K&B 3.5 outboard
03-14-2007, 08:28 PM
#27
RE: K&B 3.5 outboard
You got pushed into the laundry room with the hobbies huh? Don't feel bad it happens to all of us.....
That will make a nice place to store the whole unit when it's done. Its the "permanent" hinge pin location and the flop of the mount that makes handling the detached motor a hassle, and I don't like skidding things on thier side on a table...especially when so much time goes into stretching the buck on one of these motors. You'll appreciate it even more after the Irwin pipe is on.
An 1/8" Z bend specialty brass located each side of the transom mount would let you slide that puppy straight down without any screws.
I think I'll take that approach when I make mine! hehehehe........
Thanks for the idea, pal!
That will make a nice place to store the whole unit when it's done. Its the "permanent" hinge pin location and the flop of the mount that makes handling the detached motor a hassle, and I don't like skidding things on thier side on a table...especially when so much time goes into stretching the buck on one of these motors. You'll appreciate it even more after the Irwin pipe is on.
An 1/8" Z bend specialty brass located each side of the transom mount would let you slide that puppy straight down without any screws.
I think I'll take that approach when I make mine! hehehehe........
Thanks for the idea, pal!
03-14-2007, 08:33 PM
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RE: K&B 3.5 outboard
I just screwed two bolts in the backside they stay in the wood and finger on the nuts...washer is just a good place to take pictures when the "hobby table" in the kitchen is cluttered with parts....
03-14-2007, 09:33 PM
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RE: K&B 3.5 outboard
I gotta love crackin into a used motor,,,, sometimes....I would almost say this sucker is hot!!! mods I have found so far.....Sleave/block/rod possibly crank.....I asked someone and a 3.5 K&B should have 1 exhaust 2 transfer and 1 boost..Mine has an extra and all work done to the ports was very well done the exhaust was worked over sleave and block transfers in the block were all worked and extra added......When I get it all cleaned up Ill try to get some pictures of it!! Might just be why the red carb was on it I do have a gold carb comming though.. Im gonna get ahold of the guy I got it from and ask a few questions, more to come!
03-14-2007, 10:38 PM
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RE: K&B 3.5 outboard
piston is stock the rod is tpaered on one side which I usually do both sides, the sleave is hard to explane and rcu wont take my pictures 6 ports total including the split exhaust port block runners all match up to the sleave mods and there are a couple that im not sure how they got a tool in to do but was done well not all F-uped like some mods Ive seen and it has been run as there were sleave stains from the fuel, that tells me that it has been run for a few tanks of fuel with the mods done but it was all still tight....Now I need gaskets new bolts and some cleaning!
03-15-2007, 10:55 AM
#32
RE: K&B 3.5 outboard
Here's a three view of a stock sleeve.
First one is the exhaust port(s), its a double window, plunge milled, no reliefs.
Second view is the rear port(s). Angle milled from the bottom to provide boost to the head. No side angles.
Third view is the side port(s). Angle milled from the side to induce swirl. No upward angles.
The only thing I touched on this sleeve before I ran it was cleaning the chrome throw off the port lips with an 320 grit emery stick, and then buffing the inside chrome at the port openings only with felt dremel and light compound.
I checked the piston skirt with a flat 600 grit stick, hand wiped the bottom lip of the skirt with aluminum polish to break the corner to help blowby lubrication up the skirt on the downstroke.
After heat cycle break-in, and a gallon and a half running with 40% Cool Power all synthetic, the sleeve was checked and there was ZERO scoring with slight pinch still at the top. The piston had a nice and even chrome-like wear ring at the first 1/16" from the top.
This was where I stopped running it for the season and started to put time into it on the bench to make lower end improvements and new bearings. The top bearing started to fail and was risking hurting the front housing bore so it was time to retire it untill I could get to it. I hated to have to disturb the liner and piston with such a nice break-in result but the top bearing had to go.
I have decided to run 50/50 castor/synthetic from now on with my marine engines.
First one is the exhaust port(s), its a double window, plunge milled, no reliefs.
Second view is the rear port(s). Angle milled from the bottom to provide boost to the head. No side angles.
Third view is the side port(s). Angle milled from the side to induce swirl. No upward angles.
The only thing I touched on this sleeve before I ran it was cleaning the chrome throw off the port lips with an 320 grit emery stick, and then buffing the inside chrome at the port openings only with felt dremel and light compound.
I checked the piston skirt with a flat 600 grit stick, hand wiped the bottom lip of the skirt with aluminum polish to break the corner to help blowby lubrication up the skirt on the downstroke.
