Sceptre 20 I/O Repower

[ericallen01]

Hello CSCers

Been running my 1975 SC20 for a season with an 1990's 5.0L/Alpha One setup. It's a great hull, is nicely powered and handles well on plane. I put on Bennett Tabs also to improve planing.

However the engine weight (est. ~940lbs with outdrive) seems a bit much for the hull. The boat sits stern heavy, with the stern cockpit sitting 1-2" below the waterline. I'm not too confident to leave the boat moored overnight with the scuppers open. Boat is otherwise stock.

With the hull + transom in great condition, I'd like to do a sterndrive repower and wondered if anyone had looked at weight-power in the I/O category for these hulls.

I did see some V8 options in the SC catalogues for 20' hulls.

Today, the 3.0L vs. 4.5L seem like the most relevant options, but I'm open to advice.

Would putting in a 3.0L leave me seriously underpowered?
Is the V6 a poor tradeoff to save 120lbs?
Are I/O's a poor choice today for these hulls given outboard/bracket combos?

Thanks in advance!


Advertised Mercruiser engine weights (excl. 70lb alpha one)

Reman
350 MPI Alpha 932
357 Alpha 4V 871
4.3L Alpha 4V 784
3.0L Alpha TKS 567

New
4.5L 250hp ECT 761
4.5L 200hp ECT 761
4.3L MPI ECT 220hp 775
4.3 TKS 725
4.3L MPI ECT 180hp 775
3.0 TKS 455
3.0L MPI ECT 515

[Capt Terry]

You may want to search for and consider my post "Estimating CG Shift with Heavy Engines". Terry England, with respect to I/O's versus outboards, want to chime on on your twin ETEC's on your 25' Bertram?

[Terry England]

Originally Posted by Capt Terry

You may want to search for and consider my post "Estimating CG Shift with Heavy Engines". Terry England, with respect to I/O's versus outboards, want to chime on on your twin ETEC's on your 25' Bertram?

Yea, I don’t think I’d put a car engine with two 90- degree turns back in the 20’ SeaCraft. Probably OK in a 23 if you like “wrenchin” on your boat or paying someone to keep everything together. In my opinion, today’s stern drives are better than they ever were, but outboards are WAY better than they ever were.
Everybody builds great outboards in the 115 - 150 range and realistically that’s all you ever need on a 20, unless you want to race. I run a 90 on my 19’ stripped down SeaCraft Bowrider and it does fine. I think if you want to race, do it in flat water - sell the SeaCraft and get a Talon.

The 20’ Seacrafts “dance” over the water if you keep them light. The 25 Berts “plow” a 10 wide, 24 degree slot in the ocean where ever they go when you run them loaded with dive gear like I do. In my case two 15” diameter props have more surface disc “push” than a single 21” wheel surface area. The Berts are actually narrower at the transom than they are amidships where they are almost 10’ so if you hang too much weight in the aft portion they will squat with their ducks ass. I wanted twins for going way offshore but needed to keep the weight down so I took the sterndrives out, shed a 1500 lbs and used a couple of light V-4, 115 E-tecs.

The winds look under 10 mph this Saturday so were are taking the SeaCraft out about 28 miles to see if we can find a couple of groupers before the season closes. My fuel burn for the day should be about 16 or 18 gallons for the day.