corvette1 Posted October 1, 2009 Report Share Posted October 1, 2009 i have a 97 evinrude 2 stroke with carbs problem i was running at 4500rpm and then it go's down to 3000rpm then back 4500 then down to 3000 it does this about every 50 feet now the temp light is coming on water spray is normal gas filter was clean also i was told it could be a heat sensor any advice would help thanks Link to comment Share on other sites More sharing options...
Guest skeeter99 Posted October 1, 2009 Report Share Posted October 1, 2009 i have a 97 evinrude 2 stroke with carbs problem i was running at 4500rpm and then it go's down to 3000rpm then back 4500 then down to 3000 it does this about every 50 feet now the temp light is coming on water spray is normal gas filter was clean also i was told it could be a heat sensor any advice would help thanks 1. pickup in tank plugged 2. water in gas (unlikely) 3. float in carb stuck (either to lean or rich) likely or a peice of debris moving around in the carb bowl getting sucked onto jet (intermittent) 4. temp sensor 5. bad coil 6. bad plug 7. blown head gasket(do compression test) 8. bad electrical connection battery or main wiring harness (I had this problem) I am sure going through the above list one of them will lead you to the problem Link to comment Share on other sites More sharing options...
Garry2Rs Posted October 1, 2009 Report Share Posted October 1, 2009 About 90% of the outboard troubles I have ever had were caused by air leaks. Cracks in fuel lines, that are almost too small, will open on turns or at certain RPM's and you will lose your vacume. This causes the motor to lose RPM's as the fuel is cut off, but regain them when the crack closes and fuel flow is restored etc. Check all the fuel lines. If you find nothing, remove the float bowls and clean the ends of the needle valve that is attached to the float. It could have crap on it that is causing it to stick. While you have the float bowl in your hand, check for cracks where the fuel line attaches to the bowl. I had a cracked float bowl on an Evenrude 120hp. that caused much the same problem as you discribe. Garry2R's Link to comment Share on other sites More sharing options...
JohnF Posted October 1, 2009 Report Share Posted October 1, 2009 Just a thought for one easy check. I haven't played with outboards for years, but if that was one of my old sleds I'd be pulling the plugs to check their colour. If they're really white on the tip I'd say you have some kind of fuel obstruction or float problem (if it has float carbs) that's leaning out the mix. That could cause the intermittent hesitation and the periodic overheating. If they're really white get it sorted out quick. JF Link to comment Share on other sites More sharing options...
Bernie Posted October 1, 2009 Report Share Posted October 1, 2009 Jeez...where are the guys yelling ....SEAFOAM ! It's going into "limp" mode. The module is sensing the overheat or maybe another problem and limiting the RPM. Time to hook up the scanner. Link to comment Share on other sites More sharing options...
Jack-of-all-fish Posted October 1, 2009 Report Share Posted October 1, 2009 Corvette1, I assume that by your mention of carbs that this is not a FICHT engine. As you know they're fuel injected. The heat sensor on carburated engines only turns the temperature warning light on and is likely a symptom rather than a cause of your problem. This said then I'd be looking at a cause of the engine running hot. I'd look at the following items: Thermostat -could be stuck closed or partially closed - Does the engine seem better or OK when you first start it up cold? -if so, replace the thermostat. Compression test - You could have a leaking headgasket. Lean fuel mixture- lean mixtures cause high running temperatures - as John mentioned look at the colour of the spark plug porcelain insulators - they should be a light tan colour if the mixture is correct, they will be very white if the mixture is too lean, lean mixtures are caused by carburation or fuel supply problems. There's plenty of other possibilities but these items are where I'd start. Link to comment Share on other sites More sharing options...
Bernie Posted October 1, 2009 Report Share Posted October 1, 2009 The heat sensor on carburated engines only turns the temperature warning light on and is likely a symptom rather than a cause of your problem. These engines had a system that OMC called "SLOW". It has a module that if it detects a problem it will reduce engine RPM in order to help prevent engine damage. Faulty temperature sensors are a common problem. It doesn't need to be fuel injected to be controllable. Link to comment Share on other sites More sharing options...
msp Posted October 1, 2009 Report Share Posted October 1, 2009 One thing I know about the Ram Ficht injection system is that the sparkplug alignment is very important. If they are out 1/8 of an inch it will not fire properly. My father runs that same engine and had the same problem when he had changed the plugs himself. Since he went to an authorized dealership they set him straight with new factory installed plugs. I know that this model has had its share of problems. Good luck Link to comment Share on other sites More sharing options...
