1985 Yamaha 9.9SK

[909]

Just picked this up from a fisherman.

He trolled for 4 years. Before him it was his cousin's.

It sat in storage for well over a year before today.

Included in the purchase was the original prop, and 2 new props.

Felt bogged down & rich (100 to 1) .

But pulled decent numbers.

Here is a video going top speed:

Watch c5d2fn | Streamable

Watch this video on Streamable.

streamable.com

Seems slow right?

In comparison my 76 Evinrude :

Watch 20210805_194912_2_1 | Streamable

Watch "20210805_194912_2_1" on Streamable.

streamable.com

Revs higher right? Seems faster right?

How do I make my 1985 Yamaha rev higher, and go faster than my 1976 Evinrude ?

 

[909]

Bump

 

[CaptnKingfisher]

Ya could put the Yamaha in your truck and probably get her up to 70 or 80 mph

I'm not sure you're gonna be able to beat your Evinrude. Not cuz I think one is "better" than the other but because they are entirely different engines and 9.9 hp rating does not translate very easily into lbs of thrust. That being said, I support your effort to try to improve performance.

First thing id check out is verify the throttle plate is totally open when you move the throttle control full forward. If it's not, link and sync the carb.

You will probably skip this step (I would) but if you're being thorough about this then rebuild the carb. Use a kit with new gaskets, clean out everything thoroughly, don't just soak in carb cleaner, plenty of guides on YouTube how to do it right. And when your done the rebuild and the thing won't start don't call me.

While we're on the carb let's tune this thing properly. You need an accurate tachometer. I use my timing light or I've got an automotive multimeter that's got a tach function. You could also get a 'tiny tach' but imo they're an overpriced one-trick pony.

Use your tach to moniter rpm, and set idle rpm according to your service manual. Remember idle speed is to be set with the outboard in water, not on muffs. The best way I can describe the idle speed screw location is it presses against the throttle linkage on the carb. Note the rpms after youve adjusted to spec.

Next set idle mix. run the engine at idle and youre gonna be adjusting the idle air mix screw at the carb while monitoring the engine rpms. First turn the screw clockwise in small increments until rpms begin to drop due to a too lean condition. If they are dropping immediately as you turn the screw then you are already too lean. Next turn the screw counterclockwise slowly and you'll see rpms begin to rise at first, then as you continue turning rpms will begin to drop again due to a too rich condition. Now you've got a sense of your operating 'range'. Make your final adjustment by turning clockwise again in small increments adjusting for maximum rpms and engine smoothness. Now your idle mix is set correctly.

if your idle rpms are exactly where they were before you adjusted the mix, then the mix was ok to begin with. If the mix was bad, your rpms will have increased, and you should now use the idle speed screw to decrease the rpms back to spec. If the rpms are lower than when you started then you messed up, try setting the mix again.

While we're in the fuel system clean or replace your fuel filter. Then we'll move on to ignition.

Replace the spark plugs. There's no reason to do this but literally everyone here seems to do this anytime their engine does something they don't like. But really, pull the plugs, inspect em for wear or fouling, re gap the plugs (.028) and when you put em back, put some dielectric grease in the spark plug boot. Also verify the spark plugs are correct for your outboard .. NGK B7HS-10

Leave the damn coils alone, theyre fine.

Try some of your different props out. Props make a pretty significant difference to top end. I'm not sure anything I suggested will get ya goin any faster but nothing I suggested will hurt either. If you're looking for quick 'hacks' to gain speed, you won't find much.your best bet is trading in the 9.9 for a 15 hp. Exact same size and weight outboard but noticably faster.

 

[909]

Excellent post.

I'm going to do everything you mentioned.

Is the only difference between the 9.9 and the 15 the reed valve spacing and throttle limiter ?

 

[CaptnKingfisher]

Excellent post.

I'm going to do everything you mentioned.

Is the only difference between the 9.9 and the 15 the reed valve spacing and throttle limiter ?

It varies based on year but often the main (sometimes only) difference is the carburetor. Some people convert their 9.9s to 15 hps. Wonder if someone converted your old Evinrude before you got it.

While youre giving this thing some love, if the outboard is new to you it's a good idea to change the impeller and gear oil

 

[909]

It varies based on year but often the main (sometimes only) difference is the carburetor. Some people convert their 9.9s to 15 hps. Wonder if someone converted your old Evinrude before you got it.

While youre giving this thing some love, if the outboard is new to you it's a good idea to change the impeller and gear oil

I'll order the parts.

My Evinrude has the 9.9 carb, but he did swap the flywheel and converted it to from points & condensers to CDI . Does it make a big difference? What's the advantage ?

I also have a 15 Evinrude which goes a bit faster than the 9.9 Evinrude, but uses the older points and condensers.

