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hucks fin
12-16-2001, 10:58 AM
I have a 1973 18.5 ft true flat bottom hondo. My question is were should I place the motor? I currently have it 36 inches from the transom. Right now its seems the bottoms dragging in the water but, when I lift the plate it wants to hop. Any tricks to find the right balance or is this accurate?

Thunderbutt
12-16-2001, 02:51 PM
Good luck finding out about your motor placement. I've asked that question so many time and no answers. I have the motor out of my 1972 Spectra for a check up and want to put the motor back in the right place to keep it from porpoising at high speed. Originally posted by hucks fin:
I have a 1973 18.5 ft true flat bottom hondo. My question is were should I place the motor? I currently have it 36 inches from the transom. Right now its seems the bottoms dragging in the water but, when I lift the plate it wants to hop. Any tricks to find the right balance or is this accurate?

pgf127rt
12-16-2001, 04:49 PM
Hucksfin, basically all flats are different, therefore the only way to find the true measurement on your boat is thru trial and error, moving the motor in small increments and running it till you find the happy medium, also the position of the prop under the boat to the plate is very critical, if you can find someone in your area who has setup a flat similar to yours, maybe they can give you some baselines to help narrow the ideal setup dimensions, but there are several factors like weight placement of battery fuel tanks,etc. that can affect your dimensions, sorry I can't offer a quick fix.

Infomaniac
12-16-2001, 08:27 PM
HF 36 is a bit fwd. But as explained each boat is different. How far away from the strut is the prop? Moving the prop fwd is the same as moving the engine back. Think of the prop as the pivot point of the boat.
Raising the plates and the boat bounces means you have reached the limit of where the boat will carry the nose.
Choices: trial and error as explained.
Move the engine
Move the prop
Prop with more rake
More HP
There are some very basic set up measurements that I will try and dig up.
Transom to v-drive
Transom to engine
end of plates to prop.
[This message has been edited by Infomaniac (edited December 16, 2001).]

hucks fin
12-16-2001, 09:00 PM
Infomaniac- Thanks for the info!
I broke my outdrive shaft and a buddy of mine gave me a replacement. Not thinking I replaced without checking the length. After reading your reply I checked it. The prop was a inch and three-eighths out from the strut, it was previously at a quarter, it makes sense now! Basic set up measurements would be great. Thanks http://free.***boat.net/ubb/biggrin.gif
[This message has been edited by hucks fin (edited December 16, 2001).]

pgf127rt
12-17-2001, 05:48 AM
Hucksfin, On our raceboats we are allowed a maximum of 3/8" prop to strut, the reason for that is to minimize the whip effect, which could cause shaft failure and losing a prop at speed, which is very detrimental to your health. Infomaniac is correct on a flat that starts porpoising on the big end is due to a lack of power required to carry the nose, however the 1" extra on the shaft will also roll the nose over at speed, been there done that not a lot of fun.

058
12-17-2001, 10:52 AM
I just checked the engine placement of my Hondo and it measures 36" transom to ft. of engine and 61" from transom to bell hsg. face so I don't think engine placement is your ride problem unless you are running an unusually heavy engine, V12 R/R Merlin maybe? Check the plate adjustment before making any major changes to the boat/engine and prop to strut clearance. As pgf127 said "No more than 3/8" More than that the prop is mostly supported by the shaft and may whip. Also need to know where the V-drive is mounted, [how far from the transom?] Hondo also made a "ski-flat" with the V-drive moved back for more seating room and increased the propshaft angle. Perhaps you have one of these hulls.

superdave013
12-17-2001, 12:05 PM
I wouldn't change anything other than get the prop in the right location. Then take it out of a spin and go from there.

Fired Up
12-17-2001, 02:11 PM
PGF127,
This is my second attempt. Don't know where my first reply went. How are you doing JDL. What does it mean when you "roll the nose over" on your boat? Do mean actually flipping or specific boat behavior? Did I mention that the shaft in my boat was bent. The prop was 1/2" behind the strut. There were four nickels between the propshaft and the outshaft of the v-drive. This is where the shaft was twisted along the keyway. The key was also twisted. Already ordered another propshaft from Wayne Mettler. I suspect the vibration from the bent shaft (which I could not feel) is what made the shaft seal leak and probably ruined the strut bushing making it hard to remove the shaft.

pgf127rt
12-17-2001, 03:26 PM
Fired Up and HucksFin, when we say the boat noses over, it literally comes off the prop at speed and sticks the nose in the water, My Cole was doing that whem we were testing in preseason, as Wardance say's Many Moons Ago, and it didn't give any indication of what was to come,so, I found myself about as far as my arms would stretch out over the deck and trying to claw my way back into the seat, I made it and the solution was very simple 1 nickel off the shaft and she carried the nose until I sold it, the problem with flatbottoms is to test them you have to run just like you were racing and be ready for anything to happen, I am sure SuperDave has some stories about tuning the handling of a flat. it is not rocket science.

howard69
12-17-2001, 03:56 PM
In ***boat this month they talk about adjusting the plate in a v like configuration,what does this do to help get the hop out

pgf127rt
12-17-2001, 07:19 PM
hf,I don't really have a clue, but in thinking about a true flat a v configuration could help by releasing the trapped air out the sides of the plate, sorta like a runnerbottom releases the air out of the traps on the outer plates, but that is just my theory, maybe some of the guys who have ran the true flats can enlighten us. I have driven all kinds of flats, but the true flats were already setup, so my experience with the plate is minimal as far as different ways to limit the boink.

