I built a mad motor BASED longtail (I gave it a total overhual of my own design), it runs great but the top bushing area of the housing gets EXTREMELY hot!!!! To the point u can splash water on it and it just boils and sizzles off after running it about 45 mins straight. Any suggestions?

a blade on your prop is bent or your shaft is where it comes out of the tube.

that, or your top bearing is shot.

bent prop blade caused it for me once. the unequal forces on the shaft from the bent blade causes the shaft to put unequal pressure on the bearings.

or, you screwed up your alignment when you built your frame.

Alignment, lubrication, angle, warp...
So many variables

Are you using a bearing system or just bushings and seals?

The props brand new, everything spins freely by hand i rechecked the alignment and my shafts not warpped. Im using bushings and seals with an autolubricator less than 2 inches away from the spot thats getting hot. Its my first build it has less than 2 hrs on it... is it possible the bushing just needs to be broke in? my autolube has the mid spring in should i put the heavy spring in to give it a lil more grease? other than this slight problem this thing runs GREAT!!! Im gonna get some pics up soon

i changed out my bushings once and it did the same thing the old one was fine the new one got hot as sh#t so i did away with it and fitted a sealed roller bearing on the top end its cool as a cucumber now

The top cap should be loosened when you add grease if you are running the old style set up. It will allow for any trapped air to come out. The auto lubricators are for upper bearing set-ups. Do you have a center bushing to eliminate shaft whip?

i'd say alighnment. pop you're end cap off and get some .002 .004 thou shim stock, cut a piece into a 1/4 strip the length of your bushing. slide it around the bushing until you feel a tight spot, loosen your motor bolts and tap the motor until there is clearance all the way around. the bushing does have a couple of thou clearance over the drive shaft right?

I can just about promise you that you don't have enough grease in the driveshaft tube. I ran into the same exact problem. The bearing closest to the motor was getting extremely hot. I thought I had plenty of grease but I was wrong. After I put plenty in there and ran it for an hour straight I had ZERO problems.

Alright guys it all sounds good! right now i have it tore down for paint so after im all painted up im gonna put that strongest autolube spring in but first put a grease fitting and manually pump in good ole GREASE!!! and put the auto lube back on. Thanks for all the input. anybody in south ga?

Now you on the right track.

we have built several of these, the issue with the mad mud motor plans is it calls for only 1 grease zerk below the center bushing but does not have a grease zerk above the center bushing.

if you read a go devil owners manual it states to never put grease in the shaft with the auto lube, but that you need to pump grease into the shaft until it "backs up" into the auto lube about half full.

so we put a grease zerk above the center bushing and also below the center bushing when we build them for people pump the shaft up till the auto lube backs up half full and have no issues.

the first one we built we did not do that and had similar issues until we finally got enough grease in the upper shaft. Usually the auto lube will explode or pop the cap off if you only try to fill it thru it and it will blow up before you get enough grease in it.

glad to be of help

after I built my second. I put the zerk below middle bushing. Used roller bearing and triple seals on bottom and double on top. /have auto lube 3 inchs below top bearing. took seal caps off and pluged auto hole and pumped the shit out of it till I saw new grease top and bottom. then installed auto and seal caps. then pump grease till auto was half full. Evertime I go it takes about 4 pumps of grease in zerk below bushing to get lubricator to move. Have used all season and no problems.

if you bought store bought bushings... the have a tolerance of +/- .05". If it has a 3/4 id and is on the minus side of that tolerance you will have a major problem. grease will not help this and it will not break in. It will heat up and melt thus causing it to fail and will also damage your shaft. I can't believe if it got that hot it hasn't already. I bought three different bushings and only one fit right. Go devil manual says to ream them out to a certain tolerance??? I dont know why everybody thinks if something on a longtail aint right just pump it full of grease??. If that bushing/wont slide on the shaft from one end to the other freely then thats your problem. Even though I'm acting like and expert ....I'm not I just did the same thing on my first build.

Im just saying how I made shur I had grease throughout my shaft and not air trapped. Used bearings top and bottom on this motor and really like it. Put it through HELL this season and was great

the simple solution would be to use a bearing at the top so the shaft floats in the housing untill it contacts the bronze bushing at the bottom of the shaft.