After heat cycle break-in, and a gallon and a half running with 40% Cool Power all synthetic, the sleeve was checked and there was ZERO scoring with slight pinch still at the top. The piston had a nice and even chrome-like wear ring at the first 1/16" from the top.
This was where I stopped running it for the season and started to put time into it on the bench to make lower end improvements and new bearings. The top bearing started to fail and was risking hurting the front housing bore so it was time to retire it untill I could get to it. I hated to have to disturb the liner and piston with such a nice break-in result but the top bearing had to go.
I have decided to run 50/50 castor/synthetic from now on with my marine engines.
03-16-2007, 10:41 PM
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RE: K&B 3.5 outboard
Very close to done now just slapped it back together so parts wont get lost waiting on gold carb to get here and hunting down a front bearing (top).....Its now all Stainless screws from top to bottom, no ugly rusting black ones thanks to james at twisted liquid for setting me up with the screws that nobody else had! Also 1200deg header paint on the header oven baked...I think Im gonna go with red fuel lines and red primary color for the hull....... Also might get frisky and etch something on the pipe!
03-16-2007, 11:20 PM
#34
RE: K&B 3.5 outboard
That's looking sharp. You'r going to have fun tuning and trimming. Outboards are fun to play with, there's a lot of variables to go through. You'll be suprised at what a little change here and there can do. The way tunnels ride really can make magnifications to tuning, unlike the more solid footed mono's or hydros.
My outboard is awaiting final assembly, but there's two more motors I have that are ahead of it that I've been working on that will share some of the same benchwork so those have to be caught up.
BTW what hull is going with the motor?
My outboard is awaiting final assembly, but there's two more motors I have that are ahead of it that I've been working on that will share some of the same benchwork so those have to be caught up.
BTW what hull is going with the motor?
03-17-2007, 12:36 AM
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RE: K&B 3.5 outboard
maus 3.5 tunnel....after engine is done Im gonna start work on it
LOL I to have another engine to build......Zenoah I have almost 1200$ worth of parts sitting and waiting for me to build my gas cat but im not even gonna start it till I have everything for it!
LOL I to have another engine to build......Zenoah I have almost 1200$ worth of parts sitting and waiting for me to build my gas cat but im not even gonna start it till I have everything for it!
03-17-2007, 06:17 AM
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RE: K&B 3.5 outboard
Watching this thread makes me want to go to work on my K&B. Toyota- that engine turned out great! I have a question for you guys- I have an older engine thats never been run, with a black carb. Whats the difference between the black and gold carbs? If the gold carb is better, will it fit on my engine?
03-17-2007, 08:57 AM
#37
RE: K&B 3.5 outboard
They all will fit. The Gold carb has less vacuum draw though, because its a larger throat diameter. There's been lots of discussion about it in one of these threads somewhere. The only cure is it run a very high tank location for me. Some have used a hopper tank mounted up high also. This is in reference to the SS stock setup, your older one might produce more exhaust pressure and wont be necessary.
03-19-2007, 01:32 PM
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RE: K&B 3.5 outboard
Just bought a 33'' dumas tunnel hull with k&b 3.,5 .21 with gold carb and a octura prop 3 bladed X437/3. Went to run it and no matter the tune of the motor was the boat would fire up out of the water and as soon as the boat hit the water it would cavitate and rev but then when the prop grabbed it just bogged the motor down about 20 ft away and in a cold pond its not ideal for retrieval. Is it Motor tune? too much prop ? Anyone? thanks
03-19-2007, 01:47 PM
#39
RE: K&B 3.5 outboard
Its that fuel draw problem or your needle is too lean.
Set your needle on-shore by bliping the throttle. When your close it should bog and almost want to die, then burst up and clear out. DONT keep your throttle pegged past finding out, or you'll over-rev the rod.
If that doesn't work, then its the fuel tank being too low. Put a foam spacer under it as high as you can and still fit the cowl. Check to see if your pressure line is working, or the system is plumbed right.
The prop you have is fine, it should not be overworking the motor. Set your motor with the propshaft even with the bottom of the sponsons or a touch lower (1/8" max), with a little bit of down-trim (2-3 degrees)
I think the hull you have is one step up from the 3.5 Dumas hulls. They are from 24" - 29" inches long if I recall.
Go to the Dumas site and see if you can match up what you have.
http://www.dumasestore.com/catalog/i...83dc7ed38230f5
Set your needle on-shore by bliping the throttle. When your close it should bog and almost want to die, then burst up and clear out. DONT keep your throttle pegged past finding out, or you'll over-rev the rod.
If that doesn't work, then its the fuel tank being too low. Put a foam spacer under it as high as you can and still fit the cowl. Check to see if your pressure line is working, or the system is plumbed right.