JohnF Posted October 1, 2009 Report Share Posted October 1, 2009 One thing I know about the Ram Ficht injection system is that the sparkplug alignment is very important. If they are out 1/8 of an inch it will not fire properly. My father runs that same engine and had the same problem when he had changed the plugs himself. Since he went to an authorized dealership they set him straight with new factory installed plugs. I know that this model has had its share of problems. Good luck Sorry. I know I haven't kept current on things mechanical but what is spark plug alignment? The spark plugs as we used to use them simply screwed into a tapped hole till they were snug - end of story. JF Link to comment Share on other sites More sharing options...
Bernie Posted October 1, 2009 Report Share Posted October 1, 2009 Sorry. I know I haven't kept current on things mechanical but what is spark plug alignment? The spark plugs as we used to use them simply screwed into a tapped hole till they were snug - end of story. JF The way the combustion chamber and the fuel charge is shaped they don't want the electrode over the spark plug interfering. What happens is it will create a vacuum around the spark and it will misfire. Kind of a pain in the butt the first time you do it but it gets easy after a few times. I just grab a few boxes of them and go at it. My 'Rude needs a new set for next year but they have lasted 3 seasons and around 250 hours of running. Car racers have been indexing spark plugs for years. Hemi's were especially responsive to this. Link to comment Share on other sites More sharing options...
JohnF Posted October 1, 2009 Report Share Posted October 1, 2009 The way the combustion chamber and the fuel charge is shaped they don't want the electrode over the spark plug interfering.What happens is it will create a vacuum around the spark and it will misfire. Kind of a pain in the butt the first time you do it but it gets easy after a few times. I just grab a few boxes of them and go at it. My 'Rude needs a new set for next year but they have lasted 3 seasons and around 250 hours of running. Car racers have been indexing spark plugs for years. Hemi's were especially responsive to this. Gotcha. I vaguely remember some discussion along those lines back in the day. I thought the side-firing plugs took care of that. (I forget what they were actually called, the ones with no hook on 'em) JF Link to comment Share on other sites More sharing options...
ecmilley Posted October 1, 2009 Report Share Posted October 1, 2009 the 115 i would guess is a intruder/faststrike v4? while they are great engines they can have issues. is your water spray warm or hot? i had a similar problem this year running with a plugged intake lots of water at idle but no enough volume at plane and it activated the slow system. (now i have a water pressure guage) you could even have a stuck t-stat you do have two of them and when was the last time you reversed flush the enging? just throwing some of this out there Link to comment Share on other sites More sharing options...
Jack-of-all-fish Posted October 1, 2009 Report Share Posted October 1, 2009 These engines had a system that OMC called "SLOW". It has a module that if it detects a problem it will reduce engine RPM in order to help prevent engine damage. Faulty temperature sensors are a common problem.It doesn't need to be fuel injected to be controllable. Thanks for straightening me out on this Bernie. I was unaware of this safeguard type system. Link to comment Share on other sites More sharing options...
Bernie Posted October 1, 2009 Report Share Posted October 1, 2009 Thanks for straightening me out on this Bernie. I was unaware of this safeguard type system. No problem. I wasn't sure so I asked the outboard guys in our shop. ecmilley's suggestion about poor water flow could also easily be the issue too as well as other problems. John, I think they were called surface gap plugs. Not too common, they tended to foul easily. Link to comment Share on other sites More sharing options...
corvette1 Posted October 2, 2009 Author Report Share Posted October 2, 2009 thanks guys for all the reply's when i find the problem i will post thanks again Link to comment Share on other sites More sharing options...
Bernie Posted October 2, 2009 Report Share Posted October 2, 2009 I just reread your original post and wondered if 4500 RPM is full throttle? If so you may be overpropped, I think it should be 5000 to 5500. Link to comment Share on other sites More sharing options...
JohnF Posted October 2, 2009 Report Share Posted October 2, 2009 No problem. I wasn't sure so I asked the outboard guys in our shop.ecmilley's suggestion about poor water flow could also easily be the issue too as well as other problems. John, I think they were called surface gap plugs. Not too common, they tended to foul easily. They were the big deal for air cooled 2 strokes back in the early seventies. And yes, they tended to foul easily. We often ended up running different heat ranges on the hot and cool sides to try to balance the burn. Not sure we ever got it right though. JF Link to comment Share on other sites More sharing options...
ecmilley Posted October 2, 2009 Report Share Posted October 2, 2009 I just reread your original post and wondered if 4500 RPM is full throttle?If so you may be overpropped, I think it should be 5000 to 5500. i have the manual at home the v-4 and the v-6 produce max power at 4800rpm though i can run mine at 5100 Link to comment Share on other sites More sharing options...
corvette1 Posted October 3, 2009 Author Report Share Posted October 3, 2009 hi bernie full throttle is 5300rpm i was going 4500 when this started acting up Link to comment Share on other sites More sharing options...
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