1977 18sf vs 2003 20sc

[dginge]

Has anyone owned a potter built 18sf (I have a 77) and then bought a 20sc manufactured in the 2000's? I'm just curious of the ride differences ..... I'm thinking about an upgrade. The 20sc has a 4stroke yami and it's got my wheels spinning. I also like the bow space for family and fishing. Storage sucks on the sc though! Thanks

[PigSticker]

I had a 76 18 and an 05 20. Hard to make a comparison giving two different set ups. The 18 had a 140 no tabs, the 20 had 200 hpdi and tabs, the tabs alone made it ride like a bigger boat in a chop, and it was quick. I would suggest taking a ride in the 20 on a windy day and then you can decide.

[Bushwacker]

Originally Posted by PigSticker

. . . Hard to make a comparison giving two different set ups.

I agree, the key to a soft ride is good balance. Trim tabs can help compensate for a stern heavy situation, but they'll add drag, increase fuel burn and reduce speed. I've ridden in the 18 Snookerd had with a 130 hp 2-stroke that rode very well and I don't believe it had trim tabs.

The key metric to test would be the min planing speed on both rigs w/o using trim tabs. All of Moesly's designs (the 21, 19 Bowrider, 20cc and Seafari, 27 Seamaster and 25 Seafari) with original power (~300 lb motors on the OB models) seem to plane at about 12 mph, but min planing speed will increase as motor weight increases. I would bet that an 18 with light 2-stroke power will ride better than a 20 with a ~500 lb 4-stroke on the transom. I speak from experience because my boat rode better with a 300 lb motor on the transom than it did with a 430 lb motor shifted 30" aft on a 150 lb bracket. Min planing speed went from 12 mph to 22-23 mph! By adding trim tabs, a Doelfin and a stern lifting 4B prop, I got it back down to 12 mph but at some penalty in speed and fuel burn.

And if you want more storage, take a look at a 20' Seafari or Sceptre!

[dginge]

Ok...I'll be more broad. how Does the 20 ride overall with a 4stroke 150?

[dginge]

Thanks Bushwacker

[Bushwacker]

Originally Posted by dginge

Ok...I'll be more broad. how Does the 20 ride overall with a 4stroke 150?

Those motors are at least another 50-60 lbs heavier than my E-TEC (be sure to compare WET weights, with full filter & 6-8 qts of oil in the crankcase!). If it's hanging on the transom with a 3B prop and no fin, I'd guess it would perform about like mine did originally before I added that stuff, i.e. min planing speed in the low-mid 20's. If motor is on a bracket and they didn't move the console/batteries/gas tank forward to rebalance (an option I didn't have in the Seafari), I suspect it'd be worse.

One clue as to how well it's balanced is how deep the chines are immersed at the transom at rest. First 2 pics below show how mine sat with 300 lb motor with full and empty gas tank. With an empty tank, transom chine was maybe 1" deep, with trim tabs almost at surface, and maybe 2" deep with a full tank (Pic 1 & 3) . In last pic with bracket and new motor, chine is 4.5-5" deep. (35 gallons). The 2" bootstripe is in same location in all pics, just repainted w/new motor. Remember that the Hermco bracket has a lot more flotation than the typical Armstrong bracket, so it probably offsets most of the motor weight. I suspect waterline would be similar if motor was hanging on transom. The big CG shift doesn't show up till you get on plane and flotation tank is out of the water!

[dginge]

Thanks bushwacker
It doesn't have a bracket. It has trim tabs though with a 2006 Yamaha 4stroke. Looks like that outboard is 500 pds with oil.

I plan on sea trialing her this week. I'm very interested to see the ride variances. Emotionally I will have a hard time letting the 18 go but I'm head over heals for a 4 stroke. We use our boats every weekend during summer. Thanks again

[Bushwacker]

Originally Posted by dginge

. . . I plan on sea trialing her this week. I'm very interested to see the ride variances . . .

Before you launch it, look to see where the waterline is on the transom and if it has a fin and 4B prop. If not, figure you'll need to add them!

During the sea trial, pull the tabs up and pay close attention to how slow it will run and stay on plane as you throttle back, as that will tell you if they shifted gear around to offset the weight of that heavy motor! Then try it again with the tabs down to see how much they help. Don't know what sort of seas you're used to running in, but the 20' hull is relatively light and will start to go airborne in 3' seas at around 20 kts, so being able to hang on plane at 12-15 mph is a big deal if you plan to run offshore very much!

[76Red18]

A properly set up 18 will ride just a liiittle bit better and be a liiittle bit drier than a properly set up 20. You'll regret getting rid of the 18 just like everyone else thats had one...

[dginge]

It is a myth to me if that's the case. Dry hull weight on 18 is 1400 pds. Dry hull weight on 20 1600. Beam is one inch different. 2 feet should make the boat ride better. I guess I'll find out soon. Will let you know.