New Engine To Replace 3.5 Briggs?

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Nov 16, 2009
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760
Location
Wisconsin
I have an older ‘Power-Tow' for moving light planes. It's likely over 35 years old, solid shape, but almost impossible to start. I tried the carb cleaning & refurbishment. It also been to a small engine shop, no appreciable improvement. My next idea is to get a new engine.

I just want something I can start without resorting to starting fluid & a 20 minute ordeal.

Here are the engine stats, 3.5 HP. Any tips on a direct replacement, Briggs, Honda, or whatever type?

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Would it bolt right on? Minimal fuss? As one would imagine, this is a very low hour setup, averaging, 20 minutes every 10 days.

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You could probably find a brand new $150 lawn mower with that family of engine at your nearest big box discount store. Strip that engine and bolt it to your setup there.

Have you tried to simply replace the carburetor? Just because it's been to a small engine shop doesn't mean it's been to a good one. Seems like it's in pretty decent shape. However, it has been 35 years. Just thinking out loud here.
 
Isn't there more to it that ‘bolting' to my setup? Are they standard mounting patterns? What about shaft setup?
 
I have a mower with a similar Briggs engine. If the primer bulb is not working correctly, it is very hard to start. Try removing the air cleaner and use the primer to see if gas squirts down the throat of the carburetor. Even if you end up replacing the primer or the whole carb, it would be cheaper than a new engine.

Andrew S.
 
I have a new primer bulb, gasket & carb cleaning, & a few other things. At this point I was planning on changing directions.

Yes, the shop may of been suspect. Total carb replacement may be an idea.
 
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Most engines are pretty standard. If you had to drill one new hole, it's not that big of a deal, is it?

Looks like the thing is belt driven, so any engine you get, you may have to get a different pulley for the crank of the engine if the one currently on there doesn't fit exactly.

Different engine makers have different crank shaft diameters, so the pulley may not fit a replacement engine.

I would be more concerned about the crank diameter than I bolt line ups.

I've replaced a B&S with an Harbor Freight engine and it bolted right up to my mower deck. The crank was different, so I needed different hardware to mount the blade.
 
No, not a biggie, new hole. I may look into carb issue again before a new engine. This engine has low hours, just needs to start MUCH easier.
 
If you do get a new engine, I suspect the one currently on there has a 7/8" diameter crank. Many of the HF engines are 25mm, so a new pulley. Obviously, measure the distance of the pulley from a fix location such as the base above it, before swapping so any new installation can be replicated by placing the pulley at the same distance from the base.

You got this!
 
Replaced the Briggs in my power washer with a HF Predator. Bolted right up. Bonus is the HF motor starts on 2nd/3rd pull every time. The Briggs engine was a 5-10 puller from brand new.
 
The last time I dealt with oil in it was lighter weight synthetic. The reasoning being it doesn't run long, though I have let it warm up a fair amount. I used along the lines of 5w-30 or so.
 
That looks identical to the 149cc Briggs 450 I have in my lawnmower. You can pick up an entire fuel tank & carb assembly very cheaply. I can't imagine much could go wrong with these.
 
A mower depends on inertia of the blade to act as additional flywheel. Make sure to get the "heavy flywheel" engine option for applications like this where there is no blade. Starting is otherwise difficult or impossible.

The bolt pattern on the base of the engine is very standard. There are three standard shaft diameters: 7/8 inch, 25 mm, and 1 inch. As others said if you're going to replace the pulley as well, it's not critical.
 
The small engine shop failed you. If it's solid otherwise and runs ok after a difficult start it's most likely a minor carb issue. Dirty or gummed up.
Maybe another shop or just drop the float bowl and go to town with a $2 can of carb cleaner.
It would be a crime against nature, considering you're in the great state of Wisconsin, to replace that sturdy old Briggs with a harbor fail engine.
 
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