Max H.P for a 20' Seafari.

[bigeasy1]

I've been kind of looking for a used outboard for the 20' Seafari I recently aquired, to replace the seized up 150 Johnson that's on it.

My question is that the Original Seacraft capacity plate says max hp is 140 hp.So let's say that I get stopped by the Coast Guard for what ever reason,will I be in trouble for running a power plant in excess of the capacity plate?

If the above is a non issue,then what would you think is the minimum and maximum horse power limits for this 20' Seafari.I would most likely be going with a two stoke for the weight savings.
I really don't like the low transom,so I'm going to fabricate some kind of raised splashwell tub to keep the water out.I did contact Don(HERMCO)and he still has the mold for it,but as he said,it would cost as much as I paid for the boat.
As much as I'd like to have him make one up,and i thank him for getting back to me quickly,but I can't justify the expense.I'd also like a new E-Tech for it but that's not going to happen.
I just want this to be a reliable bang around boat for some inshore fishing in the salt water.
for whatever I can catch.My Tsunami is my serious fishing boat.

I will say however,that I really never cared for the looks of the Seafari,but now that I see it in my yard every day,I've come to love the looks of it.

[FishStretcher]

If you put an anchor roller or pulpit on the bow to make the length over 20 feet, then I think you can get around the capacity plate? Or at least recalculate it?

I think a few others here know more about this.

[otterhound]

I have a 1979 Seafari here and it says 175 hp max on the capacity plate.
Rod

[bigeasy1]

Originally Posted by otterhound

I have a 1979 Seafari here and it says 175 hp max on the capacity plate.
Rod

Interesting, I wonder why the difference? mine is from the early seventies,there is no Seacraft factory hull ID # but there is a Massachusetts certified hull number on it that says 1971.
I know very little about these hulls,so I wonder why the different rating.The capacity plate is riveted on and is,I'm sure an original plate.

[Fr. Frank]

Yup, over 20', there is no legal limit to the horsepower you can hang on the back. Just add a bow roller, or a swim platform to get over 20'.

HOWEVER, the 20' hull (19'8" actual) was designed for an outboard motor weighing LESS than 300 lbs.

I've put a 245 hp motor (Merc 2.4L Bridgeport) on the back of one, and I've rigged them new with just 85 hp. I had 200 on the back of my own Seafari before changing to a 90 hp Optimax. Fuel economy with the 200 was just under 2 mpg. Fuel economy with the 90 Opti was about 6 mpg. Cruise speed with both motors was 23-25 mph. Top end with the 200 was about 50 mph, with the 90 about 35 mph.

I think the late 80's Mercury inline 6 cyl 2-stroke 115/140 hp or the late 80's through late 90's 115/130hp V4 Yamaha's are great for the 20' SeaCraft. These are older lightweight motors with plenty of power, and you can find really good freshwater used motors across the upper mid-west.

[Fr. Frank]

Originally Posted by bigeasy1

Interesting, I wonder why the difference? mine is from the early seventies,there is no Seacraft factory hull ID # but there is a Massachusetts certified hull number on it that says 1971.
I know very little about these hulls,so I wonder why the different rating.The capacity plate is riveted on and is,I'm sure an original plate.

In 1971, 135 hp was the most powerful outboard made. The 1st 150 hp didn't appear until late 1972. Rating it for 140 simply meant that you could put any motor you wanted onto it, without fear of overpowering it.

[otterhound]

Not sure but I have a 25" transom (which sadly needs replacing lol) on mine. If yours is 20" that could be the difference.
Rod

[gofastsandman]

My 89 20 cc is rated for 235hp because it was the biggest at the time.

[Bushwacker]

Originally Posted by Fr. Frank

I think the late 80's Mercury inline 6 cyl 2-stroke 115/140 hp or the late 80's through late 90's 115/130hp V4 Yamaha's are great for the 20' SeaCraft. These are older lightweight motors with plenty of power, and you can find really good freshwater used motors across the upper mid-west.

I would add the OMC 60 degree V-4 loopers (Maybe 100-140 hp?) to the list, but nothing later than about '95-96. I'd be concerned about quality problems related to the death spiral they hit in '97-98, especially on a low time motor;a higher time motor might have had any quality issues fixed under warranty. The carb'd Johnsons made BRP starting in 2000 would be the best quality version of that design. I had an older 1975 crossflow V-4 that was a simple bulletproof motor that I ran for over 30 years, but they were loud smokey gas guzzlers. I averaged 2.8 mpg over 6 Bahama trips carrying very heavy loads. One advantage of a 20" transom is that there are probably a lot of fresh water motors available in the 20" size!

Capt Terry repowered his '76 Seafari with a 20" 150 E-TEC. It's heavier than his old Merc, so he made some sort of dam to close up the cutout and I think he was experimenting with a "Vortex" duckbill-type check valve to keep water out of the splashwell. Maybe he can post some pictures of what he came up with.

BTW the capacity plate on my 72 Seafari lists max hp as 170, which I think would represent twin 4 cyl 85 hp Mercs that were available back then, but Fr. Frank is right, the 20' hull performs best with a light motor of about 300 lbs or less. Since the Seafari has more weight forward than the CC models, it will tolerate a heavier motor better than other models.

[Capt Terry]

As Bushwacker remarked here is a photo of a dam for my 20’ Seafari after replacing a 1985 Merc 150 with a 2013 ETEC 150 HO (about 43 lbs heavier). The ETEC has been raised twice (probably needs to go up once more) and it seems higher than my Merc; hence the idea of the dam. I did not intend the dam to be water tight, but primarily avoid waves when folks are sitting or standing in the stern. I glued PVC house trim together to get the final height. A left and a right half enable them to interlock under and be installed without engine removal.

As for the splash well drain hole the jury is still out on a slit, nitrile glove finger attached to a short piece of stainless tube. Didn’t notice much water in the splash well yesterday, but maybe just didn’t have any heavy-weights with me!

I have been a boater over 50 years and never heard as much chatter as the last couple years about engine height. And it’s usually raising, not lowering them. It makes one wonder what has changed and about raising transoms to provide more freeboard. I added a Potter-built SeaMark splashwell a few years after the boat purchase. So I don’t sweat it too much. But, with the engine shutdown and in certain sea and wind conditions have had water lapping over the transom and wondered if this might have been the situation for the two Jupiter boys. My ’76 Seafari with a Merc (eventually replaced with an ‘85 Merc) were all purchased from and rigged by Frank Brown (Moesly’s former race mechanic), so guess it was no surprise Frank did it properly. My ETEC dealer, who mostly deals with bass boats and pontoons, had never seen a SeaCraft.

In the photo you may also notice a wooden contraption I made to tilt the engine higher when towing with my low-slung Hitchhiker trailer.