I was reading this post on the top bushing getting hot and I am having the same problem, although maybe not as hot. Does anyone have the numbers of the roller bearings that you would use for the top and bottom if you replaced the bronze bushings. Also should the 3/4" shaft turn freely with out any resistance to speak of in side the bushings? It sounds like the roller type bearings would be the way to go plus putting another grease zerk above the center bushing. Thanks for any info and input.

you need a bearing housing designed for thrust loading to change over, you can't just swap a bushing for bearings. you can buy what you need from a mm manufacturer.

if you make a housing yourself, just bring the inside (.75) and outside diameter to a industrial supply warehouse and they can look it up.

I checked the motor out this P.M made sure it was inline (motor shaft & drive shaft), put another zerk below the auto greaser and pumped it full both top and bottom, fired it up and let it run for 10 min. or so. Then I checked to see if it was still warm and it was on top not real bad but was hotter in the middle. What I am wondering is would it run warmer if it is out of the water where it can't be cooled than if it were in the water? Also in the MM plans it says to grind the outside of the bushing so it will fit inside the tube, I am wondering if this uneveness of the OD of the bushing can cause it to be a little out of allinment, thus causeing it to bind a little and warm up? It doesn't vibrate what so ever as far as that goes just heats up the shaft.

the water will definately make a difference in the temp on it, it will get warm just from the friction
run it like you stole it

what is the I.D. or your center bushing? a center bushing has .040-.050" clearance. it should not be getting hot and you should not have trouble pushing grease past it. the center bushing is not for alighnment, it is to control shaft whip. how are you holding the center bushing in place? when i installed mine i used a grease zirk to hold it in place. i grease my housing through the center bushing.

The center bushing has the same clearence as the lower and upper 3/4" I.D., 1" O.D.. I have my center bushing held in place with a set screw and a jam nut welded to the tube as well as the upper and lower bushings .

open up the id of the center bushing 13/16 to let grease thru. i cut small grease grooves in the outside of the bushing to allow flow also. Is the same center id in the mad mud motor plans? why would you need center alignment? if you were to have a slight bend in the housing you could never get it to work properly. also unless you really knock the crap out of rocks and stumps the center bushing should last years and years since it only touches the shaft when its torqued.

The I.D. of the center bushing is the same (3/4") as both the top and bottom bushings, and yes that is what the Mad Motor plans call for. I haven't hit any solid objects with the motor since I have built it and probaly don't have over 2 hrs. on the whole unit. One thing is should the shaft turn freely once it is in the tube and fitted thru the bushings? This shaft will turn but NOT spin as such.

open the center bushing up and then make sure shaft is centered on end bushings, if there is no grease on shaft and you have it centered it will spin freely. if you are using a set screw on the bushings you might be pinching or throwing the bushing off center. did you run a 3/4 reamer or a 3/4 drill bit thru bushing after you installed it? also as in my earlier post run did you run shim stock between shaft and bushing to check for clearance?

I haven't checked with shim stock yet but will, and am going to replace all bushings after I turn down the O.D. of all three bushings so they are all even and not high or low on one side or the other also check the inside clearence while I'm at it . Thanks for your input. Will let you know how it turns out.

ok man i went thru the same stuff in the beginning and have one homemade of my own. i like flange bushings myself. get the longest bushing you can find 2-3" 1 1/4 od x 3/4 i.d. and turn down the o.d. til its say 005-010" over shaft housing i.d., then use a press fit. then after you install the bushing ream it out so you have .003" each side or .756". but you get what im saying as to hook up motor and ujoint and shift the motor forward or backward, left or right, til the drive shaft is centered in the bushing? when you get that right a bushing will last a long time as long as its kept greased. Good Luck.....

One quick question, do you still use the center bushing so as not to have any "slop"?

I dont think you even need one really. they are just to extend the life of the shaft and bearings when hard objects are hit the shaft will bend from torque or "whip". i was updating my 86' godevil and asked warren c. and he said its been running this long without one why worry. I run rocky rivers so i installed it anyways but it does not touch the shaft it has at least 1/16'' clearance. it has no effect on performance other that the whipping when the prop hits an object. take that center one you got and open it up, then instead of a set screw run a zirk fitting into the bushing to hold it. then you have a place to grease instead of putting fittings on all over the housing.