Need ops .81 help

[Ben Ballard]

Hi, guys. New to this scale hydro thing... Came up. With a 82 dumas atlas hull with a ops .81 engine, no prop. What size octura prop should I look for and 2 or 3 blade? Not looking to set records here just get Use use to the boat and not fry the motor. Fellow I got it from told me he ran 50 percent odonell but he wasen't much help with prop numbers. The ops has a red head on it with a slide valve carb if that makes a difference. It does have speedmaster hardware with a 3/16 shaft. Thanks, Ben

 

[Hydro Junkie]

Technically, that's too much motor for that boat. Normally, on a scale hydro with a legal race engine, props range from 55 to 62mm. Using an 81, you will be looking at props between 62 and 70mm to start with but that is an educated guess. Others may be able to give better scoop on your prop more than I

 

[Ben Ballard]

Thanks, Any info will be helpful. So would it be in my best intrest to try and find a .67 or can this setup work? Like i said im not trying to set the world on fire just looking to get use to driving this style of boat.

 

[Buddy Benedict]

67 and 80's look very much alike. They both used the red cooling jacket and the only real way to see if you have a 80 is to check the bore. I don't know what the bore of the 80 is but a 67 is .956. Take the cooling off and remove the head button and check the width(bore) and see if it is .956 for a 67. If it is bigger is a 80 motor.

If you plan on racing the boat, the rules in IMPBA and NAMBA limit you to a 67 motor. As far as props go, with a 67 in it an Octura X457 3 blade would be a good start.

 

[FloridaScaleBoater]

Thanks, Any info will be helpful. So would it be in my best intrest to try and find a .67 or can this setup work? Like i said im not trying to set the world on fire just looking to get use to driving this style of boat.

Could you post a picture of the engine you have?

There is only one difference to the outside of the engine between an 80 and 67

F.Y.I. OPS doesn't make an 81

 

[bermudadude]

theres a bulge in the .80....the cooling fins stick out wider than the water jacket and the rest of the case. the .67 is slim all the way up. tho the piston/sleeves are interchangeable

if its a .67 then yup x455,x457,x460. if its an .80,those heavy hydros wont be hurt, just dont over prop it and it should still turn fine. id say a x460 ,x462, x465-max!!

and didnt they change the rules a few years back increasing the size on scale to allow the use of mac .84's ? which also allowed the k&b .82 and o.s .81

 

[glenng]

Hi, guys. New to this scale hydro thing... Came up. With a 82 dumas atlas hull with a ops .81 engine, no prop. What size octura prop should I look for and 2 or 3 blade? Not looking to set records here just get Use use to the boat and not fry the motor. Fellow I got it from told me he ran 50 percent odonell but he wasen't much help with prop numbers. The ops has a red head on it with a slide valve carb if that makes a difference. It does have speedmaster hardware with a 3/16 shaft. Thanks, Ben

I built one of those in 1983. Try to post pics of the bottom of the sponsons. If the boat was built to plans- the ride pads need to be cut off(sponsons are too deep).. Another weak point was the luan mahogany plywood- very soft and the hardware would loosen up with every run. Try 30% ODonnels and a X457/3 if you're @ low elevation or a X455/3 above2500 ft.

 

[glenng]

theres a bulge in the .80....the cooling fins stick out wider than the water jacket and the rest of the case. the .67 is slim all the way up. tho the piston/sleeves are interchangeable

if its a .67 then yup x455,x457,x460. if its an .80,those heavy hydros wont be hurt, just dont over prop it and it should still turn fine. id say a x460 ,x462, x465-max!!

and didnt they change the rules a few years back increasing the size on scale to allow the use of mac .84's ? which also allowed the k&b .82 and o.s .81

The 1/8 scale class is limited to .67C.I or 11CC

 

[Hydro Junkie]

didnt they change the rules a few years back increasing the size on scale to allow the use of mac .84's ? which also allowed the k&b .82 and o.s .81

No, the size increase was done to make running gas engines doable, unlike the Pro Boat "sorta scale" Bud and later versions of the hull that didn't really work

 

[FloridaScaleBoater]

theres a bulge in the .80....the cooling fins stick out wider than the water jacket and the rest of the case. the .67 is slim all the way up. Correct, what I was hoping to see

tho the piston/sleeves are interchangeable Wasn't aware the P&S were interchangable,, I did know you could put a 67 P&S into the older gold head 65 without issue.

if its a .67 then yup x455,x457,x460. if its an .80,those heavy hydros wont be hurt, just dont over prop it and it should still turn fine. id say a x460 ,x462, x465-max!!

and didnt they change the rules a few years back increasing the size on scale to allow the use of mac .84's ? which also allowed the k&b .82 and o.s .81

NOT TRUE,,,, Scale is limited to 67 (11CC) max as Glenn states

 

[Dasboatman]

Hey Ben,

I say - Run what you have, Unless your planning on entering it in a sanctioned race - then you'll have to go to a smaller displacement engine to be legal - i.e. .67 /11 cc.

