26 briggs aircooled yamaha 50 project

[igotit]

My mower started hangin around with my old pro 50,stayin out late.....one thing lead to another....4 days later the briggsmaha was born.
Ill go into detail with pics a lil later.

24 mph in was my best speed.motor is on a heavy 17ft duracraft thats rated for 90 hp.

Watch "26 briggs ontop 50 yamaha" on YouTube
https://youtu.be/NgYEhlA4cSw

 

[igotit]

Picked up a used yamaha 50 blown powerhead for $100,used husqvarna mower blown deck spindals for $150,boat is a 1968 duracraft bass boat converted to open hull layout....$500.

Guttef the 50,chopped splined crank stub,had a machine shop build a steel 4140 coupling to handle 4k rpms and 60flb torque....freebie.
Free steel to build adapter plate,free yamaha control box.
$800 invested
Wired up yamaha control box to work with briggs wiring,made shifter linkage using yami parts.....increased briggs throttle stroke from 1 in to match control box travel of 2 1/4 in.

Bottom line....it all works well.

 

[steelespike]

A very nice result. What is the wide open throttle rpm? What size prop? As you may know a marine application needs to operate within the motors wot rpm rating.
It appears your likely at or close to the needed rpm.

 

[robert graham]

That is great!...Your name must be McGyver for sure!.... I'll admit to being very envious of folks that can doing things like this!

 

[igotit]

A very nice result. What is the wide open throttle rpm? What size prop? As you may know a marine application needs to operate within the motors wot rpm rating.
It appears your likely at or close to the needed rpm.

In the video my rpm was 2600,but that may not be accurate.....im running a cheap mower tacometer.
Wheel size....i dont remember exact size at the moment.its a stock pro 50 wheel with 15 in pitch.

As for rpms safe limit,the engine is built to safetly handle 3600 rpm loaded by the manufacture.

This engine can be pushed to over 4krpm....but eliminates any liability from manufacture in event of failure above 3600 rpm.

I have a few wheels to try,i have a 35 merc 15 pitch,a 40 merc 16 pitch....but i think they will all give me similar results

 

[steelespike]

Using our known numbers and one guess I get about 3600 at 24 mph.
15" pitch,12% slip,1.92 gear ratio,24 mph = about 3600 rpm These results depend heavily on
the accuracy of the numbers.12% slip is a guess based on typical slip on the usual runabout or utility.

 

[igotit]

Im not so sure on my rpm at the moment.my lil tach was kinda acting up today on a 4 hour ride.i used gps ,18 mph
Acording to my tack at 1600 rpm.
I reset my govner not to turn up as high.

Every wheel i have seems to be too big.
I get best topend with the 50hp wheel,i get best hole shot with 35 wheel....but slower topend.

Not really trying to go fast,but now im curious of how fast and reliable i can make this rig....lol
My hull weights around 1000 lbs,its a old 17x54 welded hull.
Thats pretty heavy in my opinion.
My original intention with this build was to install it on my 18ft surecast trihull,build a cabin and make it slow over night cruiser.
Eitherway im impressed with the performance i have now.
I may save some cash and have 1 of the wheels dropped to a 12 pitch,then govern the engine for around 4k rpm loaded.

 

[PS94]

This is amazing...I have an old outboard...I have a few of these Intek motors.....

 

[igotit]

Cant wait to see another build,keep us posted

 

[gm280]

I have to admit I am really impressed at all the effort and thought put into this mix up assembly. I see an amazing marriage of the two different machines. Now you have to manufacture a cowling with some metal/fiberglass for that custom finished look. :thumb:

 

[igotit]

I thought about a cowling....but motor already looks bulky.
The briggsmaha is heavier than my 70 johnson.
Besides the looks....shes a great machine.
I only wish i could afford a 40hp verticle shaft,i even thought about a 22hp vtwin diesel engine.
The build really was easy,been wanting to do this since 1994

 

[igotit]

The best feature about it.....cheap.
Rode for 4 hours yesterday,burned 2 gals of fuel @ $1.80 per gal....cant beat that.
Its a reliable engine,parts are cheap and easy to repair.complete new 26 intek is around $700
I have another build comming up,a old 15 hp suzuki with 7hp briggs,and a 25 evinrude with 19 or 21 briggs

Keep an eye out
Briggzuki and briggsirude comming up soon

 

[64osby]

There is a guy that I've met several times that takes old Eska lowers and mounts new Briggs 5 hp to them. He has been making and selling them for years. Uses a thick milled aluminum plate and an impact socket for the coupler. Sells them for $500 with a warranty as I recall. His best market is brackish water Gulf states.

 

[GA_Boater]

Is this your helper, igoit?



Good work on the FrankenBriggs! :thumb:

 

[robert graham]

Maybe 1/4 inch aluminum plate or 1/8 inch stainless for your next one, just for corrosion resistance???....

 

[igotit]

Decided to start saving up to build my camp boat to utilize this motor.
I have a mid 80s 18fy surcast trihull that needs new floor,im thinking a 10x5 cabin,just enough room for 2 small beds,tiny camper size bathroom and kitchen area with a helm.
Aiming to do estimated 8 mph cruise speed,low rpm and fuel consumption.
Gonna be a slow build
Really wanted to use my 21ft carolina skiff....but having registration issues with previous owner.
I even bought a used 27ft fleetwood camper for the appliances to use in the 21....but all thats on hold.
So my only viable option is the 18ft trihull for now

 

[igotit]

Ive lowered govner and put on a 35 merc 16p prop,slower topend but better lowend and fuel economy.2.5 hours full throttle on 1 gal gas.
Also added inline electric fuel pump.

Watch "Homemade outboard motor" on YouTube
https://youtu.be/8oJngqX6XTA

 

[roscoe]

cool

 

[igotit]

Almost every homemade outboard motor thread or vid you find,has poor performance results.glad i finally was able to achieve respectable results from such a heavy boat.
Im thinking about lifting the motor 2 in higher and running the bigger prop surface drive in an attempt to gain a lil more speed.im happy with current speed....but id like to break 30 mph....just to say i did.
My 70 johnson on this 1968 duracraft only did 31 average with 34 mph being the best.

 

[HT32BSX115]

That is VERY COOL! Those Vanguard engines are great runners!!

I also like the diesel idea! The only change I would probably make would be to use aluminum plate where you used steel....... You might save some weight.

The other thing you might consider would be a flexible Buna (or other) coupling to reduce vibration and stress on the vertical shaft.
http://www.surpluscenter.com/Power-...-SPLINED-L-110-JAW-COUPLING-HALF-1-3423-9.axd

If you can get that BS engine to turn 3600 at Wide open throttle, your choice of ratio and prop are pretty close to optimum!