'98 115hp 2stroke Oil leak from spark plugs

[Jason2tpa]

Very true, I shouldn't assume. I'll check compression. Is it also a possibility a carb jet is clogged or float stuck? When I bought the boat/motor in Oct the previous owner said the carbs hadn't been cleaned or kit changed in a year. Could this cause the sudden loss of power?

[99yam40]

Compression, spark, and spark timing are all easily tested.
Fuel pressure is also testable

peak voltage into and out of CDI needs special test equipment(volt meter built for this type of ignition system or a DVA adapter with a regular meter.
Some motors have a low speed and high speed charge coil,but have no idea if yours does or not, or at what RPM it switches over from low to high.
Of course you motor could have a different ignition system and I am completely wrong

Timing is checked with a timing light just like an automobile motor.
If timing is not advancing to were it should be, RPM and power is affected.
Lack of enough fuel also will restrict power and RPM.

Trash or water can hit a carb at any time and cause problems

[TownsendsFJR1300]

As old as the engine is, varnish does tend to build up over time inside the carbs.

It certainly wouldn't hurt to pull the carbs and go thru them. Make sure you pull all the jets and can SEE THRU THEM. Checking for float sealing, proper height, etc.

You can also simply remove the bowl drain screws, catch what comes out and get an idea.


Also, IME, Seafoam works ok but Yamaha's RingFree works way better and would help keep your combustion chamber clean as well as the fuel system...

https://www.shopyamaha.com/product/d...?b=Search&d=34

[Jason2tpa]

Update: '98 115hp 2stroke Oil leak from spark plugs

Took the silencer off so I could visualize the carbs. As I was taking silencer off, I noticed in the top left a cylindrical shaped component with power wires. Come to learn this is the fuel enrichment valve. I wasn't familiar with it so I had a good look before completely removing silencer. Then I researched it and learned if left open this could drown the cylinders. There was a black plastic lever extending down from the FEV with a circle opening at the end. This opening lined up perfectly with a lever extending from the carbs choke, yet it was not attached. It was just hanging there. It looks as though there should be a cotter pin holding the FEV lever onto the carb choke lever, but there is not. I pushed the FEV lever onto the carb choke lever, then pulled the manual choke handle located on the bottom cowling. When pulling choke handle out, the carb choke lever pulls down as it should and this pulls down the FEV lever.

Launched boat and throttled up and down the channel, no loss of power. Stayed out on the water another couple hours, no loss of power at max rpms or at any other rpm.

So could the loss of power I experienced yesterday be related to the FEV? Perhaps because it was not attached to the choke lever it was activated by rough seas or something. The engine ran great today, which pleases me, though I'm a little uneasy not knowing if this definitely was the issue. There is supposed to be a cotter pin holding the FEV lever onto the choke lever, right?

[99yam40]

Post a complete motor model #.

I do not see this part on carb break downs I looked at

and I did not know they put a FEV on carbs with chokes

Rodbolt should know , if he can remember back that far

[zenoahphobic]

We have a footballer down under called FEV. He also was a bit loose up top and showed some the symptoms you described. He caused all sorts of problems and was a bit "rich" to take for some. So I think your disconnected FEV would have atleast added to your problem.

[Jason2tpa]

S115W '98

I have the manual for my model year and it lists a fuel enrichment valve.

[TownsendsFJR1300]

Can you post the full engine model # up?

The couple of carbs I saw for your year shows regular choke plates. The cylinder with wires is probably an electric choke solenoid. The lever is likely a manual over-ride (should the solenoid fail).

It sounds like the choke butterflys were staying mostly closed (it'd have to be probably close to hallways closed) to affect, for the most part, the top end.

As black /nasty as the plugs were, that plays into that.


In any case, seems the main issue has been found.

A pic or two of that area posted here would likely help if you can't pin it down exactly. It may just be a pressure fit and that plastic cracked over time..


That pic is too small to be helpful, here's the parts fisch. And it is a solenoid; part #19:
http://www.boats.net/parts/search/Ya...202/parts.html

Zoom in and make sure all the parts are there. There's also a spring(probably a return spring especially)

[Jason2tpa]

Townsend...you choose the correct model # from the parts fisch. I've attached the service manual page in pdf format. Hopefully it's larger for you to see. If you can, look at #6. Ironically, it's in the same position on the motor and looks the same as part #19 solenoid, except the service manual attachment call it a fuel enrichment valve. Also, what I was calling the FEV lever is the pull wire #20. And this is definitely missing #25 the O ring, which is I found in dangling. Let me know if you're not able to make my attachment large enough. Thanks for all your assistance.

[rodbolt17]

there is no FEV on the 115.
there is an electric solenoid with a plunger and the plunger arm is attached to the stup on the carb with an oring.
the manual override is that pull out knob at the lower stbd side .

[TownsendsFJR1300]

Townsend...you choose the correct model # from the parts fisch. I've attached the service manual page in pdf format. Hopefully it's larger for you to see. If you can, look at #6. Ironically, it's in the same position on the motor and looks the same as part #19 solenoid, except the service manual attachment call it a fuel enrichment valve. Also, what I was calling the FEV lever is the pull wire #20. And this is definitely missing #25 the O ring, which is I found in dangling. Let me know if you're not able to make my attachment large enough. Thanks for all your assistance.

Your welcome.

BTW, Yamaha isn't very consistent in its terminology, so you have to look past that term in your case...

#19 IS literally a solenoid that simply pulls the choke closed. Its definitely not a Valve.

I could open the PDF but the parts fisch (at least on my end) shows more, especially enlarging the pic.

Seems like the issue is figured out and you know what you need. She should run great now!

Safe boating!

[Jason2tpa]

Ok, just so Im clear of the function of this soleniod when it operating properly...when ignition key is push in start, the solenoid activates closing the choke. I assume once the engine starts and key is released the solenoid deactivates thereby opening choke. Sound right?

A few days ago when I experienced the power loss my guess is when starting motor and pushing key in the solenoid activated but because the O ring is missing the pull wire must of slipped off the carb choke leaving the solenoid choke closed. Hopefully this was the cause since its an easy remedy. Thanks again!

Your welcome.

BTW, Yamaha isn't very consistent in its terminology, so you have to look past that term in your case...

#19 IS literally a solenoid that simply pulls the choke closed. Its definitely not a Valve.

I could open the PDF but the parts fisch (at least on my end) shows more, especially enlarging the pic.

Seems like the issue is figured out and you know what you need. She should run great now!

Safe boating!

[boscoe99]

S115W '98

I have the manual for my model year and it lists a fuel enrichment valve.

What is the document number for your manual? It will begin with LIT-18626-

Methinks thou doth not play with the correct deck.

[99yam40]

or he found one of the Yamaha famous misprints

[TownsendsFJR1300]

If you simply leave the cowl off the engine, turn the key to run (don't start), then watch the solenoid when you push in the key/button. See if it activates(closes the butterflys-full choke).

In the "run mode" (and POSSIBLY WARMED UP) the choke should be wide open. Yours for what ever reason, is NOT.. Missing clip, spring, etc, but it should open fully..

Yamaha, from what I've learned here, doesn't do everything the same and one model can be very different from a similar HP model.

*Also guys, click on the link up above I posted. its shows butterfly carbs and the solenoid with it for the choke AND IT is listed as a valve(in the parts section)