Upgrading from 2 stroke to 4 stroke

[Cdooer]

Hi there. I’ve got a 1998 16’ Lund Fishing boat, with a 60hp Yamaha outboard motor. It’s a great boat, has live wells, a windshield, etc. I inherited it a few years ago when my dad passed. We don’t fish a lot, but we do live pretty close to the water. My kids are getting a little older, and pulling the 14 year old on a tube seems to tax the motor pretty good. Would upgrading to a brand new 90hp 4 stroke (boat says that 90hp is the max) make it a little easier when tubing, or would we notice much of a difference?

 

[roscoe]

yes, but switching to a lower pitched prop could likely do it for under $300.

Does the boat have a tach?

If so, what are the wide open throttle rpms with the current prop?

What is the size and pitch of current prop?

 

[alldodge]

Finding a 90hp 2 stroke (Merc 306 lbs) will provide more power because the 4 stroke additional weight of 360 lbs. The 4 stroke will provide more power then the current 60 weight of 238 lbs

Compare weight to see how it can come out.

 

[Cdooer]

yes, but switching to a lower pitched prop could likely do it for under $300.

Does the boat have a tach?

If so, what are the wide open throttle rpms with the current prop?

What is the size and pitch of current prop?

Unfortunately the boat doesn’t have a tach. I’m not sure about the prop either...I’m guessing it’s whatever came on the boat. My dad didn’t buy the boat brand new, but it had it quite a few years, and I don’t remember him ever changing it out.

 

[Cdooer]

Finding a 90hp 2 stroke (Merc 306 lbs) will provide more power because the 4 stroke additional weight of 360 lbs. The 4 stroke will provide more power then the current 60 weight of 238 lbs

Compare weight to see how it can come out.

Does anyone still make a 2 stroke? Maybe Evinrude?

 

[alldodge]

Does anyone still make a 2 stroke? Maybe Evinrude?

Not that I'm aware of, but there are good used 2 strokes out there. Heck I have 3 good Chrysler motors

 

[Sea Rider]

If wanting to get the max fun out of that combo need to buy a cheap induction tach, install it, program the spark plug firing sequence, go for a wot run as loaded and report max wot rpm achieved on flat calm water cond. Need to know which pitch is currently installed to go from there to less pitched props to pull wot revs higher assuming the motor is over propped for top pulling toys application ?

The wot rpm range for those 2T 60 HP Yam's is 5000-5500, ideal would be for the motor to rev to at least 5250 rpm, if wanting a faster hole shot towards max 5500 rpm. A tach along a correct prop maximization is the way to go so as not to be tempted going for 4 strokes motors.

Yamaha, Suzuki, Tohatsu still manufactures lots of 2 strokes motors in their respective HP range, the issue is that are banned in many countries....

Happy Boating


​

 

[JimS123]

Does anyone still make a 2 stroke? Maybe Evinrude?

Evinrude is out of business. No 2-strokes available in the US except used. If the motor runs Ok, fix the prop. If not buy a 60 HP 4-stroke and fix that prop and you'll be happy.

(fix prop = follow post #7.

 

[ahicks]

Another vote for getting the 70hp motor set up properly to pull a tube.

I think a 90 hp 4 stroke is going to totally overwhelm a typical 16' fishing boat....

 

[QBhoy]

The thing about a new 90hp merc is that it’s the same engine as the mighty 115hp merc. In that power, it’s a very light engine for its huge displacement of 2100cc and actually puts out a good deal more power than its 115 badge suggests. It’s lighter than a 125 optimax 2 stroke and more powerful too.
but in it’s derated 90hp form...it’s not that terribly light weight compared to a 2 stroke of the same power. This means it’s not as attractive perhaps. You will notice a huge difference in performance even with the 90hp...but I’d think the enormous cost of doing this would be a little silly on occasion...as great an engine as it is. If it’s just for towing...get another prop. If your boat can take e extra power of the max rated version of the merc 4 stroke (115hp but actually more closer to 130hp in reality), it would be silly to just get the 90hp restricted version, I’d say. Lots to think about I suppose.