Retrofitting 6.75hp Briggs To Sea King Lower

[YOSHIBG]

Hello All, This Is My First Post, Hope It Works Ok. I Have An Old 7 Hp Montgomery Wards Sea King That The Powerhead Is Bad. I Want To Replace It With A 6.75hp Briggs Vertical I Have. I Hope Someone Can Help Guide Me. How Would I Hook Up Some Sort Of Centrifugal Clutch Between The Shafts So As To Not Be Direct Driven? It Appeares My Only Option Is To Have One Custom Made For $150.00, Which Defeats The Purpose. Any Help Would Be Appreciated...
Thanks

[alan white]

If you can put a pulley on the prop shaft down, and one on the engine, offset by a couple of inches, you could have an idler pulley with a lever (pulley inside the belt, not outside, otherwise can't have shafts close enough).
use a spring to force the idler into neutral, and a notch in the lever to catch a detent and hold in forward. Make detent adjustable.
The belt will act as a clutch, will cost a few dollars, pulleys won't be much either, will allow different ratios to be tried out (Briggs will be higher torque, lower RPM than original).
I picture a pair of plates, 1/4"-3/8" aluminum, one to mount to engine, one to lower unit, with maybe an inch and a half between them, spacers between with bolts inside them holding the plates on. The pulleys and idler go between, with idler pivot and arm also between. All drill press and table saw work, and maybe a couple of square feet of aluminum.

[YOSHIBG]

What About The Same Setup But With Some Sort Of Centrifugal Clutch (say Off A Go-cart Set Up)? Would That Work? How Would I Know About What Rpm's The Clutch Engaged?

[alan white]

The clutch will work of course, and without the idler, it's simpler. Can you save the one it had? RPM is what engages the clutch, regardless of power. Chain can be used (but a belt is cleaner). The clutch of any four stroke Briggs should be based on 3600 RPM governed redline. Your engine will accept any clutch with (is this right?) a 3/4" shaft that came off a 4 stroke flathead and possibly some OHV models (though I think they go higher--- but still should work.
You can change the springs in the clutch too, easily.
Those clutches must engage at around 1000 RPM, just a guess. Disadvantage against idler/belt is you can't putt-putt, which gives amazing fuel economy and surprising speed depending on hull type.
Another issue is the prop, which is designed for higher RPMs, maybe 5000?
Rather than change it, figure the difference between the designed RPM and the 3600 of the Briggs. My guess is you want to speed it up by at least 1.5.

[TerryKing]

... I Have An Old 7 Hp Montgomery Wards Sea King That The Powerhead Is Bad. I Want To Replace It With A 6.75hp Briggs Vertical I Have. .

Alan has given you some good perspective...

Question: What did the original engine have??? Forward-neutral-reverse, or just "start and Run"??

[YOSHIBG]

Only Forward, And Some Sort Of Inline Clutch, That Doesn't Work Anymore. To Be Completely Honest, It Never Ran For Me, It May Have Been Direct Driven. I'm Thinking Of Going The Centrifugal Clutch Route, Belt Driven - Only Now I Have To Determine What Size Pulley To Put On The Lower Unit Shaft To Have The Correct Ratio. This Is Confusing For Me.

[YOSHIBG]

It Had Forward And Neutral, To Put It In Forward, Had To Pull A Lever, That Apparently Engaged It Into Forward Somehow...does This Help? Clinton Engine Model # K7002107a

[alan white]

No kidding--- a Clinton. There's an old name. Clinton made a lot of two cycle engines way back. The lower unit pulley might want to be half the size of the engine pulley. I used to rebuild them as a teen and run them on all kinds of contraptions.
There will be someone here who is good with props. The prop should be marked with two numbers. find the numbers and hen see how many turns of the lower unit shaft equal one turn of the prop. With that, and the 3600 RPM engine max, we should arrive at the right pulley sizes.

[TerryKing]

It Had Forward And Neutral, To Put It In Forward, Had To Pull A Lever, That Apparently Engaged It Into Forward Somehow...does This Help? Clinton Engine Model # K7002107a

So it had a 'clutch', probably a typical outboard 'dog clutch' which is OK because of the propeller slip.

So maybe you don't NEED a clutch, especially as you can probably idle even lower than the original....

[YOSHIBG]

If So I Can Post A Pic Of The "clutch" And Let You Guys See It...

