TOPIC: moving weight aft G 3

Neat boat

1960 G 3 Glasspar

1960 g 3 center deck

Center deck

The forward cockpit was covered with a canvas and the steering was was moved aft and mounted to the center deck.

Yeah Chris,...I have seen a couple of center deck G-3's rigged like that.

I am curious,....where was that picture taken at?

Mount Dora, FL

That is a 75 engine, right?

Yup, a 75.

Seems like it would be faster on top speed, but hard to get up on plane.

%0 years ago, I would lean forward from the aft cocpit to control my G-3. I was always big, so with my body weight as far back in the boat as I could go, I hoped for more speed.

50 years ago.

Sorry, the board was down yesterday.

I'm having trouble of porposing over 3200- 3500 rpm ..I moved the engine up 1 " and it got worse, took longer to get up on plane. When I had the old 1978 70 hp Merc . it didnt do this Since I put the new Merc. 50 on I'm having this problem Gave it a shot to 4500.. rpm I'm afraid the boat will flip or come crashing down on a wave when its choppy out ,I've been getting this porposing problem I'm going to move the engine back down 1 " it ran better This g3 doesn't like choppy water !!

65G3 wrote:

I'm having trouble of porposing over 3200- 3500 rpm ..I moved the engine up 1 " and it got worse, took longer to get up on plane. When I had the old 1978 70 hp Merc . it didnt do this Since I put the new Merc. 50 on I'm having this problem Gave it a shot to 4500.. rpm I'm afraid the boat will flip or come crashing down on a wave when its choppy out ,I've been getting this porposing problem I'm going to move the engine back down 1 " it ran better This g3 doesn't like choppy water !!

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65G3:

I have a 1960 G-3 with a similar outboard to yours (2009 Mercury 50)
and occasionally the boat will start to propoise at which time I can "adjust" it out with my trim and tilt or by raising or lowering the jackplate. I am wondering if the added weight of your new motor is causing the porpoising?? I have also read that the G-3's will do that if there is an imperfection on the bottom of the boat near the transom. As I recall it is called "hook" or soemthing like that? I am sure the other members will chime in on this for you.

Here is a picture of the set-up on our G-3:

Every prop provides lift. Some are stern lifters, others are bow lifters.

Engine height can make a difference.

Engine trim can make a difference.

Weight and location of gas, gear, and passengers can make a difference.

It is an outboard. One of the nice aspects of an outboard powered boat is to take everything out and off the boat and flip her over. Take a metal 4 foot long level and run it fore and aft on the upside- down bottom and see if there are any lumps, bumps, curves, flips, and other distortions from a "billiard table" smooth and straight boat bottom running/getting on plane running surface.

Thanks for all the help . That's why I love this forum board !! I'm gonna move the engine down 1 " where it was ,the cavitation plate was about 1/2 below the bottom of boat , Then I'm gonna get 2 or 3 -40 lb bags of sand and put them up under the bow and move the gas tank and battery up under the bow too! I know 5 gallons of water weighs 40 lb, so I have 6.5 gallons of gas.. that's gotta weigh about 55 lbs and the battery is about 30 lbs ! I'll figure out whats going on with this. I've been restoring this boat since I got it in 1995 , I can't give up now !!

The cavitation plate of the outboard is below the bottom of the boat?

Water off the bottom running surface of the boat GOES OVER the cav plate when you are running?

65G3 wrote:

Thanks for all the help . That's why I love this forum board !! I'm gonna move the engine down 1 " where it was ,the cavitation plate was about 1/2 below the bottom of boat , Then I'm gonna get 2 or 3 -40 lb bags of sand and put them up under the bow and move the gas tank and battery up under the bow too! I know 5 gallons of water weighs 40 lb, so I have 6.5 gallons of gas.. that's gotta weigh about 55 lbs and the battery is about 30 lbs ! I'll figure out whats going on with this. I've been restoring this boat since I got it in 1995 , I can't give up now !!

Yeah this all sounds wise, LOL, Why not just have a concrete truck dump a load in the bilge:) A bow or hook that will make a difference you should be able to notice looking down the bottom from the bow end if you have a good eye? Mine has a real bad hook and I installed trim tabs, would never remove them even with a pefect hull when I redo it. Rides great and get top speeds plus have the battery in back with 2 1/2gal spare gas plus 2 6gal tanks under the center deck with nothing under the bow except line. Idiots used to put sand bags in the front trunk of Corvairs and Bugs mostly cause they didn't know to run less air pressue in the front tires or just wanted that lowered front look at the sacrifice of ride. My 650 will get on plane as quick or before a skier does, about 8-12mph.
ps. imo bottom of cav plate should be inline with bottom of hull or slightly above to start, never below. As Seabuddy said the prop change might be something to think about to give less bow lift, would need some experts on props for that I'd think?

I found out what was causing the porpoising . !! I moved the engine down 1 notch , cavatation plate is where it should be. I moved the fuel tank under the bow.. Put 2 bags of 40 lb. topsoil bags under the bow too !! That's about 130 lbs !! That made a big difference Took it up to 3200- 3500 rpm where I was having problems So far so good !! Increased speed to 4000 rpm !! No porpoising !! Gave it a shot to 5200 rpm !! Once in a while a wave would start me porpoising a little.. Runs great at 4000 rpm without getting banged around Notice the bags of topsoil were starting to move to the rear.Now I have to put tie down straps up front to hold everything secure !! When we rebuilt the boat .. a lot of more weight was added to the floor, the sides,right where you sit, the old floor was thin and would flex a lot, Transom was brought to 20".. All that added weight ,made a difference in handling !! At least now we can go out for a nice cruise with out getting banged around !!! Oh what the heck.... I added another 40 lbs of weight under the bow for good luck !!!