porta bracket

[jboatdoc]

I am in the process of closing in my transom on my 74 Seafari. Has anyone installed a porta braket?

[FELLOW-SHIP]

Hi jboatdoc

You need a flotation bracket on the boat the more flotation the better. Most guys will buy a bracket designed for either a very heavy single or a bracket for twins. You are moving the center of gravity from the original design back approx 24-30” on a boat designed for lighter motors. All boats were made that were 15-30 years ago.


FellowShip

Just for the Grins

[jboatdoc]

The porta bracket has a 21 and 17inch stand off. Why is the extra flotation needed. The motor I am using is a stock 150 merc 2.5 liter. I think the weight is around 420lbs and the porta bracket is about 50lbs. Do you think this will make a difference?

[Fr. Frank]

If you go with the porta-bracket, make sure you close the deck drains, and just use bilge pumps. Otherwise at rest you'll have a couple of inches of water on the aft deck. I agree with the recommendation for flotation bracket. The Seafari was designed for a maximum engine weight of 325 lbs, which was the max weight of an inline 6 Mercury including trim system. The design was not later modified to accept V6 motors in '76-'77. The assumption was based on a recommended OEM power of 90-140 hp.

[Bushwacker]

Ask Capt. Lloyd about the need for flotation tanks! He had a 140 Zuke 4S (420 lbs) on a 20 cc with a stainless marine bracket with a very small flotation tank. He went to a lot of trouble to build a big tank around it to improve static trim!

Even if you use a 300 lb motor, if you put it 17-21 inches further behind the boat, self bailing will probably be marginal. When you move weight aft, it shifts the boat CG aft . . . just basic physics. You'll need a flotation bracket if you want to have any hope of a self bailing cockpit with a 400lb+ motor. The Hermco bracket on my boat with 30" setback, has the most flotation of any bracket on the market, and with the 429 lb E-Tec, it's just barely self bailing! If the pockets above the scuppers on your boat are more than about 1.5" deep, you have a raised deck model (think they raised the deck in about 74 or 75) which will be a little better, but with no flotation tank, it'll still do exactly what Fr. Frank says!

Another thing you need to consider is that when you're up on plane, that flotation tank isn't doing anything to compensate for the aft shift in CG! It will adversely affect (increase) min planing speed, and that's a big deal in a 20 if you want to ride comfortably and avoid going airborne in rough seas! I had to add a Doelfin and go to a 4 blade stern lifting prop to get my min planing speed back down to the 12-13 mph range I previously had with the old 300 lb V-4 with no bracket! Although brackets provide more room in the boat, improve performance and offer the safety benefit of a closed transom, the balance issue with the newer heavier motors is a potential downside you need to be aware of!

[CaptLloyd]

Denny (Bushwacker) and Fr. Frank are spot on, for static trim/self bailing, a large floation chamber is a must! Also, a bracket shaped like a Hermco helps reduce bow rise coming up on plane.

On plane, no matter what style bracket you have, you must compensate for the CG shifted aft. Trim tabs work great, however, you lose alittle speed. A stern lifting prop will greatly help.

I have had the small chamber (virtually no extra floatation), and now the large floation chamber on the same boat/motor, and I'll tell you lots of floation is the only way to go.

FYI, mine is a 26" setback.

Good luck.

Lloyd