GrindKore
Petty Officer 1st Class
- Joined
- Jun 20, 2008
- Messages
- 211
Hi guys my 2005 Mercruiser 5.0 TKS (carb 220HP) has recently developed a problem. When cold it starts up right away although at idle speed it tends to run rough with engine rpm varying between 800-600 rpm. When advancing throttle it hesitates but quickly recovers and is able to reach WOT @4800. At cruising speed I do notice slight hesitation when running 3600 RPM at is seem to drop 100 rpm or so and recover.
This issue has cropped up recently. The engine was easy to start at the beginning of this season and has never exhibited any issues. Today we were out fishing and when we decided to move to a different spot I had hard time getting the engine started. The only way it would start is when I advanced throttle in fast idle and wait for RPM to stabilize. It will not start when throttle is in idle once engine is warmed up. Once started though it will idle, however it does run rough and RPM fluctuates at low RPM range more.
I have checked all the basic stuff already while on the lake;
1) I do not belive venting is an issue, first thing I did today on the lake is unscrew the fuel cap to see if there is vacuum in the tank. There was none and it did not help with the starting.
2) I have replaced the fuel filter/water separator, this did not make any difference. Furthermore I drained the contents of the old fuel filter in to a clear plastic bottle and fuel was clear of any water or other contaminants.
3) Fuel is in good condition. We have refueled the boat last November with 89 octane non ethanol marine gas and I have treated it with marine sta-bil additive before storing the boat. So gas is about 6 to 8 month old and is treated with sta-bil.
I'm looking for suggestion as to how to approach diagnosing this problem. My next step is likely to get an ignition tune-up kit with new distributor cap, cables and spark plugs. I believe the engine still has the factory originals. However I don't want to throw parts at it blindly, and need some advice.
Thanks.
This issue has cropped up recently. The engine was easy to start at the beginning of this season and has never exhibited any issues. Today we were out fishing and when we decided to move to a different spot I had hard time getting the engine started. The only way it would start is when I advanced throttle in fast idle and wait for RPM to stabilize. It will not start when throttle is in idle once engine is warmed up. Once started though it will idle, however it does run rough and RPM fluctuates at low RPM range more.
I have checked all the basic stuff already while on the lake;
1) I do not belive venting is an issue, first thing I did today on the lake is unscrew the fuel cap to see if there is vacuum in the tank. There was none and it did not help with the starting.
2) I have replaced the fuel filter/water separator, this did not make any difference. Furthermore I drained the contents of the old fuel filter in to a clear plastic bottle and fuel was clear of any water or other contaminants.
3) Fuel is in good condition. We have refueled the boat last November with 89 octane non ethanol marine gas and I have treated it with marine sta-bil additive before storing the boat. So gas is about 6 to 8 month old and is treated with sta-bil.
I'm looking for suggestion as to how to approach diagnosing this problem. My next step is likely to get an ignition tune-up kit with new distributor cap, cables and spark plugs. I believe the engine still has the factory originals. However I don't want to throw parts at it blindly, and need some advice.
Thanks.