new to Yamaha

[2MADAKAT]

Hi guys,<br /> I am the proud owner of a rebuilt 1990 115HP Yamaha. I have never owned a Yamaha before and have a couple of questions.<br />1. The current prop has a 21 pitch and I can only get 4500-4600 rpm out of the motor. Very slow in the hole. What pitch should I look at for<br />skiing, tubing and fishing? Shouldn't I be able to get 5500-5800 rpm out of motor?<br /><br />2. I had a problem with the alarm horn sounding in my remote control. Found out that I only had one sensor on one head. Would this have caused the problem with the horn? I had the oil injection disconnected but had to leave oil in the main resoirvoir to keep alarm off. Normal?<br /><br />3. I have a long black wire coming from CDI with a plastic cover over plug end that goes nowhere.<br />Any ideas? Could it be a guage wire? I only have a speedo, tach, and trim guage currently.<br /><br />I hate to sound stupid, but I would like to understand this motor better.<br /> Thanks.

 

[dcpcccrc]

Re: new to Yamaha

my yamaha has that prop on it with 21 pitch and come to think of it i would like to know the same thing. i only get 4800rpms out of my 115hp, it takes a while for it to pull me up on one ski but it will do it and even on a sterndrive v8 i dont pop right out of the water. you had to leave oil in the main tank because in both tanks there is float so if your buzzer is going off you can look at the tank on the side of your motor if it is full then the problem is in the tank below. if the buzzer was continuous then yes i think it would be the sensor a continuous buzzer is overheat anything else is oil

 

[huanca]

Re: new to Yamaha

prop size depends on engine AND load. You should be able to get 5500 WOT max. sounds like you should go down to 17". Are you running cupped of 4 bladed props?<br /><br />i would get a water pressure gage (0 to 30 psi) plus a temp gage (100 to 240 F), cheap and good insurance. <br /><br />i doubt the lack of sensor would create the problem, get the missing temp sensor and install it.<br /><br />if you disconnected the oil injection I assume you are running premix fuel, right? what ratio are you using?

 

[2MADAKAT]

Re: new to Yamaha

Been away for a week testing the boat. The horn is no longer sounding but two other things have come up.<br />First, I use a 50:1 mix for my oil. I am using quicksilver oil and the motor smokes like a chimney everytime I fire it up after stopping.<br />Engine is just rebuilt, compression is 140psi per cylinder.<br />Second, when I reach 3800rpm the motor starts to shake a little and starts dropping the rpm. I slow the throttle, drop into nuetral and start over again. As long as I don't go beyond 3800 rpm it runs beautifully.

 

[huanca]

Re: new to Yamaha

Just rebuilt engine, use 25:1 mix for the first 50 hours, smokey but cheap insurance so all metal parts wear just right.<br /><br />I dont know your engine but if it drops the rpms, maybe its internal computer is sensing something wrong and dropping them for you. The horn may be bad but the computer senses it overheating so it drops RPMs. It might justbe a fuel delivery problem, check your hoses and filters carefully.<br /><br />If you have more weight on the boat, engine may be working harder to get to 3800 than it was doing to get to 4500. Try to lighten the load and see where your RPMS reach.<br /><br />If it were my boat, I´d get the water pressure and water temp gage, literally, TODAY. In my case it has been the best insurance against damage AND best troubleshooting guide. It takes away the guessing game and the first hour of a mechanic to diagnose the problem will cost you more. If you have good water pressure 15 to 20 psi, temperature should be OK unless timing is way off, or inside passages and scaled badly or engine is grossly overpitched or overloaded. A water pessure gage will show if the water passages are clogged, if impeller or water pump are bad or slowly going bad or if poppet valve is bad. A temperature gage will show if engine is overheating that timing is way off, that the water passages are badly scaled with rust, if the boat is overpropped (which yours I think is).<br />I am not expert but have sound tecnical knowledge of engines and been through the same process and cannot emphasize the need for reliable information when troubleshooting. Good luck