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by Douglas Keith

(Doug mentioned that he had used a Briggs in his boat, so I asked him to share how he did it since others have asked about converting smaller motors.)

Here we go…The tough question you asked is “how would I tell someone how to do this”. Boy, when I thought about it in those terms, I realized how hard this would be. Well, here goes.

First a summary: As for cooling, the Briggs I used was splashed lubricated, so I had to mount it on the horizontal, then come off with a jack shaft to a pillow block with a thrust bearing, then to a universal joint (I used a Spicer), then thru the floor through a 16 degree shaft log. In short, it kept the motor upright and in the relative wind. It is a small boat designed for a special purpose, coon hunting, or you could use it in back waters where wave action wouldn’t be a big deal i.e. sloughs, small lakes, etc. It gets excellent fuel usage and makes about 10 knots full bore. Transfer of power was done thru a centrifugal clutch w/double row chain to the jack shaft. I tried routing the exhaust out the transom, but it was too noisy, so I ended up with a straight up pipe w/muffler.

The details:

1. I used a Briggs model# 130202.

2. Overheating wasn’t a problem, in fact I never considered it. They are cooled with a fan, so it was never a thought.

3. I used a standard centrifugal type go-cart clutch w/double row chain. I found out by trial and error, that a single row works, but durability is not there.

4. After the clutch, down to a shaft with a sprocket, the one I used was held in place by 2 pillow blocks, fore and aft.

5. Then to a u-joint. You need one with strength, so I used a Spicer rated at 40hp.

6. Next a thrust bearing. This is where you get your shaft log angle, so the thrust bearing is mounted at the angle of the shaft log. In my case at 16%. I got the bearing from Kaman Bearings. It was adjustable, so I could mount it flat and then rotate it to match the angle I needed.

7. Then you go through the floor using a standard shaft log and packing gland then to the strut, and prop.