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Author Topic:   Help with power loss

decfishfoto posted 12-18-2003 08:07 PM ET (US)
i have a 90hp yamaha on a 17ft whaler. Recently developed a problem where the engine suddenly loses power as if it is not getting gas.Engine will rev all the way in neutral.this problem only occurs under power- in gear. I have changed the plugs, replaced the fuel filers-two separate lines, and cleaned out the filter under the cowling.Th e boat comes to the dock and next time out starts perfectly and functions well for an hour and then loses power again. Fuel tanks are full, filters replaced....what do you think is wrong and where should turn to next. Carb stuck?...vapor in line?? any thoughts would be appreciated
whalersman posted 12-18-2003 08:35 PM ET (US)
Sounds like it could a Power Pack or Ignition Coil(s)..
I had the same thing happen to me on a V6 Evinrude... It turned out to be one of the Power Packs...
Joe
decfishfoto posted 12-18-2003 08:52 PM ET (US)
Joe...thanx for the reply.Pardon my ignorance but was does the powerpak do and where do i find it?.....it's interesting that this seems to be aproblem of "build-up"; i.e.,it takes a while to develop.The engine has to run at crusing speed for 12-15mi or 40min and then develops the probledm and power loss. Is there a way to test the pak and the coil and would that be the way to go rather than the yamaha dealer.? thanx in advance. David
triblet posted 12-18-2003 09:03 PM ET (US)
1. Cleaned out the filter under the cowling? If there was
more than a couple of grains in it, you have a problem with
junk in the tank.

2. Check the connection at the tank. If it's leaking air,
you will get a loss of power at full throttle. Try pumping
the bulb while you have bad power. Try pushing the
connection onto the tank while you are having the problem.
Chuck
kglinz posted 12-18-2003 09:16 PM ET (US)
Is your fuel tank properly vented. An hour is a long time to run if the problem is a filter or an obstuction. Is the "primer bulb" hard or soft when it quits.
rubadub555 posted 12-18-2003 09:34 PM ET (US)
Is your tank creeping back to pinch fuel line?
Happened to me; strap fixed it.
tlynch posted 12-18-2003 09:42 PM ET (US)
I had the same problem that whalersman had with my Johnson 150. I also had the same solution - a new powerpack.
I bet the engine is cutting out on one cylinder. What I did is this:
When the engine acted up, I put it in neutral. One at a time, I removed the spark plug caps, and then put them back on to the plugs. Do this with one hand and keep your other hand away from the engine block. You will be able to feel/see/hear if the plug has good spark immediately. If you prefer - you can use an inductive timing light to test each plug wire for current. My way is more fun.
I bet your problem is electrical and your problem will either be a coil or a powerpack. A powerpack is sort of like a distributor. Someone here can tell you if you have 2 powerpacks on your engine or just one, if you do, you can swap them and see if the problem moves. If not, swap coils and see if the problem goes away. If not, I would think it is the powerpack.
Regardless, test each plug to see if the problem is mechanical or electrical.
Todd
whalersman posted 12-18-2003 09:45 PM ET (US)
The Power Pack supplies power to the individual coils and then from there to the Spark Plug(s). On my 70hp Evinrude, there was 1 Power Pack that was connected to 3 Coils and then their respective Spark Plugs. On my V6 Evinrude, there were 2 Power Packs that were connected to a bank of 3 Coils and Spark plugs.. I am not sure how the Yamaha is set up.. 1 or 2 Power Packs...
One way to check the spark of the above items without purchasing the high dollar test equipment was suggested by a fellow forum member and that is to use a Timing Light.
When this trouble happens, have an assistant hook up the Timing light and see if all the Spark Plugs wires are getting spark. If 1 or 2 Plugs are not getting spark, then you have to start narrowing it down to either a bad coil, more then one coil, or if the whole bank is out, then it would be the Power Pack.
Joe
whalersman posted 12-18-2003 10:24 PM ET (US)
Todd,
You beat me to the punch... Good Job....
Joe
Clark Roberts posted 12-19-2003 08:19 AM ET (US)
Sounds like a fuel delivery problem... above advice is good. Suggest you check compression pronto as lean fuel to air ratio will cause damage quickly. If you don't have a gauge or know how to do it find a buddy who does or get to a mechanic before you end up with a ruined engine! Happy Whalin'... Clark... Spruce Creek Navy
PS> you don't say but if symptom occurs at throttle up from cruise or only when trying to go full throttle then my money is on leaned out fuel. If boat suddenly drops off plane down to idle that's another clue.
Steve Leone posted 12-29-2003 08:29 PM ET (US)
I have a complete 1989 90hp Yamaha. Oil injected. $1250.00
bothedog posted 01-05-2004 08:19 PM ET (US)
70 hp Johnson ... same problem. Turned out to be the power pack also.