[alan white]

True, if there's a clutch, it might be functional. However, once the ratio is changed to speed up the lower unit shaft, the clutch will again work at the same speed--- that is if you increase the speed by pulleys, which makes sense given a two cycle is a much higher RPM engine than a four cycle.
I'm imagining a dog clutch now, never having seen one. I imagine two arms held in by springs on fixed pivots. The end of each arm has a semi-circular knob that goes outward at a certain threshold RPM. Around this, a drum has a scalloped inner surface. There is also a rubber damper built in between two parts that interlock like a typical shaft coupler. The rubber takes up the shock of engagement enough to soft-start the shaft to the prop.

[YOSHIBG]

Of The Clutch - I Think It's Not As Complicated As Some May Thing. Really, It May Just Be A Shaft Adapter...

[YOSHIBG]

Oh, I Forgot To Add. There Are No Numbers On The Prop - But 1 1/2 Turns On The Shaft Equals One Turn Of The Prop

[alan white]

Not what I expected. A shaft coupling wouldn't have a square hole in the side with what looks like a nub with a shiny surface inside.. Must be a very simple clutch, but looks a bit dry/corroded. Should be self-explanatory, once free and lubed.

where's Terry?

[YOSHIBG]

About This "clutch". If You Try To Spin It Counter Clockwise, Holding The Top And Bottom, Only The Top Spins. Clockwise, The Entire Thing Spins, Which Is The Correct Direction To Go Forward. The Little Nub, I Don't Know What That Is, I Want To Take It Apart, But Can't Figure Out How Without Tearing It Up. Some One With Some Knowledge Of The Montgomery Ward Sea Kings Would Be Very Helpful.

[alan white]

Yeah, that's a clutch. Very simple, but as said by Terry, props offer little startup resistence. The long shaft down must torque around like a torsion bar too to take up the load. Are you aware of the relative rotation directions of the two engines? The Briggs will be clockwise viewed from shaft output, and all you need to do is to look at the prop to know what direction the engine should go.

Any case, a soaking in kerosene wouldn't hurt, and blow out clean and dry, then grease. That aluminum looks pretty eaten up, by the way. Maybe someone here knows how to seal it while you're at it.

[YOSHIBG]

Yes, I Checked And The Rotations Are The Same...do You Think This Clutch Is Rpm Engaged? I Recall There Was A Lever You Would Pull To Put It Into Forward. Is There A Way To Take It Apart And Clean It? If It Would Work For Me, Then That Would Save $$ And All I Would Have To Do Is The Pulley Set Up

[alan white]

Right. There is a relationship between the clutch and the lever. So the relationship is through an increase in RPM unless the lever also mechanically effects the clutch (by raising or lowering a sleeve around the clutch and causing a part of the clutch to be thus effected, for example).
Again, common sense will apply. Any lever that would effect the clutch would be beefy and have a decent sized hole for the attachment of a rod.
Or, if centrifugal, there would only be a small hole for a light rod to the carburator only. And that thin rod or mechanism must now be altered to make the new engine do the same thing as the old one. The choke is easier, since the old cover won't fit now.
You really should be able to play with the clutch and maybe hook a drill up to it while its on the lower unit, COUNTERCLOCKWISE because you're looking backwards at it, meaning run the drill (hopefully a 1750 RPM reversing drill, plug in type) in reverse.
Do you still have the old engine and paraphenalia?

[YOSHIBG]

ok, if you pick the engine up and hold it over your head, looking at the shaft, then it is counterclockwise. But looking down at the shaft going to the propeller, it needs to spin clockwise to spin the propeller the correct direction. does this sound correct? I took the old "clutch" apart and it's gone. basically rusted through, then I broke it worse taking it apart. So that being said, what kind of go cart belt clutch should i but. the shaft is 7/8" by the way. also, i am kinda worried about when the clutch kicks in, it putting too much torque on the shaft and propeller getting them started.

