Yamaha 85HP Losing Power Intermittenly

majorgator

Recruit
Joined
Aug 1, 2011
Messages
3
Hello All, I'm new to the forum but searching for a place to help me diagnose some issues with my motor.

I have a 1995 C85 Yamaha Outboard. I purchased it about a 1 1/2 years ago, but it sat on a shelf until a couple of months ago at which time I put it on my boat. Since installing it, I've performed some basic maintenance tasks: cleaned the carbs, replace thermostat and gasket, replace water pump and housing, changed the foot oil, replace spark plugs, and replace in-line fuel filter. On my list of things to do is replace the head gasket, which is leaking a little bit of water along the edge in one spot between the upper and middle cylinder.

However, the motor just loses power spontaneously, then regains power (most of the time) by simply restarting the engine and revving it up. For example, yesterday, we would be cruising along nicely when it would just lose nearly all power and start to shake terribly. When I try to rev it in neutral, it goes up very little and shakes. In this case, simply restarting the engine and revving it in neutral usually does the trick. Sometimes, when I'm trying to get underway, it just simply lacks any power. In those cases, it may operating with little power, then spontaneously gain power, then lose, then gain, etc.

My first inclination is that this is a power (electrical) issue. I'm pretty mechanically inclined, but when it comes to electrical matters of this nature, I don't do so well because its just so difficult to nail down the problem.

As an additional note, the fuel tank is new (and clean), new fuel/water separator & assembly, new fuel line and connections, and new primer bulb.

I welcome any thoughts on what might be causing these problems. I just think its electrical, but I may be dead wrong. Anyone else with any experience like this? Thanks in advance for your comments.

seth
 
Joined
Jun 25, 2011
Messages
12
Re: Yamaha 85HP Losing Power Intermittenly

When it does this how is the fuel bulb? If it is not firm and collapses you have something restricting fuel flow. I had the exact same issue on my 225. Fuel filter was good, new water separator, new fuel tank and fuel lines. But would do what yours was doing. turned out I my anti-siphon value and some junk stuck in it and was partially blocking/getting that ball stuck. $9.00 for a new one and zero issue! Have someone pump the bulb, it will not stay firm and collapses and will not pump back up you have a fuel flow issue,,,also check that your not vapor locking??
 

majorgator

Recruit
Joined
Aug 1, 2011
Messages
3
Re: Yamaha 85HP Losing Power Intermittenly

Thanks for the reply. I hadn't thought about checking the fuel bulb while underway. At one point when I was stopped, I checked it and it appeared normal at the time. Vapor lock is not an issue, as the tank is properly vented. I made sure of that.

seth
 

majorgator

Recruit
Joined
Aug 1, 2011
Messages
3
Re: Yamaha 85HP Losing Power Intermittenly

I went ahead and ordered the new fuel bulb, along with some new gaskets and components for the fuel pump. I'm going to try to stab away at any of the potential fuel solutions before messing with the electronics. I just learned that its possible to test the coils with a voltmeter. Has anyone ever attempted this?

seth
 
Top