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Author	Topic: Help with power loss
decfishfoto	posted 12-18-2003 08:07 PM ET (US) i have a 90hp yamaha on a 17ft whaler. Recently developed a problem where the engine suddenly loses power as if it is not getting gas.Engine will rev all the way in neutral.this problem only occurs under power- in gear. I have changed the plugs, replaced the fuel filers-two separate lines, and cleaned out the filter under the cowling.Th e boat comes to the dock and next time out starts perfectly and functions well for an hour and then loses power again. Fuel tanks are full, filters replaced....what do you think is wrong and where should turn to next. Carb stuck?...vapor in line?? any thoughts would be appreciated
whalersman	posted 12-18-2003 08:35 PM ET (US) Sounds like it could a Power Pack or Ignition Coil(s).. I had the same thing happen to me on a V6 Evinrude... It turned out to be one of the Power Packs... Joe
decfishfoto	posted 12-18-2003 08:52 PM ET (US) Joe...thanx for the reply.Pardon my ignorance but was does the powerpak do and where do i find it?.....it's interesting that this seems to be aproblem of "build-up"; i.e.,it takes a while to develop.The engine has to run at crusing speed for 12-15mi or 40min and then develops the probledm and power loss. Is there a way to test the pak and the coil and would that be the way to go rather than the yamaha dealer.? thanx in advance. David
triblet	posted 12-18-2003 09:03 PM ET (US) 1. Cleaned out the filter under the cowling? If there was more than a couple of grains in it, you have a problem with junk in the tank. 2. Check the connection at the tank. If it's leaking air, you will get a loss of power at full throttle. Try pumping the bulb while you have bad power. Try pushing the connection onto the tank while you are having the problem. Chuck
kglinz	posted 12-18-2003 09:16 PM ET (US) Is your fuel tank properly vented. An hour is a long time to run if the problem is a filter or an obstuction. Is the "primer bulb" hard or soft when it quits.
rubadub555	posted 12-18-2003 09:34 PM ET (US) Is your tank creeping back to pinch fuel line? Happened to me; strap fixed it.
tlynch	posted 12-18-2003 09:42 PM ET (US) I had the same problem that whalersman had with my Johnson 150. I also had the same solution - a new powerpack. I bet the engine is cutting out on one cylinder. What I did is this: When the engine acted up, I put it in neutral. One at a time, I removed the spark plug caps, and then put them back on to the plugs. Do this with one hand and keep your other hand away from the engine block. You will be able to feel/see/hear if the plug has good spark immediately. If you prefer - you can use an inductive timing light to test each plug wire for current. My way is more fun. I bet your problem is electrical and your problem will either be a coil or a powerpack. A powerpack is sort of like a distributor. Someone here can tell you if you have 2 powerpacks on your engine or just one, if you do, you can swap them and see if the problem moves. If not, swap coils and see if the problem goes away. If not, I would think it is the powerpack. Regardless, test each plug to see if the problem is mechanical or electrical. Todd
whalersman	posted 12-18-2003 09:45 PM ET (US) The Power Pack supplies power to the individual coils and then from there to the Spark Plug(s). On my 70hp Evinrude, there was 1 Power Pack that was connected to 3 Coils and then their respective Spark Plugs. On my V6 Evinrude, there were 2 Power Packs that were connected to a bank of 3 Coils and Spark plugs.. I am not sure how the Yamaha is set up.. 1 or 2 Power Packs... One way to check the spark of the above items without purchasing the high dollar test equipment was suggested by a fellow forum member and that is to use a Timing Light. When this trouble happens, have an assistant hook up the Timing light and see if all the Spark Plugs wires are getting spark. If 1 or 2 Plugs are not getting spark, then you have to start narrowing it down to either a bad coil, more then one coil, or if the whole bank is out, then it would be the Power Pack. Joe
whalersman	posted 12-18-2003 10:24 PM ET (US) Todd, You beat me to the punch... Good Job.... Joe
Clark Roberts	posted 12-19-2003 08:19 AM ET (US) Sounds like a fuel delivery problem... above advice is good. Suggest you check compression pronto as lean fuel to air ratio will cause damage quickly. If you don't have a gauge or know how to do it find a buddy who does or get to a mechanic before you end up with a ruined engine! Happy Whalin'... Clark... Spruce Creek Navy PS> you don't say but if symptom occurs at throttle up from cruise or only when trying to go full throttle then my money is on leaned out fuel. If boat suddenly drops off plane down to idle that's another clue.
Steve Leone	posted 12-29-2003 08:29 PM ET (US) I have a complete 1989 90hp Yamaha. Oil injected. $1250.00
bothedog	posted 01-05-2004 08:19 PM ET (US) 70 hp Johnson ... same problem. Turned out to be the power pack also.