[alan white]

It sounds correct. Seems almost all lawnmower type engines are CCW.
You should mount the clutch on the engine, so either 3/4" or 7/8" is my guess of the diameter, so long as it's a straight shaft and not tapered with a threaded end. Either that or find a replacement for the original clutch.
The clutch, if a common centrifugal one, has to have a pulley and not a sprocket, and while go-carts usually use chains, many kinds of power equipment use belts, so look into getting a replacement clutch for a piece of power equipment that uses the engine you have. Briggs makes an outboard line too, and perhaps something they use will work, don't know.
The lower unit shaft is another story. It would be wise if you could re-use the part of the broken clutch that connects to the lower unit shaft, if sound.
Then you have to adapt that to a common 5/8" jackshaft. If the original lower case shaft used the engine to carry the upper end of the shaft, meaning no bearing is at the top of the lower case inside, it will be easier, because the jackshaft will align the LC shaft with a solid connection. If an inside bearing is there, it will require a soft fit to the jackshaft so as not to stress it. What is needed then is a rubber-isolation type coupling, something used a lot between electric motors and pumps when inline.
The lower half of the rubber damped coupling would have to sleeve around a 5/8" section of shafting that is welded to the top of the clutch part that fits the LC shaft. So what you'd see before adding the mounting plates would be a stump of 5/8" shaft sticking out a couple of inches--- enough to slip the lower half of the isolation coupling down onto it. It can be below the lower mounting plate by a little bit, because the "jackshaft" can have bearings mounted on each of two plates and also pass through the bottom plate a little ways, enough to almost meet the shaft coming up (1/4--1/2" inch clearance is fine). So the clutch, belt, and pulley are all sandwiched between two thick aluminum plates. The "jackshaft" is coaxial to the LC shaft.
All that's left is to tension the belt, and I suggest the idler be a big 1/2" wide ball bearing outside of the belt. That would need an arm of 1/2"x 1 1/2" steel and a shaft stub welded to the flat of one end, and a hole in the shaft for a cotter pin near the top of the stub shaft. Its length would allow it to swing against the side of the belt on a bolt pivot, and a spring to hook the arm to pull it inward.

[YOSHIBG]

i think i'll look farther into finding a clutch now...when i finish i'll post pictures. any one else care to give two cents?

[Capt-Ron]

I do believe that the item pictured is a spring loaded shock absorbing adapter. I've run and worked on a few of this size/year motor and most were direct drive.

Good Luck,
Capt-Ron

[ben2go]

I know I'm bringing up an old thread.There is a big rpm issue with this.The original 2 stroke rpm were between 5000 and 7000 rpm.The new engine spins 3600 rpm max.The prop will turn at half it's rated speed.It not very effiecent but it will work.Stepping up the rpm through gears or pulleys would help.If the unit had a forward/neutral/reverse lower unit a clutch would be counter productive.The lower unit will need to be spinning in order for gears to mesh while shifting.If it's a direct drive,then a clutch would be a lot of help at start up and during idle.Just remember that slow speed operation may be reduced.

[ned L]

Again, yes the topic is getting old.... That is a clutch. The way it works is that there is a coil spring inside the metal shell , the spring nautally has an inside diameter smaller than the upper & lower shafts so that it couples the shafts together, making both shafts turn together, and the torque from the engine tightens the spring even more (a bit like how 'Chinese handcuffs' work on your fingers). When you want to go into neutral the shift lever has a pawl which come into line with that small square end of the coil sping (visible in the picture) and forces the spring to stop spinning, and at the same time forces the spring to open up in diameter enough so that it no longer grabs onto the shafts, allowing the crank shaft to turn while the prop shaft doesn't turn.

[pistnbroke]

the trick with all these engine conversions is to take the crankshaft out of the old engine and cut the end off with the mating spline...you weld or collar this to the new engine crank and that mates the two together...then you need spacers to positon the engine in place atop the old outboard

[ehuntersullivan]

hello i have a non running old sea king motor and lower end it is complete i bought it from a garage sale guessing i can make it work
but if it would serve you better then let me know
ehuntersullivan@yahoo.com

[ben2go]

You can make a plate and adapter to mount a small push mower engine in place of the power head.

[pistnbroke]

Thanks ehuntersullivan but I think you did not spot I was in australia !!!
We got lots of old motors here ....if you are adding a lawnmower motor then
1/ ensure you have the end of the engine crankshaft with the internal spline to make your adaptor from. Make the adaptor to the drive shaft first and then with the motor balaced on the top take measurements for the plate or spacers .. If you dont use a splined adaptor then you cannot lift the motor off.
2/ make sure it has FNR gears and a 3..75 B & S drives a 8 x7.5 fine


Photo is of a 4hp suzuki I adapted ..sorry the photo is the wrong way