Fished all day last Wednesday - motor ran fine. Launched Thursday morning - motor started right up, ran fine for 5 minutes to a no-wake zone, idled smoothly thru zone - then jumped back up on plane at about 5200 rpm for a few minutes. Motor instantly dropped to about 4600-4700 rpm. Still running smoothly - still idleing smoothly. Still starting smoothly - turn the key - it starts - no vibration or missing. Been in the water three times since then - no change.
Here is what has been done/checked.
Motor has 450 hours.
Fuel water seperator dumped and was clear.
Injectors were pulled and cleaned - reinstalled.
New plugs installed.
Compression checked - all around 220 psi.
Injector leads sequentially disconnected while running to make miss - miss eliminated when reconnected.
Plug wires sequentially disconnected while running to make miss - reconnected and miss eliminated.
Suction filter on High Pressure fuel pump cleaned.
Motor usually runs about 5600-5800 rpm wide open and trimmed out - anybody got an idea what would cause a drop of 1000 rpm - with no other signs or indications of trouble.
I had the same motor but mine had an intermittent skip and it would lose rpm’s every now and then. I had an air leak at the antisiphoning valve and fixed that. It still had a little bit of a skip though. I changed the HP filter and it ran great after that. I would definitely change out the HP filter if it has never been done, you are overdue. I have a manual for it in PDF if you are interested.
No lights on tach - that was the first thing I looked at - but thanks for the reminder - should have put that in the initial post.
Also - oil level is full - recent oil and filter change - vent on fuel fill is open and clear. High pressure fuel pump is audible and promptly charges fuel rail. After sitting overnite - requires no pumping of primer - just turn key and start.
Just a couple of checks. The pick up tube in the fuel tank may be clogged. Take it out and remove the screen. Change the primer ball. Check the fuel hose under the cowling for a rubbery stretchy feeling. Ethonol and additive can break down this hose so it collapses when under demand. Who cleans injectors locally? Normall they are sent off to a company like flagstone? Does it run the same on a six gallon tank? Also the fuel filer on the fuel pump needs to be changed not cleaned
Thanks Charles - have located a portable tank that a neighbor has on a 25 Yammy four stroke - I will make sure the vent is open and the cap is loose. Any idea whether the fuel connections on the two engines are compatible/same - or will I have to do some modification??
Thanks localdude - appreciate the input - I am eliminating the possibilities in the order that I can do myself - then will seek additional help if required.
I remember how frustrated I was trying to fix that skip. If you find it might be the filter, it takes 15 minutes to change it and I think it was $55 from ChrisV. My 05 140 was the best motor I have ever had. If I ever have a choice of motors again, they will be suzukis.
I remember how frustrated I was trying to fix that skip. If you find it might be the filter, it takes 15 minutes to change it and I think it was $55 from ChrisV. My 05 140 was the best motor I have ever had. If I ever have a choice of motors again, they will be suzukis.
Just ran the boat on the aforementioned six gallon tank - no change - still 4800 rpm max. Next??
186 Bone Flats Boat
140 Suzuki fourstroke
Did you connect straight to the motor?
Check the hoses to see if they flatten while under pressure?
New racor
new fuel filter
new high pressure pump filter
clean injectors
there is. Fuel restriction somewhere
did you ck compression
filter
Connected straight to motor - vent open and cap on loosely. Compression on all cylinders was 220 - 225 psi. Will concentrate now on hoses and filters and pumps on the motor since boat hoses/filters are eliminated. Correct??
Yes, the injectors were subjected to voltage - in both polarities - cycled as fast as we could manually while under pressure with cleaner, also placed in ultra-sonic cleaner and solution. Admittedly probably not as good as a “flagstone” or whoever - but thats what we did.
if you pumped the primer bulb while it was running, and it was firm, and it made no difference in rpms, its not likely the boat.
I am leaning toward high pressure filter