motor setup 16 o/b

[brett h]

I just bought a '72 16 o/b with what looks like
a late eighties 200hp merc and s/s prop with a
manual jack plate. My problem with the boat is that I get no bow lift even trimmed up and the boat is hard to turn when running at anything past basically idle? Does this sound like an
incorrect motor height problem or wrong prop
or what??? I've got a classic 18 that is running
with 23" plus mirage that I've got more than enough bow lift-maybe the 16 is meant to ride differently than the 18"? Any help would be greatly appreciated.

[MOP]

There is a 16 out by me with a 175 Johnson it runs with good bow lift, his cav plate is about 2 inches up from the bottom. Could be prop type or maybe a hook in the bottom.

[John Benkoczy]

Brett - I'm running a '72 OB with a 1997 175 HP Johnson with a 21 prop - bow lift is not a problem. With the the power trim and (Lenco) tabs, i can always trim out - what prop are you using?

[MOP]

John curious have you GPSed yours to see how fast are you going?

[John Benkoczy]

GPS = 54 mph/5600 rpm @ WOT with the old 17 pitch - haven't GPSed the new prop yet

[Fish boy]

Hi brett,
Great boat. My family's first donzi was a 16 back in the early 70's. It was a calendar boat that parents fenagled a deal on.

http://www.donzi.net/photos/jstaples91.jpg

I am not aware necessarliy of the bow lift problem in your model, but have some outboard experience and suggest the follwing:

1. Look for unusual weight in the bow. Are you storing stuff up there, is your gas tank for some reason there, are you holding water in the front section of your boat?

2. Try a different prop. Turbo gives great bowlift and low aeration at speed. I have heard good things about tempest+, revolution as well but have not tried them. Mirage is the standard and a good prop, but IMHO not the best choice.

3. Try adjusting the engine position (up/down with the jack plate). Worst case scenario, you might need to buy a setback plate to place between your jackplate and the transome. they come in several sizes up to around 12" from the hull. by moving the weight of the engine farther back on the boat, you move the CG thereby giving the bow a built in positive attitude. You also get the prop back in cleaner water which usually increases performance to a point. Unfortunatly, too far, and your boat my start to porpoise.

I would definately try the first two options until exhausted. I was ready to buy a setback plate for my CC when I found a prop that gave me enough lift. BTW, what speed WOT, rpms, prop size?

[Fish boy]

Brett,
2 more things:

1. Welcome to the Donzi Registry.

2. Here is a thread I started several months ago when dealing with similar issues. there are pics of my engine (which was too low) and also some pics from Nathan (jamesbon) showing where he runs his engine.

http://www.donzi.net/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=1;t=006115#000004

As a result of the help I got here, I now run my engine about 2 1/2 inches above where it was in the picture. a little higher when trying to squeak a little more speed out of it.

email me if you have any other questions. I have some friends around here that are a lot smarter with OB's than I am.

fish

[mattyboy]

brett,
welcome to the boards
fishboy as given you some very good points to look at. I have run with John B's ob 16 it not only looks good, but it runs very well I have to push my 16 real hard to keep up.
which brings me to my point.
If you look at John's boat and my boat at the dock it looks like my boat is sinking by the stern I would guess his boat is about 500lbs lighter then my 16 with a 351 and a volvo and all the old hardware ( 700 lbs lighter if i'm in my boat :rolleyes: my beer belly is more mature :p ). He has about 5 more inches of freeboard. So I think you will find it is a weight issue that can be adjusted by ballast and prop and engine trim.
try some easy cog tests get some beer bellies and have them sit in the back, side , front to see if that helps or hurts ride or handling.
the cog on a ob 16 is different than a sterndrive
so you have to find your balance point


good luck

Matty