The bolt pattern for the OPS 67 / 80 are the same. I don't believe you'll notice a whole heck of a lot of difference between the output power of the OPS 80 compared to the .67. I never did.

The last time I raced OPS 67 in a scale boat was 1999. The best set up was:

• running an OPS 80 slide carb
  
• running 40% nitro, 16 % synthetic with 2% castor oil.
  
• It ran an 11cc MACS muffled marine pipe Stock # 1369 at 12" measured from center of engine bore to the high point of the 1369 pipe.
  
• Deck clearance was .018 in. with rotor at .0025.
  
• I ran an X457 3 bladed prop, in my own hull which weighed 12 1/2 # less fuel.
  
• I needed a 16 ounce tank to start and launch early and finish the race.
  

I would almost guarantee the Atlas weighs more than my hull, so you might want to try an X 455/3 at first.

Shamrock Imports lists the different parts between the OPS 67 and 80 are:

• crankcase
  
• Piston/sleeve
  
• wrist pin
  
• exhaust gasket
  
• head shims
  
• water cooled exhaust and fittings
  
• and the 80 9 mm slide marine car
  

CHEERS !!! Bob

 

[Ray Sametz]

I agree Bob, blast from the past talking about Shamrock!!!!

 

[Ben Ballard]

wow! Thanks guys for all the help! I'm not planning on racing this boat, just playing with it and as I said to get the hang of it. Living in Missouri I haven't found a club to race with if I wanted too. I would love to get a better boat later on as my driving improves. I have a 4 acre lake to. Practice on and I would hate to tare someone else's boat up with my inexperience. Will try and post pics soon. Not to be too greedy for info, but I'm not sure what the stock needle and mix points are either. I can't seem to find any thing about larger ops engines anywhere and I don't want to lean it out too much if the prior owner got screw happy with the settings.

 

[Samuel Hagan JR]

wow! Thanks guys for all the help! I'm not planning on racing this boat, just playing with it and as I said to get the hang of it. Living in Missouri I haven't found a club to race with if I wanted too. I would love to get a better boat later on as my driving improves. I have a 4 acre lake to. Practice on and I would hate to tare someone else's boat up with my inexperience. Will try and post pics soon. Not to be too greedy for info, but I'm not sure what the stock needle and mix points are either. I can't seem to find any thing about larger ops engines anywhere and I don't want to lean it out too much if the prior owner got screw happy with the settings.

There are replacements parts for OPS. There actually improvements. On a gas flow I think they flow at 5. Not sure on a Boris meter.

Run it a couple laps and bring it in and check the plug. The plug will tell you what it's doing.

 

[Dasboatman]

OK, Ben. Run it and have fun.

Make sure you buy "Boat Fuel" for it. It has a lot more lubrication that the airplane fuel in most LHS. I'd suggest flushing the engine with WD 40 after a days running, and then pickle it with a good oil post run. I used 3 in One oil for years, I now use Corrosion X (red can) or automatic transmission fluid.

I doubt he has a Boris Flow meter, Samuel.

Needle valve settings are pretty much different for each engine/setup. I'd suggest making sure you have a mark on the needle valve housing so you can count the number of rotations it is open right now by counting the revolutions to close the needle valve, then back it out that amount again and add another 1 turn or so to make sure your rich. Maybe start about 5 turns open and see if it will start there. It should be plenty rich there. When I find the OPS engines I have here somewhere, I'll see where the needle valve setting is on the last 80 slide carb I ran.

Hey Ray,

The Shamrock Imports parts listing was set up very well and easy to read. Tower made it more difficult than it had to be. Most parts I bought from them still had Bob's Shamrock stickers on them. Who did the OPS import go to next?? Remy at Aeromarine?? Lots of water over sponson bottoms to get back there my Friend. Har, Har !!! CHEERS !!! Bob

 

[Ray Sametz]

Bob, yup went Remy, actually sold the line on Tower for a while. Stopped when he was losing money!!!!!!

 

[Ben Ballard]

Ha,ha,ha! Yeah, no flow meter Mr. Samuel and not real sure what that is...yet. But once again thank you ALL for the help! Don't want to make this a long post but let me give you all some background being I'm a new member. I am 37, been around all types or racing from the time I was able to walk, rc boats excluded, I currently race dirt late models on a weekly basis on Saturday nights here local so I am a bit mechanically inclined. This whole rc boat thing started at the beginning of summer when dad bought a tunnel hull outboard job cause "he always wanted one since I was a kid" . We have had more fun with that thing than should be allowed by law! Now we have a hydro and are a bit wet behind the ears with it! Lol! Coming from a racing background I do know that good info is money saved and I do thank you all for your help. Working on getting pics up now if computer will work with me. Again, thank. You all!

 

[Samuel Hagan JR]

If you ever need parts www.gotnitro.com has is the North American OPS dealer. I think?