a 19 pitch prop i will get a better top end