Fired Up
12-17-2001, 07:20 PM
I've heard of using the nickel trick to add length to the shaft. Why are coins, which are inherently a soft metal used? The ones I pulled out of mine were all mushroomed. Hasn't anyone made hard metal spacers instead?

Fired Up
12-17-2001, 07:23 PM
There goes another term.....BOINK. I've seen it and heard it. What are you referring to? What does a boat do when it boinks? Sorry about all the ignorant questions. Just starving for good info.

PGF545
12-17-2001, 08:30 PM
I have been trying to remember our settings on the old pure flats, and I can't remember right now, but we used to run our motors a lot farther back in the flats as to what we run in the runner bottoms. I would say that the motor is too far forward. I would start moving it back until it didn't hop anymore. The runnerbottoms have more rocker in them allowing them to ride differently than the old flats. If I get anymore information I will post it.

pgf127rt
12-18-2001, 03:24 AM
Fired up , Boink is what the boat says when it hops due to not taking a proper set, commonly called porpoising, but to the driver it feels more like a boink, the nickel is used for gauging the length of the propshaft, thickness is about 100,000th. of an inch, evidently your shaft was moving inside the collar, if your nickels were mushroomed, probably causing the twisting that you experienced, on a good tight setup the nikels are not damaged when you retrive them.

Costello
12-18-2001, 07:42 PM
I'm with Bernie (545), 36" still sounds like it's too far forward. Mettler told me that on his open BAF runner bottom they had the motor at 28"!!! That may be a little racey and extreme, but even 34" should make a difference in helping to carry the nose. I agree also with Dave that you have to get the prop in a happy spot. Make one change at a time and do it in small increments, that way you can monitor and track progression or digression of performance and handling. Good Luck. Now for all of the Daycruiser guys...... The prop is way too far off of the strut on my 21'er for my tastes. I've never gotten to drive the boat yet, so I don't know how it handles. Hang Fin says his is the same but handles fine. Are most of yours set up the same way, like 2" off the strut?? Knowing how close we run them to the strut on the race boat and the reason why, this setup makes me a little nervous. Thanks for any feedback.

pgf127rt
12-19-2001, 04:50 PM
Cos, good to see you bouncing aruond in here, want to wish you and yours a Merry Christmas, and a Happy New Year, friom the Lewis', and I agree with Hang on the recrearional v-drive you can probably get by with the extra hangover, because you are not turning the extreme rpms as a Pro Gasser, or are you?

superdave013
12-19-2001, 05:38 PM
Originally posted by Costello:
I'm with Bernie (545), 36" still sounds like it's too far forward. Mettler told me that on his open BAF runner bottom they had the motor at 28"!!! That may be a little racey and extreme, but even 34" should make a difference in helping to carry the nose. I agree also with Dave that you have to get the prop in a happy spot. Make one change at a time and do it in small increments, that way you can monitor and track progression or digression of performance and handling. Good Luck. Now for all of the Daycruiser guys...... The prop is way too far off of the strut on my 21'er for my tastes. I've never gotten to drive the boat yet, so I don't know how it handles. Hang Fin says his is the same but handles fine. Are most of yours set up the same way, like 2" off the strut?? Knowing how close we run them to the strut on the race boat and the reason why, this setup makes me a little nervous. Thanks for any feedback.
My prop is about 1/4 from the strut on my schiada. Seem like yours is pretty far back to me. I would be a little nervous also.
Hang Fin runs his like that? He should know better!

boatguy222
12-19-2001, 06:30 PM
costello,
Do you know what prop was on there before?
2" is a ton! I would say 3/8s to 1/2 inch would be "normal" But you might try it first, maybe there is a reason for it.
Marc

Bluefin
12-19-2001, 09:24 PM
Hey Huck's Fin, I'll give you the specs on my 70 Hondo Flattie. When I first got the boat it had the "Ski" setup. Motor sat 23" from transom, with Back to back seats. I put in 2 fiber glass buckets and moved the motor forward 8 1/2". The motor sits about 33" from the transom. All this made no difference in the porpoising. Even after the motor was rebuilt gaining 1000 rpm, my top speed has only went up by 3.5 mph. 78.5 GPS in 2001. The strut is at 9 degrees, and the prop is about 24" from the end of the cav. plate. I am starting to believe that I just do not have the HP to keep the bow up constantly, hence porpoising. Read Jim Wilkes page from ***boat this month, the first article is mine. I was told by Tom Bentley of Menkins that the distance from Cav. plate to strut should be 27". From what Wilkes said I could put on a longer cav. plate (3" longer), in escence this moves the strut forward providing better leverage to keep the bow up. (No more Porpoising) What do you think?

Costello
12-23-2001, 10:34 AM
Dave and Marc, I still think it is back a little far from the strut myself. I bought this boat with no prop. Hang and I discussed it the other day and in reality when I install the prop I got from Marc I will probably be 1 inch back of the strut, give or take. Tony also brought up the fact as did Joe Don that #1, It's not going to make a ton of beans (550 hp), #2, the 3 blade won't cavitate the prop/driveline like the 2 blade on the drag boat. I just want to drive the boat where it is before I change it. If it wants to get up and dance where it's at, I surely don't need to make it any more racey. If it's a turd where it's at, I'll move the prop under the boat further. Thanks for the input and PGF127rt, Merry Christmas to you and everyone else here at the forums.