2007 Etec 175 Questions

[Capt Terry]

Originally Posted by Rybones

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.

[Capt Terry]

Originally Posted by Capt Terry

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

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.

[Rybones]

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.

[jtharmo]

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.

[Rybones]

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

[jtharmo]

Originally Posted by Rybones

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

Porpoising if I use no trim tab at all. I don’t have a fine touch with trim so I’m sure I start with too much until on plane. Then I trim engine and tabs up for best speed. Don’t get me wrong, it’s more then manageable. I just can’t firewall-it without thinking like the old boat.

[Rybones]

Gotcha, and that makes perfect sense.