 

[CaptnKingfisher]

I'll order the parts.

My Evinrude has the 9.9 carb, but he did swap the flywheel and converted it to from points & condensers to CDI . Does it make a big difference? What's the advantage ?

I also have a 15 Evinrude which goes a bit faster than the 9.9 Evinrude, but uses the older points and condensers.

I've read on this forum that an electronic ignition will never perform quite as well as points but the poster didn't support the statement with an explanation, though it was a pretty knowledgable regular on here so I believe the statement without having an explanation lol. I think the main reason people convert is cuz points need a little tlc once in awhilw and nowadays people don't know how to maintain points and don't wanna learn. But it's really simple I'm learning as I go. Electronic ignitions (good ones) don't need any maintenance but some of the ones out there have a reputation of being unreliable so you gotta do some research before converting

 

[boscoe99]

I've read on this forum that an electronic ignition will never perform quite as well as points but the poster didn't support the statement with an explanation, though it was a pretty knowledgable regular on here so I believe the statement without having an explanation lol. I think the main reason people convert is cuz points need a little tlc once in awhilw and nowadays people don't know how to maintain points and don't wanna learn. But it's really simple I'm learning as I go. Electronic ignitions (good ones) don't need any maintenance but some of the ones out there have a reputation of being unreliable so you gotta do some research before converting

It is quite amazing what one can read on the innerweb.

Mechanical points offer so much more performance that almost all new performance automobiles offer them instead of electronic points.

 

[CaptnKingfisher]

It is quite amazing what one can read on the innerweb.

Mechanical points offer so much more performance that almost all new performance automobiles offer them instead of electronic points.

Point taken but we're not comparing a modern ignition to an old one, we're talking about slapping a conversion kit on a rotor that was designed to operate a points ignition and comparing it to running with the points that it was designed to operate with. I'm not gonna try to support the argument tho, cuz I am a newbie still and don't have any sort of mastery over ignition systems

 

[99yam40]

points worked so well that even when you set them with a feeler gauge you still had to check and readjust with a dwell meter to get the set properly.
also had to replace them every year and maybe even more often if the cap went bad and caused the points to arc too much and pit.
not to mention the wear of the points rubbing block and the lobes on the distributor shaft

I never heard of the electronic set ups being a problem for may years

 

[909]

He's a good guy, and trying to help.

But is the difference between CDI and points significant enough to justify a swap.

 

[racerone]

Points are a cheaper system to own if you know how to maintain them , do the work yourself.----If you run to the $100 / HR shop for every little hiccup then electronic is the bestest way to go.

 

[909]

If there's no benefit , I'm not switching. No complaints. If it ain't broke...

If I ever paid another man $100 / per hour to fix my stuff someone please shoot me.

 

[Faztbullet]

That Yammy if set up correctly will perform better all around the Junkrude

 

[909]

That Yammy if set up correctly will perform better all around the Junkrude

I want to believe.


Check out this 9.9 to 15 conversion I found online. All he did was bend the reed valves to 6mm :

This is a 2006 engine, but as I understand it, the engine design didn't really change for about 20 years from mid nineties til a couple of years ago

The reed valves sit on a plate between the carb and the block, so to get at it you need to remove the carb. These 2 10mm bolts go through the plastic airbox (?) and the carb.

There were then various linkages between the throttle and choke mechanism. Most uncipped, but I found that I needed to undo this screw, which attaches the choke mechanism onto the side of the plastic airbox.

I also had to loosen this screw to slide this linkage out. I marked its position with a marker pen.

Once the linkage was loosened, I could rotate the carb to the side, without removing the fuel line. This revealed the reed valve plate

There are 3 10mm bolts holding on the reed valve plate.

This is the reed valve. Notice one side I have opened out and one is in the stock condition:

I had read of people opening the reed valve out with pliers, but I was worried of twisting it, or damaging the rest of the assembly, so I removed the plate and rigged up a bending fixture in my vice, using a bit of brass I found.

I needed something flat to bend out the clearance, and settled on a bolster chisel.

My feeler gauges don't go up to 6mm, so I measured various things in my toolbox til I found something that was right. (I've since heard of using a 6mm drill bit, which would have been easier!)

The second stage was the "rev limiter", this was a little tab, which stopped the throttle fully rotating. I was thinking about bending the tab, but didnt want to strain the mechanism. I also thought about remving it totally, but was worried that when I remved the bolt it would spring apart. Not sure what to do, I decided to losen the bolt slightly to see if I could rotate the tab. After a couple of turns, the tab just fell off - it turns out that its slotted. So this bit was very easy:

And that was that. I ran out of time, so I haven't fired her back up. I also received a tachometer in the post today, so I'll have that installed for when I fire the engine back up.