1996 yamaha 115 with rebuilt power head question

nasdaqsam

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The saga continues. There is some back ground to this motor but basically I received a lot of help here on the forums with it in the past. I ended up having a rebuilt power head put on it up here in NY. Tried it on the water a couple times and ironed out some kinks nothing major. It seemed to be running good so I shipped it to Florida. When it got there I tested it on the water there it was not running right. the best way I can describe it is that is was running as if it was built too tight.

I hired a local mechanic there to take a look at it. He found it to be running rich so he re jetted it but I was having a heck of time getting it started also and the batteries keep dying. The draw is coming straight from the engine with everything on the boat unhooked. He tested the electronics. He found the starter to be weak and the solenoid to be drawing a very low voltage continuous draw. I had both of these replaced.

So here is my question, I am not in the area right now and when I am I have very little time and resources if the boat breaks down on the water. (I do have seatow). The mechanic is saying it is running fine on the water ears but that has always been the case. Its when it is in the water under load. Is there anyway to run an engine under load on land? Or a way to simulate load?

Thanks
​Scott
 

99yam40

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Yamaha and others have test wheels for outboards.
Should be able to hit a certain RPM at WOT if motor is running properly
Yamaha shop should have them to run in a test tank or with boat tied on a trailer in the water
 

ondarvr

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Re-jetting sounds odd, and going leaner on a fresh rebuild would even be more unusual.

You may need to describe exactly what "built too tight" means.
 

nasdaqsam

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Yamaha and others have test wheels for outboards.
Should be able to hit a certain RPM at WOT if motor is running properly
Yamaha shop should have them to run in a test tank or with boat tied on a trailer in the water
I am going to have to have a Yamaha shop look at it if they have that kind of a setup. Thanks for the input.
 

nasdaqsam

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Re-jetting sounds odd, and going leaner on a fresh rebuild would even be more unusual.

You may need to describe exactly what "built too tight" means.
Hard to describe. But here goes. When I took it out, being a new build I took it real easy but was against the current. The engine felt tight like it was struggling to make rpm. Just from running this boat for the past 20 years I have a pretty good feel for how she used to run. With in a few minutes of climbing the rpm scale the over heat warning buzzer came on so I brought i back down to idle the buzzer went off. I put it in gear and continued slowly. It seemed to run ok at lower rpm's but was really struggling to make rpm if I tired to climb again. It did this against or with the current. A little less with the current. If I tried to make any rpm it just started running like it was flooding out or lacking gas since they both feel about the same I guess might be a better way to describe it. The mechanic re-jetted because the plugs were showing wet after running on the ears. Does that help?
 

ondarvr

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That sounds more like it's running lean, running rich normally results in a rough running smokey motor. Lean tends to be smooth, and maybe difficult to build power if too lean.

Trying to re-jet a motor from how the plugs look after running it on muffs is a huge mistake, this in no way represents how it will run in the water under load.
 
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nasdaqsam

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Yamaha and others have test wheels for outboards.
Should be able to hit a certain RPM at WOT if motor is running properly
Yamaha shop should have them to run in a test tank or with boat tied on a trailer in the water

​Does anyone know where I can get a test wheel and maybe a part number?
 

99yam40

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I would think a Yamaha dealer shop would have them, but not sure you could buy one from there,
 

nasdaqsam

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Never was able to locate a test wheel but finally made it down to Florida to test the boat out. I kept it low rpm mostly because being a holiday weekend the water ways were jammed packed. One of the original issues I had was when ever I tried to give it any power after about 5 minutes the over heat alarm would go off and it would run like crap. Once I backed off and lowered the rpm the alarm would turn off and it would run again. Not good but it would run. After all the work this mechanic did I will say it is running smooth but the same over heat happens after 5 minutes. It has a good stream of water but I am thinking the impeller has to be the issue. It must be getting enough water to keep the engine below temp when running low rpm but over heats when pushed. That's the next thing to test. It did run good up to 4800 rpms but that is all I could get out of her. She typically runs around 5000 to 5100. I am thinking this is the lower jetting he did. Couple of questions:

​1) Is my impeller thought plausible?

2) Going down one size on the jets is that 300 rpm's worth?

3) Would running in brackish water with current compared to running in fresh lake water effect the prop choice? Should I run a little less pitch?

Thanks
Scott
 
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99yam40

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I would be concerned about him rejetting.
was it the main jets?
lean will run hotter than it is designed to run and may cause motor damage.

was there a major altitude change ?

air at higher altitudes has less O2 available and needs to be rejected sometimes to run properly up there, but when running back a sea level it will be too lean

and with less fuel being burned there is less HP being produced, meaning a different prop would be needed up there too
 
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ondarvr

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There is no way to say what the leaner jetting will do, it's not an RPM related change, it may rev higher, or lower, or no chnage at all. The one thing it can do is destroy your motor, so stop running it until you figure out why he did it and what jets he put in. Having it run lean during a break in period would even be worse.
 

nasdaqsam

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I would be concerned about him rejetting.
was it the main jets?
lean will run hotter than it is designed to run and may cause motor damage.

was there a major altitude change ?

air at higher altitudes has less O2 available and needs to be rejected sometimes to run properly up there, but when running back a sea level it will be too lean

and with less fuel being burned there is less HP being produced, meaning a different prop would be needed up there too
​We went from Lake Champlain in upstate NY to New Smyrna Beach FL. so no real change in altitude.

