Another lonely boat followed me home...

[bogieboy]

First mockup of the exhaust, being a 4 stroke it doesnt need an expansion chamber, all piping is the same ID as the exhaust port, and muffler is a glasspack for 1/5 scale buggy tuned pipe stingers...so rated for 25-30cc motors... i am thinkimg of extending the pipe so the tip of the can is roughly even with or slightly protruding from the back of the boat, to keep any oil drips off the boat...

[Jesse J]

Rudder looks like a good distance and aligned well front to back.
Brass or even aluminum breakaway screws would be good. If you can get the top screw tight enough, plastic will work. Even a short piece of brass tubing with a zip tie to hold it.
Creative build, nice job!

[bogieboy]

Thanks! In all my reading it seemed that parralel or slightly behind center of the prop was roughly the best all around placement for the rudder so i made it just a hair past centered...i ended up just going the shear bolt route, i currently have an m4 in it because its what i had...LOL the top pivot is a solid steel pin, not too worried about that... i may back off to the brass idea eventually, but for now its steel... i try to avoid anything big enough to cause issues...LOL

[bogieboy]

Sounds of victory.... fun fact, a Stihl 4mix engine with an 8" black pipe exhaust with a glasspack is actually quieter than a stock 4mix....LOL

https://youtu.be/tJW9bCFHmys

https://youtu.be/TNoZRh1VjLo

[bogieboy]

Win of the day.... fuel system-sorted. Flex shaft-cut. Stuffing tube-cut and bent. Driveline-success.

https://youtu.be/OoCY6XKsnsI

[bogieboy]

Just got the rudder mounted as well...

[bogieboy]

First of several black basecoats on.... gonna lay up maybe 3 coats, color sand, 3 more, then lay flake over it.... bottom will be traditional white/cream color...

[bogieboy]

so, havent gotten the flake done yet... but.... progress.....hehehe

the good... she seems pretty well set up with my eyeballed settings.

the bad... i didnt get the stuffing tube sealed perfectly.

the ugly... right after i got this clip i lost the engine died... i had a fishing pole, but that promptly got snagged on everything but the boat... waited it out and it drifted with the wind/current to wheere i could tie a half full pepsi bottle on the end of the line and throw it since my luer was not working too well.... all is well, just need to figure out the stalling..... it fired right back up...

[srislash]

Ok what was the fuel/oil mix? The engine will shut down due to heat from being lean.

[bogieboy]

fuel mix was 50:1, premium non ethanol fuel and stihl hp ultra mix. same mix i run in everything 2 stroke, including my 94cc chain saw.... and the carb was tuned to the rich side of things.... i wanted to try and get a temp reading on the head but it took 45 min to recover the boat, due to me not wanting to drown in 45°f water... next time i run it will possibly be at a friends pond.l with a jon boat at the ready....

[bogieboy]

also of note, the ebgine is a stihl 4-mix engine, so a 4 stroke that has no oil resevior, and is oiled thru the fuel mix. it did not exibit any sort of sigbs of having gotten to a soft sieze situation, it just acted like it got starved of fuel.

also of note, the engine is potentially tired....LOL it was floating around the small engine shop that i work at for a year before it came into my possession. (i am a Stihl Certified tech also fyi...LOL)

[srislash]

I had stated as my pal got some ‘pre-mix’ fuel from hardware store at 50:1 and it did same thing. I’ve been told 25-30:1 for gas boats

[bogieboy]

good to know, i will try again with more oil....LOL i just kinda figured if stihl says you can run a 94cc saw and work it hard that 50:1 would be fine for a boat....LOL maybe i was way off....LOL

[bogieboy]

so, after a long summer of not running the boat due to house stuff( bunch of projects that needed done) i finally got to get it wet again. i did previously trace the running issue back to the carb being bad, as it wasnt priming up quite right, replaced it and got to run yesterday, ran 7/8 of a tank thru it with no stalling issues.... had a few other issues crop up though...

i swapped the 1.6p 78mm 2 blade out for a 72mm 1.4p 3 blade since i thought the motor was loaded a bit too much originally, but that could have been due to the carb.... with the 72mm 3 blade, the thing had really bad cavitation though.... if i went over half throttle out of the hole, it would blow out and not go anywhere... fun fact, stihl 4 mix engines run really crappy at half throttle....LOL once on plane it was good, but out of the hole sucked... the original 78mm 2 blade popped out of the hole fine.... would it not having been sharpened cause really bad cavitation?

also, at the very end of the tank, the flex let loose, got it home and found the Loctite bond had failed in the flex coupler at the prop shaft. would i be better off running silver solder on the flex coupler?

[Jesse J]

I’ve had a slew of loctite shafts come loose lately, so yes silver solder (done right, with thorough cleaning) should be better.