Briggs 6.5 hp flathead running at 4000 rpm?

[Nosandwich]

I will clarify more. This project does exist. It is a functional outboard motor with the Briggs engine mounted and working, replacing the original Evinrude power head that was frozen. I am posting here on diykarts because I figured there was a wealth of knowledge about small engines here, including my 6.5 hp Briggs engine. Below is a picture of the project. The motor is usable as is, but I am always looking to tinker with or improve it. My question is legitimate. I use the motor on a 10 ft aluminum boat and was brainstorming the other day about how to get more than the 7mph top speed I got on my last run at the lake. Which is what led me here to post about adjusting the governor.

Let me guess. There is a plate on the transom that says 5hp max? I have a 10' jonboat and a 2 hp Johnson. 7mph is pretty darn good.

But, that's human nature, why be happy with something when you can screw it up and wind up on Gilligan's Island???

Good luck, we'll help as much as we can. ( Just remember the paddles. )

 

[ezcome-ezgo]

I've always believed in ducted props.

 

[bikerider]

hm.. not entirely sure but I found a manual that might cover your engine..
(120000 series.. might include the 123k00 *shrugs*)
http://faculty.missouri.edu/~schumacherl/276781SingleCylinderOHV.pdf

it tells you HOW to reset the governor but unfortunately refers to a different manual to
get the values to set the governor TO. (B&S sometimes is just BS)

Anyways,
the numbers are to be found here:
http://www.mymowerparts.com/pdf/Bri...ent-Engine-Information/123K00-MS6872-0406.pdf
But unfortunately although it claims to list all numbers for 123k00-123k99
I cannot seem to be able to locate 123k12 in there.



The highest rpm to be found in that manual is 3800 rpm btw
if that's close enough for your needs.. you might be able to go with that...
I can't tell for sure, but personally I'd call that safe enough for me to try.

Since that's not my engine I can't but tell you to NOT TRY if you want that engine to survive of course.

at least until you found the correct manual that tells you differently.

'sid

I think my engine may be included in what you found. I have heard of it referred to as a model 12. Thank you for the link. Perhaps 3800 will work well for me. I will have to see once my digital tachometer arrives and I can go from there along with a couple water tests.

---------- Post added at 12:12 PM ---------- Previous post was at 12:10 PM ----------

Can you change the prop like they do on jet skis for more speed ? Seems like a easier way to me and safer if you can.

Yes, that is an option I have been considering as well along with modifying the governor. The stock prop on the lower end is a 2 blade 7 1/4" pitch. I found a 3 blade 8" pitch that I may pick up for it.

---------- Post added at 12:30 PM ---------- Previous post was at 12:12 PM ----------

I've always believed in ducted props.

I had to google ducted propellers and I'm glad I did. That's quite interesting. Now I will have to take a look around and see if that's an option for my motor.

 

[bikerider]

I have mounted my digital tachometer today and ran the motor a bit. At full throttle with the governor un-modified, the tach reads roughly 3650 rpm. At the lowest throttle I can do without the engine shutting off, it reads roughly 2550 rpm. The low end rpm seems high to me but this is the first time I've had a tach on a small engine. If my tach is to be believed, it looks like my engine has the standard 3600 rpm governor limit. I have removed the stock exhaust and ran it to below the water line so next time I test run it I hopefully will not be exhausted out.