MRP Hydro hop-up

[decoy706]

Looking for the hop-up kit #10-0950 that changes the gear ratio to a 1.93 to 1 so I can run the X435 prop. Consists of two 32 th and 1 60 th with mounting flange and bearing. this is for the old Hydro twins-or does anyone know of somebody who makes this kit

[n.h.schmidt]

Hi Decoy
I have some experience with the Mrp Hydros. Wich one do you have?. You may have a impossible time in getting that special gear set. That being said I can direct you to something else. Hughey Boats has gears that will bolt right on. Here is what I know has worked in the past. The largest center gear that will fit is a 37 tooth ( 32 pitch).Any lareger and the gear hits the boat bottom. I know that the motor pinion gears of 24 tooth will allow the motors to bolt right on. this gives a ratio on 1.54 to 1. Could be the 20 tooth would also fit .That would be a ratio of 1.85 to one. Ballbearing are easy to get for this gearbox too. If you are interisted in all this and more just let me know here. n.h.schmidt

[Andrewg]

Ned with a 1.85:1 ratio you coud swing some good 40 mm high pitch props and still get good run times even with fairly hot modifieds

[n.h.schmidt]

You are right Andrew. These old boats are not as obsolete as many think. They just need a little rethinking. You need to get away from the small dia prop spinning real fast. Going to larger dia props say 40mm to 45mm is much more efficent in this size boat. Higher gearing is a good way to get it too. I put a special made 700 motor mount in mine. I now use a new type 8.4 700 in my Mr pringles. I can swing a K45 prop on 12 cells. 30 -31mph with 7+ min runs . Good long lasting setup. The geared twin motors should be just as fast or better if done right. I would use series wired 17 turn motors 1.85 to 1 gears to get a long running and long lasting motor setup . n.h.schmidt

[decoy706]

Well guys this is my plan. I want to use a 937 3 blade with the better gear ratio but which one the 1:54 or the 1:85. I have 3 of these monsters in the box yet and a Bud and Pringles I run and need to make one a "cheater" boat with Pro Boat ESC- 3300cells and the new gearing.What do you think?

[n.h.schmidt]

Isn't the 937 -3 a real hi pitch prop. If its the one i'm thinking of don't use it. Wrong prop for this kind of boat. You would be much better off with a X440 -3 a X642 or a x442. For a Graupner CF prop a k42 or k45about $5 ea. The pro boat esc is limited to 10 cells max .You really need 12 cells to do this boat right. You also need to move the cells to the front as far as possible .Take the foam blocks out and put the cells there. get weight off the rear. n.h.schmidt

[Andrewg]

If you plan to use 2 X 12/3 modifieds then use the 1.85. If you use 15-17turn motors use the 1.54 ratio if you run 6 cells to each motor or run the motors and cells in series.

Ned is spot on with the props.

[decoy706]

Guys
I have the .125 drive so the props chace is this 1630/X435/X632/1732/X535
stock was X432
now what choice would you start with

[Andrewg]

X440 -3 a X642 or a x442.

[decoy706]

All those are 3/16 drive which I don't have-now what?Oh and yes the prop has to stay under the hull

[Andrewg]

ok so the original is a 1/8th shaft

simple fix is to use K&S brass tube with 1/8"' ID and 3/16 outer - you may need two tube sizes to do that.

the bgger props should fit and should throw the rooster behind the hull rather than onto it

[n.h.schmidt]

Andrew is right . It's fairly easy to adapt up to 3/16" . Any props you use must be well ballanced .It's a very good idea at all times to do this. With a 1/8" shaft using larger metal props , it could vibrate a lot unless they are ballanced. I currently run my Mr Pringles using a 1/8" shaft and 3/16" props. I also have a 1/8" shaft with a 4mm thread on it to allow me to use all of the Graupner CF props too. The CF props have one real advantage when using a 1/8" shaft. They are very light and do not cause much vibration. As to the prop staying under the hull ,why is that? Thats news to me.

[decoy706]

Where we race if the prop is extended pass the end of the hull it is considered an outrigger which of course we all know run like Hell so the hydro has no chance. Was checking Fuller electrics for hardware when I found this out

[n.h.schmidt]

You must run at the only place in the country that has that rule.Where are you? Nobody else anywhere has that. You can't even surface drive with that rule. The stock Mrp boats extend the prop at least a little behind the transom. Is a mono with the prop behind the transom a rigger too?

[decoy706]

A little is all right but can't be like a surface drive. Yeh I know it S__KS but it's their rules. In the mono if you surface drive it and it did not come that way from the factory you have to race in the Offshore class. Want to know the bad part the MRP Bud Cat has to run in Offshore if you put the dual motor set-up in it. This is why next year I'm coming out west with my fleet of hydros to run.BTW it's Mich former home of hydropoop(only my way) racing. Will be attending the rules meeting for sure this year