The prop you have is fine, it should not be overworking the motor. Set your motor with the propshaft even with the bottom of the sponsons or a touch lower (1/8" max), with a little bit of down-trim (2-3 degrees)
I think the hull you have is one step up from the 3.5 Dumas hulls. They are from 24" - 29" inches long if I recall.
Go to the Dumas site and see if you can match up what you have.
http://www.dumasestore.com/catalog/i...83dc7ed38230f5
03-19-2007, 05:07 PM
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RE: K&B 3.5 outboard
thanks for the information i only have about 1/2 an inch to move the tank upward before steering interferance in that enough or sould i try moving the steering cables upward as well. Will let u know the outcome.
03-20-2007, 11:53 PM
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RE: K&B 3.5 outboard
hay jet I have a question about the disk break quiet...does it set up or stay tacky and how does it hold up? parts store people couldnt tell me crap about it..oh and how after applied do you need to wait before using the engine?
03-21-2007, 01:00 AM
#43
RE: K&B 3.5 outboard
It sets up nice! When I did the brakes on my car, I realized this was the stuff I've been looking for. Forget silicone RTV, that stuffs a mess and it stinks.
This acts like water based latex - which it probably is, it doesn't say. It sets up pretty quick, and its way less of a mess. It cures within minutes in a skin coat application, or a close fitting joint. Any extra you just rub off with your finger like rubber cement, only its not gummy sticky like rubber cement is.
I am definetly going to use it on my outboard to seal the drive on it. I know it will hold up, and when it comes time to split the halves, I know its going to be a breeze to pull off, plus it's tinted...its easy to see where its going, or what more needs to come off.
I put a motor together with it instead of rear plate and front housing gaskets. I haven't run it yet. I really don't think nitro is going to affect it, plus its made for the back of brake pads...I don't think it will burn off, even if used near an exhaust.
Hobby Lobby or Michael's Craft stores will have the empty applicator bottles with the pin-point tip. I think they are less than a dollar. The bottle is the way to go, you can draw a super fine bead with it, and if you mess up just wash it off and try again, no thinners needed. If a little squeezes out when you put it together, you just use a damp rag wipe it off. It doesn't smear and stick like RTV does.
I'm anxious to test it out more, but so far I think it's the answer. I know it will work fine sealing the drive unit, but still wondering about the powerhead...but I'll bet you ten bucks it holds up.
I went with a real fine bead around the inside shoulders on the PTO (backplate), and the front housing. Just enough to take up the air gap of the chamfer on the case when it gets slid together. Study the area first, plan how much to put down, and where the sealer will actually spread to.
I learned a long time ago, go for a standing thick bead where there's a good air space to fill up, instead of buttering up the whole flat surface. It is easier to twist or pop off when its time to dig into the motor again. Never use sealer like your gluing, or otherwise it's pry-bar time when it comes to take apart.
This acts like water based latex - which it probably is, it doesn't say. It sets up pretty quick, and its way less of a mess. It cures within minutes in a skin coat application, or a close fitting joint. Any extra you just rub off with your finger like rubber cement, only its not gummy sticky like rubber cement is.
I am definetly going to use it on my outboard to seal the drive on it. I know it will hold up, and when it comes time to split the halves, I know its going to be a breeze to pull off, plus it's tinted...its easy to see where its going, or what more needs to come off.
I put a motor together with it instead of rear plate and front housing gaskets. I haven't run it yet. I really don't think nitro is going to affect it, plus its made for the back of brake pads...I don't think it will burn off, even if used near an exhaust.
Hobby Lobby or Michael's Craft stores will have the empty applicator bottles with the pin-point tip. I think they are less than a dollar. The bottle is the way to go, you can draw a super fine bead with it, and if you mess up just wash it off and try again, no thinners needed. If a little squeezes out when you put it together, you just use a damp rag wipe it off. It doesn't smear and stick like RTV does.
I'm anxious to test it out more, but so far I think it's the answer. I know it will work fine sealing the drive unit, but still wondering about the powerhead...but I'll bet you ten bucks it holds up.
I went with a real fine bead around the inside shoulders on the PTO (backplate), and the front housing. Just enough to take up the air gap of the chamfer on the case when it gets slid together. Study the area first, plan how much to put down, and where the sealer will actually spread to.
I learned a long time ago, go for a standing thick bead where there's a good air space to fill up, instead of buttering up the whole flat surface. It is easier to twist or pop off when its time to dig into the motor again. Never use sealer like your gluing, or otherwise it's pry-bar time when it comes to take apart.
