Engine upgrade

[abx131]

Its been a while since I last regularly visited. My Miss Bud ran into my neighbors dock a little over a year ago and has been shelved since. I have recently been repairing it and want to do an engine upgrade. The hull is a little heavier in the tail than normal because I fused the top rim of a tupperware container to the radiobox to waterproof it. I know the .18 is a direct swap but I remember someone doing an OS .21. Does any one have any info on this? How it was done or the performance stats on it with that big of a motor? Has anyone else done anything insane with these boats? After Seafair I have been itchin' to get it back out on the water.

[CFRACR]

Its been a while since I last regularly visited. My Miss Bud ran into my neighbors dock a little over a year ago and has been shelved since. I have recently been repairing it and want to do an engine upgrade. The hull is a little heavier in the tail than normal because I fused the top rim of a tupperware container to the radiobox to waterproof it. I know the .18 is a direct swap but I remember someone doing an OS .21. Does any one have any info on this? How it was done or the performance stats on it with that big of a motor? Has anyone else done anything insane with these boats? After Seafair I have been itchin' to get it back out on the water.


I feel that a .15 quality racing engine would be better in the long run. I have read about some with the .21, but lots of mods to acomplish this. Over powered & may not be worth the trouble.

[Hydro Junkie]

I wouldn't do a .21 in the Bud. The lightly layed up hull would need to be re-enforced to make it able to handle the stress. BTW, what ever happened to your 1/8th scale project?

[Watercadet]

http://hobbypeople.net/gallery/146002.asp
This is the motor I used. It is dirt cheep and a direct bolt in with an Associated NTC3 header. There are not too many great .15's out there due to their not being legal race motors. The ones that are are based on a bigger block and not drop in. I opened up the scoop on my Miss Bud for more air to the buggy head and it ran fine.

[engineman351]

To go 'big block' you are looking at doing major mods to get a motor mount in place. Overall the Bud hulls are pretty thin 'glass and I'm sure you would wind up chasing stress cracks. I think the recommendations to use an .18 makes the best sense. I have seen a Bud with an OS .18 side exhaust 'air' cooled car motor run and it definitely was faster than the Dynamite. The owner was afraid to run the boat with the rear wing. Costs about $140 and uses the stock Bud exhaust. The XTM mentioned would be very cost effective. Also, you should consider the K&B watercooled .18. It's over one horsepower for about $80. Being watercooled it has more potential to be modded and responsive to higher nitro content. Lastly, Traxxas 2.5's (.15 cuin) & the new 3.3 (about .19 cuin) put out great horsepower but would require some fab work to get an exhaust mounted. I think Traxxas has released a 2.5 in marine trim. Their engine cost $150-$179...may on the 'Bay a little less. Good luck. RC

[abx131]

Sorry guys I was out of town in San Diego for a week. I am now shopping for a decent .18 to bolt in to my Miss Crud. Hydrojunkie as far as my own 1/8 boat project, I have not gotten to it lately. It is in pieces and progressing slowly. One day it will be done but it may be a while. Thanks for all your input.

[NitroEd]

Does anyone know what the HP rating is on the Dynamite .15, vs other .15's? OS makes a .15 that is .6hp. Is that the same as the Dynamite?The K&B .18 is rated at 1.5-1.6hp, what is the OS?

[Blackmanba]

Hi NitroEd, OS Max .15 CV-MX has 0.6hp at 22,000rpm.

[backwoods]

Its been a while since I last regularly visited. My Miss Bud ran into my neighbors dock a little over a year ago and has been shelved since. I have recently been repairing it and want to do an engine upgrade. The hull is a little heavier in the tail than normal because I fused the top rim of a tupperware container to the radiobox to waterproof it. I know the .18 is a direct swap but I remember someone doing an OS .21. Does any one have any info on this? How it was done or the performance stats on it with that big of a motor? Has anyone else done anything insane with these boats? After Seafair I have been itchin' to get it back out on the water.

It may sound crazy but I bought a OS .21 today for $160. It should be here by Monday and I'll keep you posted on the install and results. I tried everything with the Dynamite .15 to get controllable speed from my Miss Bud. I plan to bed the engine compartment and place a custom motor mount for a firm base. I'll keep pics as I go along to post.

[NitroEd]

Please keep us updated.

[Old Sloppy]

Please keep us updated.

I want to hear more about this one.

Any update yet ?

Harry S. :)

[backwoods]

I want to hear more about this one.

Any update yet ?

Harry S. :)
The shop should call by tomorrow to say the .21 has arrived. Promise to keep posts and pics. Good or Bad we will find out how it goes. All advice is welcomed.

[backwoods]

Alright guys, I have it in my hands. All 1.7HP of an OS MAX.21RG-MX. Cant work tonight. but will design and cut new motor mounts tomorrow night. Made pics of the teardown last night and will post for advice. HydroJunkie, I know you are waiting to say "I told you so!"