I'm going to have him put the originals back in just to be safe.

Thanks for the reply
 

nasdaqsam

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There is no way to say what the leaner jetting will do, it's not an RPM related change, it may rev higher, or lower, or no chnage at all. The one thing it can do is destroy your motor, so stop running it until you figure out why he did it and what jets he put in. Having it run lean during a break in period would even be worse.

The plugs were running wet. He said in the Yamaha manual there are three sizes of recommended jets. He went from the riches to the middle set. I guess not a big change.

The thing is the boat ran really good for a long time just cruising. It was only when pushed a little it overheated. I really think that is the impeller but we will know for sure once we change it out. Then change the jets back will hopefully do the trick.
 

99yam40

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I guess it all depends on where you plan on running it.
if you keep going back and forth between the different elevations you probably need different props and jetting.

what is the elevation up there that you run it?

never mind my thoughts as it is only 100' different from sea level

Water pump kitand a housing if that shows any sign of melting.
along with stats and PRV would be a good start on cooling issues.

Did they give you a procedure to follow while breaking in the power head?
 
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ondarvr

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The plugs were running wet. He said in the Yamaha manual there are three sizes of recommended jets. He went from the riches to the middle set. I guess not a big change.

The problem is when running on muffs you would be on the low speed jets and with no load, this in no way represents what running in the water submerged to the correct depth and under load at high RPMs is like. So there's no way to tell if the jetting is right or not. And you said it ran correctly before, so until you get it broken in and running correctly there's no way to tell if it needs to be jetted leaner.
 

nasdaqsam

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I guess it all depends on where you plan on running it.
if you keep going back and forth between the different elevations you probably need different props and jetting.

what is the elevation up there that you run it?

never mind my thoughts as it is only 100' different from sea level

Water pump kitand a housing if that shows any sign of melting.
along with stats and PRV would be a good start on cooling issues.

Did they give you a procedure to follow while breaking in the power head?

​I plan to keep this one in Florida. When the impeller gets changed I will have it al checked to be sure. They didn't give a break in procedure other than to not keep it any one rpm for very long and don't max it for the first hour.

Thanks for the help
 

nasdaqsam

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The problem is when running on muffs you would be on the low speed jets and with no load, this in no way represents what running in the water submerged to the correct depth and under load at high RPMs is like. So there's no way to tell if the jetting is right or not. And you said it ran correctly before, so until you get it broken in and running correctly there's no way to tell if it needs to be jetted leaner.

I agree its night and day under load. I tried to find a test wheel but was unsuccessful. New they are quite expensive so for one test its a big expense. The last run out it was running about as good as it ever has until it wants to overheat that is.

Thanks
 

99yam40

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most break in's call for 2 x oil during breakin.

Yamaha shops usually have the test wheels to test the motors, as I said they probably do not sell them, just test with them.
It is a way to check a motor itself to make sure it can do what it is suppose to, separate from the hull or rigging problems
 
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nasdaqsam

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I don't really have the ability at this point to get it to a yamaha shop in the area as I am rarely there and when I am it is typically a weekend. Of the shops I did call I can drop it off but parking is at a premium so they want it gone after they work on it which is just not possible for me since it might be months before I get back down there. And it would be preferable it is running when I do get there so mobile marine is about my only choice right now.

With the break in they didn't ask for anything like that just take it easy for bit don't run it wide open for any length of time and vary the rpm's.

I'm going to start a new thread about the over heat issue and the procedure. Thanks for all the help I am a lot farther than I was with it.
 

nasdaqsam

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Diagnosing procedure for overheating on a 1996 115hp Yamaha

If you have been following my other thread on this motor I believe we have determined at least one issue which is; it runs great with no issues at low to mid rpm range but when I go to WOT for any length of time but typically 5 minutes or less the over heat alarm sounds and it goes into safety mode. Let is idle for a short bit and the alarm goes off and she comes out of safety and runs good again at low to mid rpm. To bring any new comers up to speed this is a fresh rebuilt power head. What would the procedure be to diagnose an over heat issue? The engine appears to have a good stream of water coming out.

We are going to pull the impeller to see what it looks like but it was changed when the power head was done. I know it doesn't take much to burn one up either. While it is torn down what else needs to be looked at? A parts diagram would be helpful. It was mentioned on the thread to look for signs of the plastic melting also. I am very unfamiliar with the cooling system on this engine.

Thanks.
 
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