Yamaha 115 loss of power

[Anthony Mattera]

I have a 91 115 yamaha.After being on plane at 3800 - 4300 RPMs for about 10 minutes an alarm comes on and causes the engine to lose RPMs.The engine is pumping a good stream of cold water and the oil injection system is working fine. After putting it in neutral and floating for a minute or two the alarm goes off and I am able to get back up on plane with full power.This continues to occur after another 10 or 15 minutes of running on plane. Has anyone experienced this and have any ideas on what I could possibly look for.I appreciate any help I can get.

 

[rodbolt]

Re: Yamaha 115 loss of power

hello<br /> first a complete tune up of the cooling system is in order. the tell tale water on this engine is picked off at the water entrance to the motor. it will be cold even if the powerhead melts down like chernobyl. then a check of the oil related components. you dont say if you have any visual indicators such as the lights or bars on the tach face.<br /> check the filter in the remote oil tank if its clogged it will give symptoms of run then alarm due to the restriction slows oil transfer to a point that at high speed the oil is used from the engine tank faster than the transfer can be made from the remote tank. if all of the above fail remove the cyl heads and clean out the cooling system passages. your symptoms are also classic head gasket leaking combustion gas into the cooling system. while the heads are off check them carefully for flatness or send them to the machine shop for a quick surfacing.<br /> good luck and keep posting

 

[Anthony Mattera]

Re: Yamaha 115 loss of power

Thanks,Rodbolt I will check each of your suggestions and let you know what I found.

 

[Anthony Mattera]

Re: Yamaha 115 loss of power

rodbolt<br />I removed the oil tank and cleaned everything and reinstalled it and bled it for air.I experienced the same problem so I ran the boat with the engine cover removed and when the alarm sounded I let the motor idle in neutral and felt the cylinder heads. They were hot but not so hot that I could not keep my hand on them and the water that was pumping was cool. I am going to install new thermostats but I wanted to ask if the head gaskets were leaking would it ruin the new thermostats.Also if the water has good pressure does that indicate the water pump impeller is good or could this also be part of the problem. I appreciate your assistance.<br />Thank You<br />bay cruiser

 

[j_jtaylor]

Re: Yamaha 115 loss of power

I have the exact same problem with my 92 115 Yamaha, can you let me know how you solve the problem!

 

[rodbolt]

Re: Yamaha 115 loss of power

hello<br /> the filter I was refering to is a tiny inline filter on the pump intake side of the remote oil tank. its hidden and never gets changed, if the pump,t-stats and pressure relief valve are in good shape and the oil tank on the engine is staying between the lines then its time to remmove the heads and have a look. sounds like some nasties are building up in the passages. a classic sign of combustion gas leaking into a cyl is it runs well to about 4000 then overheats.you can test the sensors in a pot of water with an ohmeter and a candy thermometer.<br /> switch should close about 190 degrees. or 84-90*C.<br /> good luck and keep posting

 

[Anthony Mattera]

Re: Yamaha 115 loss of power

This is what I have done so far: Replaced the in-line one direction filter at the large oil tank,tested the thermostats they open at 134 degrees,tested the thermal switches they show an ohm reading at 193 degrees, replaced the water pump, flushed the engine with the stats removed while I had the foot off,disassembled and cleaned the oil tank on the engine,bled the oil pump for air, water tested the boat and when the alarm came on I took a temp reading of the heads and power head with a lazer pyrometer and the heads read 138 degrees and the powerhead was 80-90 degrees with the alarm on. I took a compression test and have 135 lbs. for each cylinder. This engine runs like a bear until the alarm comes on.I do not know what else to look for. What am I missing ?

 

[rodbolt]

Re: Yamaha 115 loss of power

hello<br /> wow<br /> you have a good one. while the alarm is sounding disconnect the pink wires at the heads. this will eliminate the sender switches<br /> if you have yammi gauges do you get any visuals. the next time it does this immediatly look at your oil tank. if the oil is not transferring fast enough you will get the exact symptoms you describe.or try to borrow the multi-function tach and see what the visual indicator is. it has to be one or the other.<br /> good luck and keep posting

 

[j_jtaylor]

Re: Yamaha 115 loss of power

Here is a reply from another forum as I have the same problem!! I dont know if it is of a lot of help but hey, it cant hurt!!!<br /><br />"I had the same problem with my 1990 115 Yamaha. It turned out to be the oil circuit in the tach/multimeter. It drove me crazy for a whole summer. I threw all kinds of money at it replacing everything in sight and none of it worked. I replaced the whole guage and it went away. I know that the guage is expensive but it works. I found mine online on the old bulletin board from a guy in New Hampshire".............<br /><br />Im sure you get the idea!!!! Hope its of some help!!

 

[Anthony Mattera]

Re: Yamaha 115 loss of power

Rodbolt & No rules<br />I really appreciate your help.<br />The alarm does go off when I disconnect the pink wire from the thermo switch. I would not chance running it with the wire disconnected not knowing what the problem is. My guages are barely visible and the yellow and green lights do not come on (I have tried this in the dark to see if the indicator lights are visible). Is there possibly a fuse that controls the indicator lights or there a way to disconnect the system. I noticed there are two cavities where the thermal switches can be placed in the heads.I am going to water test it again with another person running the <br />boat while I use the lazer pyrometer to capture a temp reading from the unused cavity to see what if temp reading varies as we reach the point where the alarm goes on. I am also going to try to perform a flow test from the pump to the manifolds. I am also going to check the setting on the rod adjustment for the oil pump, although it is going to full open when I throttle up.

 

[rodbolt]

Re: Yamaha 115 loss of power

hello<br /> leve the oil links alone<br /> they have absolutly nothing to do with the alarm system. all the system monitors is oil level and if the sensors are closed or not.<br /> buy another gauge. you can find them used. thats what they are there for.<br /> otherwise you can spend hours and beer money chasing ghosts.<br /> good luck and keep posting

 

[Anthony Mattera]

Re: Yamaha 115 loss of power

Rodbolt<br />I have found the problem, I water tested the boat with the thermal sensors disconnected,using a digital pyrometer I found that one cylinder head was getting up to 194 degrees in temperature and the other head had a high of 176 degrees.This was only at the area where the thermal sensor seats in the head, it never went any higher than 194.The thermostat area and all other parts of the head were reading 140-145 degrees. The power head was reading about 80 - 90 degrees.bay cruiser

 

[rodbolt]

Re: Yamaha 115 loss of power

hello<br /> now you must remove that head.<br /> use a hooked pik and carefully scrape any white scaley deposits. look for any sand build up. remove the head cover as well. carefully clean the blind passages by the t-stat pocket. for cleaning the heads I use a 3-m pad on a 1/4" shank. they are about 5 bucks a pop at wal-mart (AKA wallyworld) the pads work great dont strip aluminium just gaskets. they are black and about 3/8ths thick and look like coarse scotchbrite. DO NOT USE STEEL WIRE. once all traces of gaskets have been removed,and its tough. use acetone or other non-oily solvent to clean the mating surfaces. I use CRC-o6064 carb cleaner. then you can check the surface flatness with a straight edge and a feeler gauge. use mercury perfect seal or bombardier gasket sealer on the gaskets and try again. try to keep the debris out of the cyl ports. I use rags and tape. but you must make sure the block/sleeve area are clean. <br /> I usually reccomend doing both but its not nessasary.<br /> good luck and keep posting