1996 Yamaha 115 Saltwater 2 Stroke S115TXRU no power, loss of RPMs

[jsalty]

1996 Yamaha 115 Saltwater 2 Stroke S115TXRU

I am having an issue with my 115 at full throttle, the engine dies or starts to die till I let off the throttle or if I don't catch it in time it will not recover resulting in a stall.

also just Friday the 115 would not produce more than 4,000 RPM when placed in full throttle forward until it was there for a few minutes then she took off and died as I did not back off the throttle.

I have replaced the fuel system and cleaned the carbs, yet the problem still exists.

any help would be appriciated, I have the boat home this week to fix.

thank you all for your expert opinions and advice, in advance.

Jim

 

[99yam40]

Re: 1996 Yamaha 115 Saltwater 2 Stroke S115TXRU no power, loss of RPMs

monitor fuel pressure and vacuum to make sure supply if good.

what does "I have replaced the fuel system" mean?

 

[jsalty]

Re: 1996 Yamaha 115 Saltwater 2 Stroke S115TXRU no power, loss of RPMs

monitor fuel pressure and vacuum to make sure supply if good.

what does "I have replaced the fuel system" mean?

Fuel lines from tank to carbs, including in-tank pickup, water separator, primer bulb, on engine filter and on engine fuel pump.... no other parts to replace other than carbs.

I was thinking I may have a reed issue or compression problem, I am going to pull the reeds and measure gap, plus check general condition, perform a compression test on all 4 cylinders.. How would I check vacuum, while running down the river or under no load in the driveway?

Thanks again?

 

[99yam40]

Re: 1996 Yamaha 115 Saltwater 2 Stroke S115TXRU no power, loss of RPMs

both to make sure there is no restriction
But need to look at it when problem shows up for sure
http://forums.iboats.com/showthread.php?t=283363

It is either loosing fuel/sucking air or spark, I do not think reeds would have anything to do with it.
Compression is always the 1st thing to check when having problems
Spark can be checked with timing light on the different plug wires and you can also see if timing is staying advanced while at it

 

[jsalty]

Re: 1996 Yamaha 115 Saltwater 2 Stroke S115TXRU no power, loss of RPMs

If I idle around for a while the engine will not produce RPMs and just bogges out quicker.. if I let her rest she will come to life.. Perhaps I have an in-leak to the fuel lines somewhere. Going to give her a good once over tonight.

 

[jsalty]

Re: 1996 Yamaha 115 Saltwater 2 Stroke S115TXRU no power, loss of RPMs

carbs cleaned, the pilot jets were turned out almost 1 turn when they shoud be 5/8s of a turn out. No dirt or varnish, I did adjust the floats to 16mm as they were all higher than that by a mm or more, this should allow more fuel in the bowl but a WOT it should not matter much as the floats would be open the entire time.

spark working fine, not sure about timing advance, will read a bit on that and fire her up tomarrow. plugs look in good condition I still plan to replace them after I use a can of 'yamaha power tune'

Compression is about 135-140psig on all 4 pistons, this should be fine if my math is correct from BAR conversion.

I plan to toss a fuel pump on as the last one was replaced in July 2010 and the problem has been going since then.

any other thoughts? maybe a 25 foot pro line with twin 130 4 strokes would fix my issue..

 

[99yam40]

Re: 1996 Yamaha 115 Saltwater 2 Stroke S115TXRU no power, loss of RPMs

Is there a reason you refuse to test fuel system like I mentioned?

Need to be testing even spark at problem RPM

 

[jsalty]

Re: 1996 Yamaha 115 Saltwater 2 Stroke S115TXRU no power, loss of RPMs

I have not refused to check the fuel system like you mentioned.. i forgot to mention the checks i have done in my above post.

I checked the boat side fuel system, no leaks, holds 10lbs for 15 minutes before i released. from tank to engine filter.
I will check engine side today when i have it running, will check spark also at RPM.

can't check engine running as the carbs and plugs are still out, ran out of daylight and was getting late.. I start work at 0500...