# Generator Engine Swap 10hp to 16hp help?



## TheLastCrank (Oct 12, 2020)

Hello everyone. New here but not to small engine work. I need a little help and sorry if this has been asked. I couldn't find any info on this subject. I have a Briggs 5550/8550 max generator with a 10hp Briggs engine. I want to swap the engine to a Duramax 16hp or similar 420cc engine. The shaft size is fine but my concern is will the stronger engine affect the power output? I don't want to burn up the generator.


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## iowagold (Jan 22, 2020)

well as long as things bolt up.
you should be fine.

just set the gov to perfect.
i assume this is an standard avr style of head gen set.
as long as the engine rotation is the same.

*measure the shaft carefully.*

you will need meters for the hz setting under load and no load
59-61 hz 
it will depend on the gen head of how it loads up...

click here for the test equipment page
a killawatt meter works ok for the hz and voltage. and be able to look at watts as well.
(2) of the killawatt meters is a good idea for an avr setup so you could use ( 2) 1500 watt space heaters for a load one on L1 and a second on L2.


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## TheLastCrank (Oct 12, 2020)

Thanks. I dont know if it is AVR equipped or not. It probably is but I will try and look into it. The generator is 15 or so years old. Looking online the shafts are the same size just the Briggs is 2-29/32" long and the Dura is 2-3/4" long.


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## iowagold (Jan 22, 2020)

taper shaft?

snap a pix of the gen head


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## drmerdp (Apr 10, 2018)

Sounds like it wouldnt work. Unless... You fashion a 5/32" spacer for the housing to make up for the extra shaft length.


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## TheLastCrank (Oct 12, 2020)

@drmerdp I seen that but dont know how much of the shaft the generator sat on. @iowagold the Dura has straight shaft and from pics online the briggs shaft is only tapered near the end then it goes straight. Ill post some pics once I figure that out lol.


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## iowagold (Jan 22, 2020)

gens need the taper shaft.
it is the alignment.
as well as the direct coupling

the center bolt forces the gen head on to the cone shaft
and yes it needs to be 100 % perfect fit!!
it will eat bearings if it is not.


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## TheLastCrank (Oct 12, 2020)

Thanks @iowagold I am looking at other options as it looks like the Dura max wont work. I did find a Kolher 14hp Ch440-3119 that has a tapered shaft but wait to hear back on the dimensions of the shaft.


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## iowagold (Jan 22, 2020)

TheLastCrank said:


> Hello everyone. New here but not to small engine work. I need a little help and sorry if this has been asked. I couldn't find any info on this subject. I have a Briggs 5550/8550 max generator with a 10hp Briggs engine. I want to swap the engine to a Duramax 16hp or similar 420cc engine. The shaft size is fine but my concern is will the stronger engine affect the power output? I don't want to burn up the generator.


do you have the drawings for the old engine shaft??
you might contact briggs...
see if they have a late model replacement..
or at least drawings for the replacement engine mounting and shaft..

I would be looking at honda gx engines..
like a gx390. they are 11.7 hp and 390cc.
they do make them with taper shaft.
and they have both sae and metric models on the bolt up and taper.
the dimensions are at the bottom of the page under pto.
there are two pix one for the sae print and the other for the metric print.
click here for the gx honda factory site

message me if you need an online or local vendor for the honda engine.
northern tool also has them online.
click here for northern tool honda engines
they are more bucks...
but a gx honda engine is the best engine period!
and makes a real good gen setup if your power head is real good!

just watch your dimensions for the head mounts.
as well as the taper and thread on the id of the shaft.
you can check the oem bolt for the gen head center for that.


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