need help with 18 hp opposed

i have a old amphibious 6x6 that im thinking of putting an 18 horse opposed briggs in, really only because its what i have.
i dont want to do anything performance wise to this engine, just get it in and running and i dont know much about small engines other than what could cross over from automotive.
so my question(s) are,
what do i do about the governor, can i just run without it, hook the throttle cable directly to the carb and can i leave the governor parts in the case? or should i hook the throttle linkage to the governor so i dont over rev it, or if i do that will it not throttle right while im driving?

ive read these arent strong engines, but if im leaving it stock and not trying to race it is it strong enough?

appreciate any help ya'll can provide

Personally I would just hook it up to the stock throttle location.  If a foot throttle, add a return spring to help it return back to idle.  If it is a dash throttle, then you should be good to go.

yeh, foot throttle

I would think that keeping the governor intact would be good on one of those amphibious machines. 18hp should be enough to pull you around decent, but I would guess you don't need to be on and off the throttle that much, not like a tractor or go kart anyway.

You can use a foot pedal either way with the governor stock or removed. With the governor stock, I think you'll find the foot throttle is sort of an on or off kinda deal. With the governor removed you'd have a bit more control over it but of course would be more prone/tempted to rev it higher.

You have to run them fairly hard to blow them up, but if you run the engine up really high all the time, then it can happen. Many people report low oil being an issue with these blowing up. The vertical shaft engines have two plastic paddles in the bottom and when the oil gets low they don't throw the oil around as well.

sorry i didnt specify, it is a horizontal shaft

I'm really not sure why someone would say the Briggs oppy's aren't strong engines, haha.

Welcome to the forum by the way!

AllisKidD21 wrote:

I'm really not sure why someone would say the Briggs oppy's aren't strong engines

Yeah, I was like, "Not strong??? Than what is?", LOL.

An oppy should work fine on it. They have PLENTY of power. Whoever told you Briggs oppy's aren't strong is wrong. Most oppy's are getting old and could probably use a valve job but that's it. It'll serve you well if it's kept up.

i had read somewhere that someone said they werent very strong engines, weak crank i think they said? also read flywheel cant take more than 4k rpm. ??
and thanks for the welcome!

Well, the flywheel can take it, but not like a billet one would. You might get away 4k, but that's tops with all stock parts. You can run them higher, but only for a short amount of time. I run my single cyl. at 6k all the time, but no more than like 6 seconds at a time. Does that make sense?

They aren't weak engines at all. You might have read that on a lawn mower racing forum or something, because they replace every part on the engine with something better because they're constantly running at 8k. It would be considered weak for them.

i bet i did read it on a racing forum.

so if i bypass the governor can i leave the governor parts in the case without hurting anything? or does it need to be removed?

Most people recommend taking them out so they don't come apart. You can also hook a spring to it to hold some pressure against it and leave it disconnected. That saves taking the engine apart. Apparently, when they are disconnected they can flop around and come apart. I haven't seen it happen myself but don't know. On my own engines I usually remove the gov shaft and screw in a sheet metal screw coated with permatex black silicone. Or you can remove the parts and just leave the shaft in place. I forget how they are arranged inside.

The horizontal opposed engines will have a dipper on one of the rods, just like the smaller single cylinder engines. They might not be as prone to low oil issues as the verticals. Even so, if you keep it filled up you should be ok.

As far as being strong engines, I think the racing guys are mostly talking about high rpm use or very hard use. Unless your gonna really beat on it, it's no worse than anything else. Guess the cranks might flex more than other designs in a race application but you'd think the v twins would do the same. Don't really know if people had a lot of crank issues or not. As far as I know the most common thing was low oil or breaking the plastic oiling paddles.