[Hydro Junkie]

Actually, I'm not. I like to see the things people do to their boats work out. Just be sure you add another layer or two of glass around the engine mounts to help with the stress cracking problem. You also need to rebalance the boat or it will spend more time trying to reach the clouds than it will reaching for the horizon

[backwoods]

Thanks HJ, your tips and those from others got this boat from stock 24MPH to 36MPH. I will make some pics tonight and have a couple specific questions about the motor placement and those mounts.

[backwoods]

Hey, I need a pipe for the .12. Should I use the tuned pipe from my Dynamite .15 until we see how things go or should I start out with the correct pipe? How about the NovaRossi .21 pipe from Speedmaster? Any advice?

[backwoods]

My dyslexia is showing. I meant "I need a pipe for the .21".

[backwoods]

Alright guys, I had a setback that I couldnt turn down, free labor for another project. Bought a hot tub a week ago and found a way to get it on the back deck. Why do other projects always come to fruition once an RC project gets underway? I am trying to attach pics and get "file too large" any ideas? :confused:

[backwoods]

Here's an update on the .21. I'll try to attach mock up pics. The motor mounts have been designed and machined but not tapped. I need to secure my batteries up front and tie down the new fuel tank. All is looking good. I may crank this weekend and begin break-in. I plan on begining with a Octura X437/3 prop to break the .21 in. I have an Octura Y535 and the plastic Y534. Any suggestions or comments about the 437 are needed! I bought the NovaRossi .21 tuned pipe. I plan on making or modifying a brace to support the pipe. The normal curviture of the header pipe does not keep the tuned pipe under the stock cowling. I want to keep as much of the stock cowling as possible to keep water out of the .21. Any ideas on customizing the curviture to swing in behind the engine and straight out the back? I also will try to order a new antenna grommet to pass the wire up through the body on the opposite side to avoid the heat from the pipe.Not totally necessary at this point but an order item. Any criticism, advice, or comments are welcomed here?? Can't attach a photo. My smallest photo is 408KB limit is near 102KB. Any ideas there?

[BoatDoc]

for your photos...open them with microsoft paint, then go to the drop down menus and find "stretch/skew" (under tools, i believe). i just downsize them in there, be sure to use the same value for horizontal and vertical. after you downsize it, save the file (i go to "save as" and rename it so i can preserve the original). after saving go to "tools" and check the attributes. it'll tell you the size of the file. once they are below the kb limit then you can post 'em.

[backwoods]

Here's a try.

[backwoods]

And here's the custom mounts.

[backwoods]

When I tapped the mounts, it put the shaft in a near bind.I must change the angle of the mounting plane. Any ideas on transom weight? still 1# at transon while tilting on the back of the sponsons? The prop dog is too small for the larger prop. Where can I find a dog large enought for the X437/3 with a 3mm shaft? Do I have to fab?

[backwoods]

Guys, I ran a quart of fuel through the .21 Miss Bud tonight. Unbelievable to say the least! Although, I am shadowed by this guy with the .32 thread. That's awesome. CAn I safely use my .15 flywheel on the .21? I read his thread earlier today and thought the spring ideas was smart on the carb in case of a Rx failure. Today my shaft collet began slipping after the second tank and I had to tighten. In the process of tightening I pushed the connecting rod loose from the carb throttle arm without realizing. A bump or two after lauching the boat meant I got to ride a half tank of fuel out at top speed. The super rich setting and tight circles were the only thing that stopped catastrophy. I hope that I did not cause anybreak-in problems. More than a hand-full to handle at best. I saw the bottom of the boat twice and thought it was the end.
I plan to order a speedmaster rudder w/pick-up tomorrow. I also need my water outlet on the opposite side of the boat, or at least where I can see it turning right. Ideas?
I have a huge carbon fiber fin that HydroJ recommended, I know I need to shape it somehow. It holds the boat like an anchor in a turn, but will lift the intire boat in a left-hand turn. What shape should I mimic as I begin to tune the fin? It is visable in the previous photos. It starts as 1/2" at the top and widens to nearly an inch at the bottom.
Also, does anyone know of replacement servos similar to the Miss B that are 7.4volt 800mAh? I have these batteries and charger in a heli and love the light slim design. Sorry for all the ?'s, Any ideas please!

[backwoods]

OK, guys here's an update. The .21 is running in the low to mid 40 MPH's with the X437/3 prop. I can tell I'm not getting all the RPM's out of the .21. What is obvious is that I am not ready to see all the RPM's yet! Ihave seenthe bottom of the boat too many times to run full throttle. I need to make the turn fin smaller, but I do not know what shape to follow. Any left steering at all will flip the boat at near full speed. Ideas on shaping? I left the shape stock for safety, but bigger is not safer in this case. I never would have realized that a few MPH's would make such a difference. Yeah, I admit my rookie status here. Where are the ideas and input? or criticism? The wife should help this weekend with photos and/or a video. Hoping to see low 50's and I'll move on to the next project. Is there a tiny tacho that i can install for tweeking prop? I am growing lonely in this thread but, I'll keep posting.