There's no argument, the 175 should be plenty fast and is a perfect fit for the 20 SF. I currently have a 94 Evinrude 150 that runs great and tops out at about 45 WOT. But me personally, I'd like to see at least another five miles an hour top end, additionally I come from a family if big people and have some pretty darn big friends too. So the extra horses comes in handy when you're hauling around a lot of meat. Whether it's Justified or not, I guess at the end of the day the real answer is, just because I want it. :-)

Remember you from Hommasassa and you are a big guy. If thats want yiu want that is reason enough. I am raising my transom to accommodate occasional large guests. Go for it!

Got it but have no clue
 

After the seller going dark on me, I got a call back and he made me an offer that even Spidercrab couldn't pass up. So now the 175 is sitting on the floor in the shop and has been for like a week while I figure out if i'm gonna pull the boat apart and now do the re-coring, close in the transom completely, hang the new full flotation bracket I bought 2 weeks ago and then rig the new engine or If I'm going to install the bracket and the engine run it for a bit and find and plan the proper balance and COG before I tear it apart and re-core it and do moderate but through refit to include live well and a trolling gps anchor system. I'v got a ton of question that I'll be asking soon. After I get everything done for the day, I'm back in the groove of late nights falling asleep at the computer while reading up on my future itching fits.

CG Shift
 

Ryan-
If you haven’t seen it I made a post, think it was 9-24–16. Subject was estimating CG shift due to heavy engines or brackets. A way to apply numbers and some science to reduce quess work and to experiment with temporarily placed weights. There are some good additional remarks by Bushwacker and others. Best wishes.

Hermco Set Back
 

Thanks Terry, thats good stuff. I'm still trying to absorb it a little to where I can see it in my head 3D at the moment its still a little clunky upstairs but it has all the basics needed to dial it in.

Do you know the set back of the Hermco bracket..26?

Does mounting height of bracket (within standard reason) have much if any affect on its value as a lever arm?

I imagine I am giving myself plenty of wiggle room with my 12"x12" trim tabs (provided I go ahead and set it up as close to COG as I reasonably can), but are there any other considerations I should should make because of the tabs?

Lastly, what if ... someone... were to also have a hydraulic jack-plate adding an additional 6"inch set back (taking that into consideration for the lever arm too), any thoughts on pros or cons or comments? (someone we all know recommended I do jackplate on bracket with a good argument but I really think he just wants to see someone do it for the sake of experimentation, while he sits back, has a smoke and watches Frankenstein build a monster..

Ryan=
Sorry for the delay, I was out of town.

I used 2' for the engine location on a Hermco, don't remember if this was a guess or from Bushwacker.

There is also a vertical component of cg, which I ignored. I would expect little effect of engine height on the longitudinal cg. However with the length of the bracket you may need to raise your engine higher than you expect to get the AV plate on top of the water. Check for other posts on this. Bushwacker added a mechanical jack plate to his, for this very reason.

You asked about the additional effects on your cg if your 175HP ETEC were mounted on a hydraulic jack plate in addition to a bracket. I returned to my CG Change Estimator posted on 9-24-16. I used the “original example” except changed the hull weight from 1800# to 1600# and 418# for the ETEC to get a baseline cg of 4.8’ fwd of the transom. (This may not be where yours is, but we are talking changes here, so read on). Then for using the ETEC on a 200# bracket with the engine 2’ further aft the estimated cg is 3.9’ fwd of the transom or about 11” further aft with the bracket (similar to the results Bushwacker experienced when he put his ETEC 150 on a Hermco bracket. Then I considered the engine 6” further aft on a 50# hydraulic jack plate attached to a bracket which put the cg at a minuscule 1” further aft then without the jack plate. I think you mentioned your boat guests are hefty, so they may even compensate for the bracket mounted engine. Move them around to judge the effects. Bob Reiland who may have made 50 Bahama crossings on his SeaCraft 21’ Unoho didn’t have trim tables; he just moved people or cargo around to adjust trim.

Sorry Ryan, the 2' mentioned above was to the cg of the bracket. My example calculations were that the engine cg moved from 0.5' aft of the transom to 3' aft when on a bracket. Better let one of the Hermco bracket owners chime in on this. My examples were intended to be illustrative of the cg technique, not absolutes.

Thanks for all the info Terry, I've been tied up and haven't done anything yet, but we'll see if any bracket owners chime in.

On Bushwacker's old Seafari the bracket is 30" from transom to the back of the mounting plate measured along the swim platform. The manual jack plate is a touch less than 4". So the motor is moved way back behind the transom. Without trim tabs it can and will buck hard. By comparison, my yellow '78 with 175 Black Max on the transom was smooth with just engine trim.

I would be looking at 32" over all. What do you mean by "buck hard"?