Bracket set-back question

zach · #1 02-08-2008, 11:39 PM

This is something I've been thinking about for a while and figured I might as well get everyones opinions. I am putting a bracket on my 20 and for power I am putting on a Merc 175 optimax. The standard bracket has a 30" set-back but I have read where people wished they had gotten a 26-28" set-back. Strick, on his beautiful restoration, built a bracket with a 25" set-back (granted he put on a v-4 engine). So here is my question, what do you think is the shortest bracket I can get and still have the Opti trim all the way up without hitting the stern of the boat?

Thanks in advance.

Tsunami23 · #2 02-09-2008, 08:06 AM

I'm no expert on this, especially with the 20', but I would expect that so long as you get a bracket with enough floatation to offset the additional moment arm from having the engine 30" vs 26", longer is the way to go. Most everything that I've read indicates that a longer bracket (given it has enough floatation) acts like an extension of the boat and generally improves the overall performance.
I'm just finishing my project (23' with 30" bracket - by Don Herman @ www.hermco.net). I pick it up this morning so I can't say for sure how it'll perform. Just my two cents. Good luck.

strick · #3 02-09-2008, 10:35 AM

There should be some specs/diagrams that show how much clearance you need for that motor. On the smaller boats keep the set back just enough to get the engine tilted up. A 25 inch set back should leave enough room to tilt up a Suzuki 140 4 stroke. Not sure what a 175 opti needs. Good Luck

strick

strick · #4 02-09-2008, 10:43 AM

Quote:

I would expect that so long as you get a bracket with enough flotation to offset the additional moment arm from having the engine 30" vs 26", longer is the way to go. Most everything that I've read indicates that a longer bracket (given it has enough flotation) acts like an extension of the boat and generally improves the overall performance.

Flotation only matters when the boat is at rest. When the boat is underway at planing speed your bracket provides no flotation what so ever. Moving the engine back 30 inches makes a big difference in how your boat will perform. Some things good and some things bad. Make sure you have trim tabs on your boat and you will be fine.

strick

Bigshrimpin · #5 02-09-2008, 01:15 PM

The bracket on my boat has a 26" setback and I can tilt my v6 Merc with an 175 XRI bucket style cowling all the way up with room to spare. Strick found some drawings on the internet for the suzuki 140 and those measurements were used to design the bracket. If I remember correctly you only need 22 or 23" radius from the tilt tube. Because the transom angles back at a 12 or 14 degrees (or whatever) . . . you need to factor that in b/c it can cut into that arch/range . . . so 24" - 25" setback is about as short as you can go.

zach · #6 02-10-2008, 04:44 PM

Quote:

There should be some specs/diagrams that show how much clearance you need for that motor.

Would Armstrong have this? I called them the other day about it and while they were more than willing to make a custom bracket, they did not know how far back it to tell me.

Quote:

A 25 inch set back should leave enough room to tilt up a Suzuki 140 4 stroke.

Just eyeballing, it seems as if the Suzuki 140 is about the same height from the holes as the Merc 175 Opti. Strick, how much room do you have between the top of your 130 and the transom? And is there anything else I need to take into consideration when sizing the bracket? Rigging? I imagine the main concern is whether the engine tilts all the way up or not.

zach · #7 02-10-2008, 04:47 PM

Quote:

The bracket on my boat has a 26" setback and I can tilt my v6 Merc with an 175 XRI bucket style cowling all the way up with room to spare.

I think 26" might be the way to go. I'm looking for those plans that Strick found.

Thanks Strick and Big for your help.

Bigshrimpin · #8 02-10-2008, 10:35 PM

I talked to Strick this afternoon. Apparently Warthog was the source of the 140 diagrams.

strick · #9 02-11-2008, 12:37 AM

Quote:

how much room do you have between the top of your 130 and the transom?

I have 6 inches of clearance when tilted all the way up.

strick

CaptLloyd · #10 02-11-2008, 09:05 PM

Zach,

I'm not near my boat, so I can't give you an exact measuement, but I have a 26" set back on my B-Bracket, with a Suzuki 140 4 stroke, and there is plenty of room to tilt the motor all the way up.

And like Strick said, be sure to have trim tabs. I find they get rid of porpoising (one of the few down sides to adding a bracket).

Lloyd