I had the exact same motor set up as Jwclbi on a 20' Sceptre no Bracket but on a 4" setback jack plate... Loved that boat should have never sold it. Ran like a Scalded ape, Handled Great and Kick Ass fuel Economy...

That 175 pro xs puts down about 190 hp at the wheel.... U can run anything up to a 250 IMHO without issue... My EFI weighed in at 475 lbs and put down 245hp at the wheel...

Hang the power on you won't be dissappointed.

Just my 22 Cents
Robert

Hey there Gameon do you remember what your boats speed was at full throttle?

I ran a 1991 Mercury XR4 2.4L on the back of my old '72 Seafari. Originally 175hp, after rebuild it produced about 210 hp. I had a Bob's nose cone on a lower unit from a 225 Merc, low water-pickup, and ran the motor fairly high on the transom, turning a one-of-a-kind custom 3 blade prop from Power Tech, 15x16.5P

My maximum speed (with everything just right) was 53 mph at 6050 rpms. But everything had to be perfect to get that speed: minimum weight and minimum windage, air temp below 50*, low humidity, running into an 8-10 mph wind, moderate chop to get more hull out of the water, etcetera.

Most of the time I couldn't get over about 47-48 even with the higher hp. And I normally never ran over my 25-26 mph cruising speed because of fuel consumption with a 29 gallon tank.

So I repowered with a 90 Optimax, and went from less than 2 mpg, to nearly 7 mpg average. I loved it.

In 1969, the largest Mercury outboard was 125hp and it weighed 270lbs. The 20 seacraft hull was NOT designed for heavy modern power. You have to slow down to a 18 - 22mph cruise when the waves hit 2ft. When it's flat calm, the top speed for the hull is in the 50's before it starts to walk. Check out a merc 115 4 stroke or something under 400lbs.

Just looking over the 1974 pricelist. If weight was an issue, why were the 20's offered with so many different v8 sterndrive options? Those small blocks must be close to 7-800 lbs with the drive and steering.

Marketing?

Why indeed.

A good portion of the I/O is forward of the transom.

Think teeter totter.

CG is much more important than weight, ie., it's all about where the weight is located. Carl Moesly told me that the CG on an I/O Seafari with the 4 cyl MC is further forward than it is on the OB version with a 300 lb motor on the transom! I think those V-8 I/O's are closer to 900 lbs, but the CG would probably still be further forward than it'd be with a 500 lb 4-stroke hanging on the transom!

Could be.
Could be.

He understands much more than most of "We".

Vortec with 71C is 900lbs, with an I/O probably over 1000.

I used to see a gal and her young squids in a 4 cyl version. For a bit.
And then they would pull away into the sun.

I guess I need to get me some Lencos.