Remember, this group is dedicated to the preservation of old outboards!

An old engine rated for 30hp at the crank might deliver 24 to the prop.

You didn’t say how much you use the boat, and what condition you keep it in.  I ended up here because I bought a vintage boat, and vintage power was a no-brainer in terms of price, and keeping the boat period correct.   But I spend more time tinkering with the boat than running it.  If I used it every day, I might feel worse about what the engine spews (and/or the cost of biodegradable oil).

Parts are available, and your old engine is a testament to a time when things were built to last, and OMC made engines that ordinary folks can work on with ordinary tools.

It sounds to me that you have a family treasure, and a young fellow that appreciates it going into the next generation. Keep it as is, do simple maintenance and it will be around for another generation.

Joe B

PS, looks like you found the right organization … be sure to hook up with a local AOMCI chapter, lots of help , parts and admiration there.

PPS, how about some pictures?

I don’t have thrust numbers, etc, but your 30 HP, being a 2-stroke with fairly large cylinders, will likely provide noticably more low end torque for getting planed off and pulling up skiers than a new 4-stroke, as with 4-stroke engines only firing on every other piston stroke, they don’t have the oooomph on the low end. A new Yamaha 25 4-stroke with it’s HP rated at the prop, with the correct propeller, should give you about the same top speed, and will use a lot less fuel. In recent years, Yamaha has redesigned their 25 HP 4-stroke and reduced the weight. Other brands tend to be heavier because they go to 3 cylinders to get 25 HP or more. The 146 pound weight is not that much heavier than your long shaft 30 HP . Short shaft 30 HP is 113 pounds, so long shaft is about 120 pounds. I have a few 30-35 HP motors from the 1950s, and on my pontoon, have a 25 Yamaha 4-stroke (my wife wanted the quietness of a 4-stroke there after riding a neighbor’s 4-stroke pontoon), so I’m familiar with both motors. My personal preference would be to stay with your Lark, unless it’s a heavily used boat where quiet, reliability, and low fuel consumption are a high priority. If you pull a lot of skiers and tubers, the Evinrude will be better….but going to a lower pitch prop with the Yamaha, and/or dropping the trim pin down will make it easier to pull up skiers, but these items will give you a bit less top speed. With the Yamaha you will need adapter hardware to use cable and pulley steering, and I don’t know what all that involves; otherwise, you will have to get a new steering wheel with today’s single cable steering setup. The Yamaha will have an alternator, which is a plus if you don’t have the generator kit on your Lark.
Dave