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HIGH LIFE
02-03-2010, 06:31 PM
have a 16 DONZI O/B, motor is a 200 Mariner 20", thinking of installing a jack plate. Anyone recommend a set-back ? Most likely go with a manual. "HIGH LIFE"

maddad
02-03-2010, 07:25 PM
I can't recomend this because I didn't run it yet, but its 8" back and 5" up. It's there because it's in proportion to good setups on other 24 degree hulls I've seen. A 21' superboat, 16' superboat and a 16' donzi outboard that was in closer and not as high.

mrfixxall
02-03-2010, 07:30 PM
just remember the further you go back the stronger the transm needs to be..

Greg Guimond
02-04-2010, 12:06 AM
HIGH LIFE, what lower unit do you have on the 200?

maddad
02-04-2010, 06:44 AM
just remember the further you go back the stronger the transm needs to be..
This boat has stainless rods from the transom to the stringers.

fegettes
02-04-2010, 06:56 AM
This boat has stainless rods from the transom to the stringers.

I did the same thing, or similar, to this on my 18' Youngblood. I used stainless turn buckles so I would always be able to snug the tension if needed. This is an excellent reinforcement to the transom.

MOP
02-04-2010, 07:47 AM
May find some interesting points here!

http://forums.screamandfly.com/forums/showthread.php?t=158536

Greg Guimond
02-04-2010, 03:38 PM
Throw a set of these in and you can use as much setback as you care to experiment with .........

fasttrucker
02-05-2010, 11:00 AM
My jackplate is not a set back.I have the transom reinforced but getting a stress crack.I was told by a fiberglass shop that this is minor and just the stress from flexing.The way they put in the new transom.Glassed in the top deck doesnt allow it to flex correctly.

rchevelle71
02-05-2010, 02:25 PM
My jackplate is not a set back.I have the transom reinforced but getting a stress crack.I was told by a fiberglass shop that this is minor and just the stress from flexing.The way they put in the new transom.Glassed in the top deck doesnt allow it to flex correctly.

not sure I buy that, if mine was doing that, they would be fixing it, and i would be doing knees, or rods as above before running it again.

dwiggl
02-05-2010, 03:04 PM
Something is really moving to see gel coat pop off like that. Needs to be stiffer.....

MOP
02-05-2010, 03:54 PM
My jackplate is not a set back.I have the transom reinforced but getting a stress crack.I was told by a fiberglass shop that this is minor and just the stress from flexing.The way they put in the new transom.Glassed in the top deck doesnt allow it to flex correctly.

I have seen this type of damage before, and have redone others work! The reinforcing plate is transferring the stress outward, without the plate the transom its self would flex and start cracking at the top all the way across. The only cure is rods with outer backer plates or very substantial knees, knees do not need to be big wide chunks, some of the strongest knees are built over 1/4" plywood ending up 3/4" thick. Most of the force exerted on the knees is PULL, the plywood is nothing more the something to glass to and hold the glass shape while it cures. The most important aspect is the anchoring to the hull and transom, the layup on the transom must be quite a bit larger area wise then many realize, IMO the best layup continues from one knee attachment point across to the other so the engine mounting bolts through it and at a minimum thickness of 1/4". There are a lot of slock shops, how many will do it where you will go through many season with no visible signs of cracking. Rods are the easy way!

fasttrucker
02-06-2010, 09:07 AM
not sure I buy that, if mine was doing that, they would be fixing it, and i would be doing knees, or rods as above before running it again.
Yes,this donzi needs work.It would make for a nice and fun project for someone here on this site.Iam too bizzy working over 70 hours a week.Iam asking here and now for anyone reading this post to consider taking this off my hands.Go for it!This 200hp johnson rocks and is completely restored.The trailer is completely rebilt everything new.I got 62.5 gps and it has more in it with the right pitch prop.Ive been asking $6500.Ive got $8800 in it.Will consider all offers......

Greg Guimond
02-06-2010, 10:52 AM
Run the knees right up to the lip .........nothing stronger :wink:

HIGH LIFE
02-06-2010, 06:12 PM
Greg G , After looking at your pictures, do the knees extend thru the deck area to the stringers ? Before installing my motor I made up a 1/4" SS plate that goes down the inside 4" over the top 2" and down 16" plus 16" wide. P.S. if the knees go to the stringers how do you take the deck off ? "HIGH LIFE"

HIGH LIFE
02-06-2010, 06:34 PM
MOP, I understand the forces involved w/ moving the motor off the transom. I would like to buy a jackplate and would like info on the set-back. Presently running a 20" w/standard l/u for a '93 Mariner 200. Realizing that app. 170 hulls were built, how many owners would like to work on maximizing their hull speeds, might not have much info to gather. "HIGH LIFE"

Dave911
01-09-2017, 01:36 AM
Sorry for the resurrection and hi-jacking, but I've secured a 1976 Donzi 16 OB with a Merc Black Max (~220hp with upgraded carbs), and I need to weigh the need and options for securing the transom. My kids'll be on this boat, close off the coast of CA on nice days, so I don't wanna test my luck.

#1. Ya think $1,500 will cover having SS rods installed from the transom plate to the stringers??
#2. How about expenses for knee braces? Maybe $2-3K??
#3. Is the backing plate stock from the factory on all 16 OBs? Or is the plate a sign of a band-aid job that's already been done?

Pics below. Thanks for any insights.

OH, and please disregard the windsheild. It looks functional, but ruins the boats lines. Must go!
Dave911


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Morgan's Cloud
01-09-2017, 06:27 AM
Judging from the pics (which are worth a thousand words) I'd completely re-do the transom from scratch . The idea of s/s rods would just be a band aid IMO

Bear in mind that a 225 Merc is not only much heavier than what the max recommended HP was for that boat back when it was built but it's also a minimum of 100hp more than factory recommended also. Could be more even as the OBs back then were crankshaft rated and the newer ones are supposed to be PSHP rated .

Dave911
01-10-2017, 04:17 PM
Thanks, Morgan'sCloud. I just visited the boat, and put all of my 200lbs on the tilted motor and gave a good few bounces. ZERO movement. Plastic hammered all over the transom with consitant sound qualities. I'm gonna bring in to an hull guy shortly. But thanks.

dwiggl
01-11-2017, 02:55 PM
Dave,
Your are about 200; mota is about 375 lbs. Thats befor the force of 225hp & a propellor levering against the top of the transom. Something is moving to cause cracks. If you want to see it, have the wife drag the boat down the highway while you drive next to the transom. I bet you will see movement. I did the band aid of rods on a low profile outboard with a 115 for about 5 years until the transom was shot. It worked but was a band aid. And that boat was lighter that a sacred Donz. (Now I run a 200 and the Trans. is solid) The kness are real trick and work great, and you do need a whole new transom when you can cough the dough to get it done. Love the boat. Contrary to many opinions the windsheild don't look half bad either!
Do you ever get on the Calif Delta? Will look for ya.

Greg Guimond
01-11-2017, 04:51 PM
...........................

Dave911
01-11-2017, 05:06 PM
Thanks GG. I actually backed out of the deal. I couldn't find a way to fit it in my little garage which is 18' 6". Even with the trailer cut back to the "Y", and the boat at an angle, and backward. Just no fit. Soo...If it's no gonna fit in the garage, I'll hold off on a purchase for something a lil bigger. Best, Dave...I hear there are a couple people lined up behind me to buy, but I can share the owners contact info if anyone wants. PM me.