Glen-L.com

You're coming along nicely. The woodwork itself speaks of perferction!




This is jibberish.

Tilt the motor up and the bow will raise. Tilt motor down and the bow will come down.

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You'd be surprised if you added every extra cost that isn't much in the "big picture".

wow your going all out on your build. looks great.

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RetroMan
Built A Zip/Flying Saucer. I do my boating on South Oyster Bay, Long Island, NY
Documenting my build on YouTube @ http://www.youtube.com/SuperUnknownMC

Hi Wistler, just curious. Yes tilting the engine can and will compensate for weight balance, but isn't it better for the engine to be fully dropped down for maximum speed and power as opposed to tilted up to compensate for less than ideal balance fore/aft. Just looking to learn everything I can here from folks that know a lot more than me. Or is it that regardless of engine tilt as long as your are 'planing' correctly that that is all that really matters.

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This is my first, last and only boat build.

http://www.gdzipbuild.blogspot.com

Ideally, the outboard will be mounted exactly perpendicular to the keel line for maximum performance. In the real world, we have to adjust in or out to compensate for weight placement, deviations in the bottom, and even prop design. This is why we like trim and tilt so much.

It appears to me that the transom on the F/S and Zip are both a little more verticle to the keel line than more modern designs. This would result in the need to place weight forward which is a great solution if the boat is already built. Unless you guys talk me out of it, I will add a couple of degrees to the transom angle on the F/S I'll build next winter. Mine will be stretched to 13' and set up with a single cockpit as far back as I dare. I'm lookin' to go pretty fast with a fresh Mark 55.

Randy

Can't wait to see your build randy...

How high will your cavitation plate be to start?

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Boat building can best be defined as an endless series of
tragedies obscured by the occasional miracle, followed by a good bottle of beer.

Don't Dream Your Life, Live Your Dream

Also, what angle will you set the transom at if not the plan's?

I usually go at about 14 degrees

_________________
Boat building can best be defined as an endless series of
tragedies obscured by the occasional miracle, followed by a good bottle of beer.

Don't Dream Your Life, Live Your Dream

If you are interestsed I have the original owners manual for my Mark 35A. Here's a copy of the engine set up per the Mercury manual.
I will be starting with a 17" height on my transom.

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This is my first, last and only boat build.

http://www.gdzipbuild.blogspot.com

For what it's worth, I mounted my fuel tank foreward in the Malahini. I have a 320lb engine and I figured I needed some weight up front. My original tank was a 19-gal Moeller, but I had some difficulty with my filler hose, so I installed a 12-gal tank. I also have two hatches on my rear deck and I wanted to use that space for storage. I've only been out twice, but the second time, I did get to push her a little and briefly had her up to 40MPH with 4 adults on board. I did not notice any porpoising.

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2011 MALAHINI - KICKED IN THE HEAD

I wake up with a 16ft woody every morning
Video: http://www.youtube.com/watch?v=534DBtp1Cnc
Website: https://sites.google.com/site/2011malahini/

Warren, I also like 14 degrees. I'll place the cav plate dead even with the bottom of the boat (not including the keel). On a couple of designs, I needed all of the 14 degrees to calm the boat down. I'll admit that I tend to load the back of the boat more than most. I'm always trying to reduce the wetted area as much as possible. I have 2 favorite speeds--real fast and real slow.

Randy

I knew a little of your background, that's why I wondered on the angle & height.

I try for even with the bottom or 3/4-1" high on something like my TNT's that I built

I'll throw some cup on the prop if it cavitates

_________________
Boat building can best be defined as an endless series of
tragedies obscured by the occasional miracle, followed by a good bottle of beer.

Don't Dream Your Life, Live Your Dream

Since my kids/grandkids are all 1200 miles away, I'm no longer concerned with pulling water toys. I am prepared to jack the motor up as high as possible. I'll be ready to try Warren's 3/4-1" above the bottom. I expect cavitation coming onto plane. Cupping is something I almost always do when propping out a boat. I look for a prop with low enough pitch to allow the motor to run a few hundred RPM above max recommended engine speed, then cup enough to bring the RPM to the top end of the recommended range with just me and 1/2 tank of gas. Normal load brings top RPM right into the middle of the range.

With small Merc 4 bangers, I go all the way to 6,000 RPM (they are out of revs at this point)then cup back to 5,700-5,800. Normal load (wife, picnic basket) brings the RPM to around 5,500.

I'm also considering an aftermarket TnT unit. I don't like adding the extra 35 lbs to the transom, but the offset might be worth it.

Randy

Engine trim is crucial for performance. Leaving the engine tilted all the way down will pretty much equal putting ballast in the front as the propeller force vector will lift the transom, consequently the bow will go down.
Tilting the engine out (the propeller force vector) will force the transom down and lift the bow. From a stand-still (hole shot) you'd want to tilt the engine in/down to lift the boat out of the water. Once on plane you'd want to tilt the engine out/up to lift the bow from the water and reduce the hull-to-water surface and drag, hence the speed will increase. Less friction is more speed. The same effect is very visible during (sharp) turns where the boat tend to lean into the turn like a bike. It's the propeller force that raise the outside of the transom forcing the inside and bow down.

For example (trimable engine required...) Once on plane with the engine trimmed in you throttle back to 3/4 or so. Trim the engine out and note an rpm and a speed increase (without the use of the throttle). Continue trimming out until the propeller starts cavitating, (you'll note decreasing speed and increased noise) and trim slighty in again. That's pretty much the sweet spot combining performance and fuel consumption.
Dealing with porpoising can be a combination of trimming in and adding weight in the front end.

With a non-powertrim/-tilt engine you'll have to find the tilt posistion that give the best practical overall result. Usually a mediocre hole-shot and a decent running speed.

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You'd be surprised if you added every extra cost that isn't much in the "big picture".

Another thing you can do with your trim control is relieve some of the engine torque you feel in your steering. I have Teleflex NFB, so I don't have that issue, but if the engine's torque pulls in one direction, you can trim the engine up to the sweet spot to ease that pull. That was a huge issue on our pontoon boat. Once trimmed up, I could track in a straight line without even touching the steering wheel. Just remember to trim the engine back down when your are docking or you won't have as much control.

_________________
2011 MALAHINI - KICKED IN THE HEAD

I wake up with a 16ft woody every morning
Video: http://www.youtube.com/watch?v=534DBtp1Cnc
Website: https://sites.google.com/site/2011malahini/