wheres my exact bottom

[wameyer]

OK, I have a Glasstream 2500 eagle. It had a mercury 200 outboard we are trying to make it stern drive and encountered a snag. I did as described from the mercruiser book about finding the keel and doing the 90 degree tool method to find the x dimension. I have what I believe to be 2 keels. If you look at the pictures the first picture is of the back of the transom so you can see how the keel steps up the second is a closer shot and the third is what it looks like on the inside. When I got my x dimension I measured from the long keel and when I found the crankshaft centerline I noticed that the stern drive bracket is 2 inches off and is sitting on the bottom of the second keel. What I need to know is do I measure the long keel or the shorter one that steps up. This is all for the anti-ventilation. I need some help. I hope this makes since if not I can give my number so someone can call me I dont want to have to find an outboard for this thing.

thank you for your time.

 

[oldsub86]

Re: wheres my exact bottom

I am no expert but I think you have to go with the real bottom of the boat. That might not be doable on this hull. One of the problems with making big changes like putting an I/O in place of an outboard. Likely easier and no more expensive to either get another outboard or just swap for a different boat. There does not appear to be any shortage of old I/O's out there these days.

Randy

 

[wameyer]

Re: wheres my exact bottom

Thank you, I was afraid that was going to be the answer, we picked this boat up for a decent price and all the other boats this size are to rich for our pockets, this is a 25 foot boat we spoiled ourselves not to mention the amount that we have into it we need to just finish it so we can get back on the water.

I hope someone else replies, Randy I think your correct though which is making me sick casue now I have to sell the motors and outdrive I have to find another outboard when I sold the one we already had.

 

[daydreamer1252]

Re: wheres my exact bottom

You may want to move or repost this in the restoration, building and hull repair forum....There may be a way to rework or eliminate the step there at the transom and make it suitable for an I/O. The people there are experienced and clever....hope you can make your plans a reality...

 

[wameyer]

Re: wheres my exact bottom

OK will do thank you daydreamer

 

[wameyer]

Re: wheres my exact bottom

Also here is a quick question the book stated for speeds above 50mph increase the x dimension by 2.5 inches. Does that mean raise the outdrive or lower it more into the water?

 

[Bondo]

Re: wheres my exact bottom

Also here is a quick question the book stated for speeds above 50mph increase the x dimension by 2.5 inches. Does that mean raise the outdrive or lower it more into the water?

Ayuh,... Higher, Up, Taller X dimension...

Yer puttin' an outdrive on an outboard hull built with a set-back delta pad, I believe they call it...

Are ya pullin' yer X di from the bottom of the flat transom surface, or from where it would be without the setback pocket,..??

Are there gonna be motor interference issues inside the hull because of how low it sets,..??

 

[wameyer]

Re: wheres my exact bottom

I am pullin my x dimension from the lowest keel if there was not a setback. Right now my bracket that holds the gimble and outdrive to the transom is resting on the setback and will not go lower. I can go higher, if I need to measure from the delta pad then I can go higher for sure without any issues. Should not be any motor clearance issues.

 

[Bondo]

Re: wheres my exact bottom

Ayuh,... How big is the setback, in inches, fore, 'n aft, 'n depth,..??

Alpha drive,..??
Bravo drive,..?? Which 1,..??

 

[wameyer]

Re: wheres my exact bottom

It measures 33w x 4h x 8 1/4 deep the reason I ask about the bravo 1 or alpha is would one make a difference with the set-back deltapad I guess lets take this step by step

 

[oops!]

Re: wheres my exact bottom

no....it wont. the x dimension is still crank shaft center line.

the determining factor for alpha/bravo is the hp of the motor installed........the raw basic rule is 300 hp........sooooo....if you have a 454 or other bbc.....then bravo. but if you have a 4.3 v6 or even a 350 (5.7l) then alpha.

that is a real conundrum you have going.......the step in the hull so close to the transom will cause ventlation problems.......i would use the lowest point of the hull....this could cause you a loss of top end speed......but, if you mount it using the final transom height.....you could end up with the prop moving air !

 

[oops!]

Re: wheres my exact bottom

one other thing.......if the lower x dimension will not give you enough room to mount the outer t plate.......you will have to loose the delta step.....that means glass in a new outer bottom.
you will also need room for the bilge drain. on a flat bottom like that......the drain can be mounter to one side......but its a weird setup.

 

[wameyer]

Re: wheres my exact bottom

When I got my x dimension using the actual keel I am approx. an inch too high. So if I lay it flush with the step up piece it will mount but obviously its too high and I do not ant to sacrifice speed. That step up piece is the monkey wrench in the engine. I am at a dead stand still. I guess the only good thing right now is I still have my gil marine sea drive so if I had to put an outboard back on I could But whatever is best then thats what I will do.

Yea thats what I was afraid of I really do not want to cut the delta step out. The plate is resting on the delta pad step out which puts it about an inch to 2 inches too high

 

[oops!]

Re: wheres my exact bottom

i am confused buddy........

ok.....if the lower keel x dimention gives you room to mount the outer transom plate.......WAHOO !.

if you are worried about the extra drag the lower unit will give you......dont be....the difference is about one mph.

the real problem we have here is not knowing the amount of air that passes under the upper step.....if you mount the drive in the areated area......your prop will cavitate and you aint goin nowhere fast. if you mount it lower.....you will have tons of bite.
and loose very little on the top end.

but one thing.........this is very important.........the degree of the transom has to be 110 degrees......check if your outboard hull has that rake.....if not....you will have to build it up.....and then you are dealing with flatness and parallesim.......a real can of worms.

 

[wameyer]

Re: wheres my exact bottom

The problem I have I cant lower the unit at all because the gimble plate rests on the delta pad. Everything needs to drop about an inch to get my proper x dimension. I know there is rake on my hull how much I do not know.

 

[wameyer]

Re: wheres my exact bottom

I have been looking at ALOT of race boats and they seem to have the same general hull design as what I have. It appears that their x dimension is measured from the deltapad. If thats the case I need to actually raise mine. I know this is another forum but I came across it I hope this isnt against forum rules to post. They seem to call that delta pad a variable deadrise. I hope this can enlighten the experts so they can help enlighten me. I hope this is the case so then I can continue to finish my boat.

 

[oops!]

Re: wheres my exact bottom

you have 1.5- 2 ins of play in the lowest x.

racing machines are 2 ins higher than normal.

this may give you the best of both worlds...

this may also free up any problematic areas with the bottom of the oil pan.
if the pan still hits the bottom of the boat....you may have to go to a different pan or dent (modify) yours.

 

[wameyer]

Re: wheres my exact bottom

OOOPS, are you saying I should just mount my gimble brace right on top of that delta pad to where I am about 1- 1.5 inch above my x dimension, if so then I am good all around and I can get back to work, If I have to lower that brace then I am in a bad situation I will have to find an outboard and remount my seadrive and put an outboard back on.

 

[oops!]

Re: wheres my exact bottom

once again....we dont know the ventelation of the pad......each pad is a different distance from the transomas well as a different height.....that means no solid water....just lots of air bubbles...
going from the lowest point...is the only way to insure solid water contact at speed IMHO.

however....i will ask a few of my building buddies if the are in town....one of them is the builder of the mannerfelt step hull design bat boat...(vector)

 

[wameyer]

Re: wheres my exact bottom

ok, great thank you