Yamaha F115 power loss

[Mazanek]

I have 2000 F115 four strokes. One engine does not develope full power. Runs good at idle and lower end, but progressively lags the other motor as I throttle up. Changed plugs (old ones looked great), full filter. Seems as the engine is fuel starved, doesn't miss or smoke. Ran great for 400+ hours then this happened. Checked linkage and throttle fully opens at engine same as other.<br />Engines would run to about 5700 at full throttle now the one only gets to 4700 and drags the other down to about 5300.<br />Any suggestions would be greatly appreciated as its tough to get shop time this time of the year.

 

[jsnyder]

Re: Yamaha F115 power loss

The first thing I would check is the throttle linkage. Make sure the throttle is fully open upon full throttle. I have this same engine and I can see where the throttle cam could wear over time.

 

[rowbards]

Re: Yamaha F115 power loss

Have you checked the fuel pressure? Try primming the bulb while running?

 

[jim dozier]

Re: Yamaha F115 power loss

Do a compression check.

 

[Greengilz]

Re: Yamaha F115 power loss

I had similar symptoms to this but far more extreme. Both our motors gradually slowed to 3500 rpm. Turned out to be fuel blockage in the filters before the injector pump and in the injectors (dirty fuel). I didn't have a Racor prefilter fitted but kept the filter/water on the motors clean. Microscopic inspection showed particals as large as 100 micron blocking the injectors. EFI fuel injecton specilists I have been dealing with say EFI cars have pressure filter down to 5 micron just before the injector rail. Honda outboards appear to have an appropriate pressure filters but Yamaha don't seem to have learnt yet. We had our filters replaced, fuel system & injectors cleaned, and 2 micron Racor prefilters fitted. 200 hours later my motors were wore out with water & fuel in the engine oil. Turns out some particals left over afer the cleaning got into the injector(s)and then injectors leaked fuel into the cylinders and crankcase every time the motor was turned off. Remember it only takes 1 particle of dirt to do this. As the majority of my motor hours are trolling and I swap over motors frequently the fuel diluted the oil very rapidly over a 24 hour non-stop trip. The other issue which contributed to the motor wearing out was inadequate oil cook-off from all the slow speed trolling and emersion of the oil pan. The oil does not get hot enough to cook-off the normal combustion volatiles (including water). The water adds corrosion errosion wear to reduced oil viscosity wear. The motors also have blind cavities under the block which capture and hold the water vapour which turns to sludge. <br />I think my problems were caused by fuel filtration not suitable for the purpose intended and outboard not suitable for purpose intended.<br />No help from Yamaha in this part of the world so I will buy Honda next time.

 

[Mazanek]

Re: Yamaha F115 power loss

Grteengliz,<br /> Thanks a ton for the post. So if it is contaminated injectors, don't clean them, replace them? Yamaha would not cover this under warranty even though they don't provide adequete filtration and I had my engines dealer installed? The particles pass right through the engines fuel filter and get to the injectors. By coincidence (I hope) I just put about 8 hours trolling on the engine when I first noticed the power loss on the run home. Later oil change; oil seemed ok and didn't have any fuel smell or water look, so maybe it'll be OK with injector maintenance. Thanks again

 

[Greengilz]

Re: Yamaha F115 power loss

Mazanek,<br />When we initially had problems Yamaha NZ said the injectors carn't be cleaned and they only had 2 in the country. No offer to import more. We needed 8 injectors so we made some equipment to back flush them, test shut off and spray patterns. The equipment worked realy well for removing the crap out of the injectors that the standard F115 filters let through. The second time we paid professional injector cleaners as we wanted an independant report incase we took the matter further. They removed the inlet baskets, ultrasonic cleaned them as well as measuring the continuous and pulse flow rates. The cost was 1/10th of the cost of new injectors. Yamaha NZ now say the injector manufacture does not recommend cleaning the injectors. The injectors are made by Denso under licence to Bosch. Denso won't tell flow specification, impedance, resistance, recommended filtration levels or any other good to know stuff as they bound by a OEM confidenciality agreement. Yamaha won't tell because they want to sell you new injectors. I would get the professionals to clean mine again if it was me. Bosch recommend and say it is common practice to cleaning EFI injectors. (not mechanical injectors tho). If it is contaminated injectors make sure your motor tech makes a really, really, really, really good job of cleaning the fuel system especially the pressure regulator. Or even better, fit a pressure filter before the injector rail. http://www.cantonracingproducts.com/pr_25907.htm looks like a particularly good one. I have trouble smelling petrol in the oil at lower levels but a good trick is to spread a few drops from the dip stick onto some coffee filter paper - makes a big difference. Remember the first instruction in the Yamaha maintenance manual when changing the engine oil is "CHECK FOR GAS IN THE OIL"