03-21-2007, 07:45 AM
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RE: K&B 3.5 outboard
ORIGINAL: fstwalker
Just bought a 33'' dumas tunnel hull with k&b 3.,5 .21 with gold carb and a octura prop 3 bladed X437/3. Went to run it and no matter the tune of the motor was the boat would fire up out of the water and as soon as the boat hit the water it would cavitate and rev but then when the prop grabbed it just bogged the motor down about 20 ft away and in a cold pond its not ideal for retrieval. Is it Motor tune? too much prop ? Anyone? thanks
Just bought a 33'' dumas tunnel hull with k&b 3.,5 .21 with gold carb and a octura prop 3 bladed X437/3. Went to run it and no matter the tune of the motor was the boat would fire up out of the water and as soon as the boat hit the water it would cavitate and rev but then when the prop grabbed it just bogged the motor down about 20 ft away and in a cold pond its not ideal for retrieval. Is it Motor tune? too much prop ? Anyone? thanks
Hey TT it looks great. I hope to have my OB piped before its next outing. Looking at yours makes me want to get working on it!
Ryan
03-21-2007, 09:13 PM
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RE: K&B 3.5 outboard
Here are a couple pictures of my tunnel so far its a maus not made anymore so giving it kinda a retro look..dark matalic red and bright white the cowl still needs some glass work so Im kinda in the middle of that gotta picture it with white at the bottom (of cowl) and red on top kinda following the body line..At least thats the plan so far.......
03-21-2007, 10:05 PM
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RE: K&B 3.5 outboard
Thanks And I cant hardly wait eather!! Just have to build a boat stand before I can put it on...For a stand Im thinking about using a plastic cutting board with PCV comming up from that with a slot for the skeg to set in any tunnel stand ideas are welcome!
03-21-2007, 10:21 PM
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RE: K&B 3.5 outboard
That's an interesting idea. I myself is in need of some sort of stand. A guy that I race with likes to make his stand support the load caused from when the starter is pressed on to the engine. My 7.5 tunnel started to crack on the top of the transom and I believe it would most likely be from the load on the engine. I do have to press quite hard to produce enough friction to turn the engine over.
I'm not too sure of the best route to take in building stands.
Ryan
I'm not too sure of the best route to take in building stands.
Ryan
03-21-2007, 10:33 PM
#50
RE: K&B 3.5 outboard
You're definetly going to want a nice snug slot for the skeg to fit when the boat is put on the bunk to start it.
My first season of running, I was just starting it on a picnic bench, and holding the motor firm with my hand as I bumped the starter.
This I think help contributed to the front bearing failure because sometimes the starter would jump around on the flywheel. It takes a little practice to get smooth with cone starting one of these.
I usually turn the crankshaft at the bottom of the stroke, so it has a run on the compression. Then I put the starter down on it centered as I can, and then juice it.
Bump starting it with the starter is a bad idea - that's when it has the tendency to jump around. Just get the piston ready, and press the starter down and then hit the button and let it rap till she pops off.
For the motor builders, I started a thread in the "Glow Engines" Forum for hopes of people helping to identify all the different versions of the sleeves for this 3.5. There have been four revisions, and the MECOA site I stay away from as much as possible for an in-depth question, and to call them it requires they CHARGE you for MONEY to talk to someone in the Parts Department by APPOINTMENT ONLY.
Any help with posting scans of old manuals or such would be awesome. The thread is called "K/B 3.5 Bench Notes".
This I hope covers ALL the verisons - Aero, Ducted Fan, Old I/B, New I/B, and our O/B's. I would like to know what can be swapped out, or properly ordered.
My first season of running, I was just starting it on a picnic bench, and holding the motor firm with my hand as I bumped the starter.
This I think help contributed to the front bearing failure because sometimes the starter would jump around on the flywheel. It takes a little practice to get smooth with cone starting one of these.
I usually turn the crankshaft at the bottom of the stroke, so it has a run on the compression. Then I put the starter down on it centered as I can, and then juice it.
Bump starting it with the starter is a bad idea - that's when it has the tendency to jump around. Just get the piston ready, and press the starter down and then hit the button and let it rap till she pops off.
For the motor builders, I started a thread in the "Glow Engines" Forum for hopes of people helping to identify all the different versions of the sleeves for this 3.5. There have been four revisions, and the MECOA site I stay away from as much as possible for an in-depth question, and to call them it requires they CHARGE you for MONEY to talk to someone in the Parts Department by APPOINTMENT ONLY.
Any help with posting scans of old manuals or such would be awesome. The thread is called "K/B 3.5 Bench Notes".
This I hope covers ALL the verisons - Aero, Ducted Fan, Old I/B, New I/B, and our O/B's. I would like to know what can be swapped out, or properly ordered.