6 HP briggs & Stratton outboard conversion

Hi,

I finished my weedeater conversion utilizing a Honda GX35NTS3 and this will be my second conversion project.

A friend of mine gave me an old Chrysler 62HD outboard that had a bad power unit. It also has forward, neutral and reverse. He had converted it to propulsion via an electric tread mill motor. I got what was left after he took the parts he wanted. I also have a 6HP Briggs and Stratton engine that was removed from a pressure washer that has the heavy flywheel. Looked here on the forum for ideas and also looked at a bunch of You Tube videos for ideas.

Have some spare time so I decided to give the conversion a try.

I completely disassembled the outboard. It had been painted several times and the paint was in bad shape. I put all the external housing pieces in my bead blast cabinet and removed the paint. Cleaned all the bolts and cleaned all the tapped holes in the housing for easy re-assembly. Those parts will be primed and painted prior to final assembly.

Yesterday, I made 4 stand offs and an intermediate plate made of 1.000 thick UHMW to support the B&S motor and its 3 stand offs. All of the stand offs are drilled and tapped with a 5/16 X 18 thread on both ends for easy installation. The stand offs are made from 1.000 O.D. 6061T6 Aluminum.

My friend gave me a love joy coupling for use with the project. One end of the coupling utilized the lower end of the original engine crankshaft that had the necessary female spline to attach to the the outboard driveshaft. The other end of the love joy coupling needs to be replaced with a larger diameter hole that will adapter the to the B&S crankshaft. I will try and locate one of those next week.

I still have to locate the 4 bolt holes for mounting the bottom plate to the stand offs and the 3 holes for mounting the motor stand offs to the UHMW plate that supports the love joy coupling. I think I will make some pointed 5/16 X 18 threaded inserts that I can screw down into the stand offs and let them protrude slightly from surface and then tap lightly on the plate to mark the holes. I used to have some of these that were commercially made but they have parted company somewhere along the way.

The original Chrysler outboard was a long shaft but I removed the lower housing extension to make it a short shaft. I will also need to shorten the forward, neutral and reverse rod.

So far, it has been a fun project and hope it turns out O.K.

I have attached some pictures that will give you an idea of what I am doing.

John

 

More Pictures

Hi,

Here is the second group of pictures.

John

 

Briggs convesion

Hi John

Looks like an interesting project. If you haven't already take a look at my thread 11 horse Briggs outboard conversion also take a look at my thread. A boat a motor and a trailer under Boat building. You can see my Briggs conversion in action on the Mississippi. Sounds like your doing it pretty much the same way. The only problems I found were the Briggs are noisy I would suggest running the exhaust under water. I also used a Chrysler outboard it was a 12.9 horse but the prop was still too small for the Briggs RPM. There's a free program from Castle Marine that can tell you real close what prop you need. What horsepower was the Chrysler outboard you used ? Let me know how it works out.

Dave T

 

Chrysler Outboard Horsepower

Hi Dave,

I followed your thread with great interest and used a lot of your ideas. Thanks for posting as it was a great help.

The Chrysler Outboard donor motor that I used was formerly a 6 HP rated at 5000 rpm. My first step is to get it running. I picked up the .875 ID Lovejoy coupling end this morning that will adapt the Briggs 6HP pressure washer motor to the drive shaft of the Chrysler donor outboard.

The prop shaft seal was also leaking and while I was at the Lovejoy dealer I picked up a new double lip seal.

I also picked up some gear lube and a pump for installing the gear lube into the lower unit. I just filled the lower unit and so far it seems to be leak free.

I also ordered some HEIMANN 5/16 X 18 TRANSFER SCREWS for use in aligning the standoffs on both the lower plate and the briggs power head. It may take a few days to get them and finish the drive shaft alignment.

I still have to make a new shorten FNR upper shaft as I removed the intermediate housing that adapted the original Chrysler unit to a long shaft version.

As the original Chrysler was rated for 5000 rpm and the Briggs is rated at 3600 rpm it may be a little short on power with the current prop. Not sure if there are other props that may fit the splines on my prop shaft.

Just a little fun project.

John

 

Throttle Control

Hi,

Anyone out there have any advise on throttle control for my 6 HP B&S pressure washer engine shown above? Any pictures and or part numbers would be greatly appreciated. Some of the original parts for throttle control via the twist handle on the Chrysler 6 HP motor are missing so hooking up to the original handle may not be an option.

The original throttle control arrangement on the B&S 6HP has several bell cranks and a lot of slop in the linkage and is very stiff and not easy to maintain good throttle control via an OEM lawn mower cable. I will try to take a picture of the current throttle arrangement today so you can see what I am talking about.

I may ?????? even replace the OEM throttle handle as one of the parts on the handle is broken.

John

 

Throttle Control Pictures

I have attached a few pictures of the current throttle control.

John

 

Current Progress

I was able to find a new double lipped seal for the prop shaft and install the proper gear lube with no leaks. I also installed the .875 LoveJoy coupling end on the B&S engine.

I primed most of the parts for the Chrysler 6HP outboard housing and made a new shorter FNR shaft. I am now able to easily shift gears and have a neutral.

Once my 5/16 X 18 transfer screws arrive I will be able to properly align and install the intermediate plate and stand offs for the B&S 6HP motor.

Getting close, hopefully I will have it finished within the next week.

Attached are a few pictures of the primed Chrysler 6HP housing.

John

 

Video Progress Update

Hi,

Here is a link to a video to show you the progress I have made.

http://www.youtube.com/watch?v=gvBxXWnO8mw

John

 

Briggs convesion

Hi John

Watched your video looks like you got it just about ready for water. Let us know how she works. If I were you I'd run the exhaust underwater. Mine was real noisy and I found when running upstream with a tail wind I had a problem with exhaust fumes blowing into the boat real bad. You'll probably need a bigger prop to use all the Briggs power you could probably go to a three blade and still clear the cavitation plate.

Dave T

 

Briggs convesion

Hi again John

A guy on this forum [hoytedow] has a couple of 8" three blade Chrysler props for sale. He offered them to me but they are the same diameter as the prop I have. Might be just what you need for a 6 horse Briggs though.

Dave T

 

Exhaust System

Hi Dave,

I just finished the exhaust header for the Chrysler 6.0 Conversion. It mates with the exhaust port on the Briggs and Stratton 6.0 HP engine. It is 3/4" pipe thread with a close nipple and 90 degree elbow. Then I intend to use a copper 3/4" Male thread to a 3/4" copper sweat fitting. I will have my friend silver solder that fitting to a piece of 3/4" soft copper pipe that I will fit to the lower housing of the Chrysler outboard lower unit below the water line.

Hopefully, that will quite the engine some and get rid of the exhaust fumes. I have attached a few pictures of the exhaust manifold for your amusement.


John

 

Chrysler props with ten splines:

 

Props

Hi Hoyt,

I just checked my prop and it is marked 8/3.

I measured the cross section of the splines and it was about .500.

The prop has 2 blades and 9 splines.

The thickness of the prop front to rear is 2.060.

Guess, the 15 hp prop shaft is different than the 6 HP.

Thanks for looking.

John

 

U R wlcm.

 

Briggs convesion

John

I'd go ahead and try the 2 blade prop. As soon as I can get time I'll check the splines and shaft diameter on my 12.9. Maybe if it will fit your motor we could make a trade, I could make a 4 blade from your 2 blade. Can you tell me the gear reduction on your motor I'll run it on the Castle Marine program with 6 horse at 3600 RPM and see what pitch and diameter prop it recommends. Running the exhaust under water should make it quiet, regular outboards are real noisy when you run them out of water.

Dave T