Does the throttle body get gummed up when not used on an mpi engine?

[The motor guy]

Haven't used the boat much the last 3 months or so. It was stumbling a bit past 3000rpm. I just kept it below 2500 or so for the first 30 minutes and it cleared up. I got to thinking and was like you know its got to be the throttle body getting hung up, not allowing the correct air to fuel mixture. This thing is fly by wire, so I dont know how you clean it. Just spray some throttle body cleaner on it? Do you do this running or not running?

 

[The motor guy]

The boat engine is a gm350 mpi so it's got injectors in the intake manifold.

 

[burbguy82]

This thing is fly by wire, so I dont know how you clean it. Just spray some throttle body cleaner on it? Do you do this running or not running?

remove air cleaner
spray some carb cleaner on the butterfly and round the ID of the TB
spray some carb cleaner on a rag
open TB by hand, and wipe with said rag
reassemble.

.....not running

 

[Mechanician]

Key on, engine off, you can usually just open the throttle control and have that keep it open for your cleaning.
A/F mixture is usually either MAF, or MAP sensor controlled, and fine tuned by the A/F sensor (if it even has one.)

 

[samven]

If it has an Electronic throttle body, dont spray anything in it. Your really should remove it (easy job) and put Throttle body cleaner on a rag and wipe it down being careful to keep liquid from getting into the electronic position sensor. You need to clean the ring around the area the plate sits and the edge of the butterfly. The edge that folds down is very difficult to clean from the top hence the need to remove it. All this said if you are not having problems idling cleaning this wont help much. TB problems usually manifest with low or rough idle, stalling when coming down from higher RPM. Once its open a little dirt does not affect it much.

 

[The_Jeff]

TB problems usually manifest with low or rough idle, stalling when coming down from higher RPM. Once its open a little dirt does not affect it much.

Yeah stumbling at decent load is something else-- I would guess ignition or fuel pressure.

 

[The motor guy]

Yeah stumbling at decent load is something else-- I would guess ignition or fuel pressure.

It only did it and couple times, then it was better. I dont get it. How so these people up north let their boats sit for like 7 months over the winter and I have issues anytime mine sits for more than a month

 

[samven]

Check your water separator and your filter. I have seen issues with water getting through that seems to clear up when the gas gets shaken up and you start pulling more through the separator. They seem to separate better with flow and leak when setting.

 

[The motor guy]

Check your water separator and your filter. I have seen issues with water getting through that seems to clear up when the gas gets shaken up and you start pulling more through the separator. They seem to separate better with flow and leak when setting.

It always does it on the first couple attempts at getting up on plane. So for example I start the engine and launch the boat, let it idle and warm up while I park the trailer. Then untie from the dock and idle through the no wake zone another 10 minutes or so and when I get out of the no wake zone is when it does the whole bogging down thing. Then it's okay. I usually just pull back the throttle. It's got a 10 micron racor and the fuel probably gets a little old at times. The gas in it now might be 4 months old. I filled it up with 30 gallons today before launching. It holds 118 gallons though. I just replaced a bunch of stuff on it last summer. New plugs, new exhaust manifolds, fuel filter etc. Can old gas stop up a 10 micron fuel filter? I have maybe 60hrs of run time in the last year or so. It ran like a top after I tuned it up last year and didn't do this bogging thing again until today. Oh I changed ged out the fuel pressure regulator too at that time. Hard to tell what fixed the issue last year as I did so much at once

 

[JDenyer232]

Old gas can definitely cause problems. Add marine stabil to the gas every time you fill up. I've been doing that for years for my outdoor power equipment and since i started doing that everything fires up the first time.

 

[The motor guy]

Check your water separator and your filter. I have seen issues with water getting through that seems to clear up when the gas gets shaken up and you start pulling more through the separator. They seem to separate better with flow and leak when setting.

Do boats pickup a lot of water in the fuel?

 

[samven]

Yes, is your gas cap on the gunnel, check to make sure the oring is in good shape, rain and spray will get in around that even if it has a cover over it. If it is vented and it should be, water gets in through the vent. In the summer a boat sits in as close to 100% humidity as you can get. If you have a choice dont use E10 gas, most marinas sell Rec90 at and outrageous price but its better than E10. If you can get to the fuel gauge sender (usually under a screwed down cover on the deck above the tank) you can get a water putty that you put on a long dipstick then put it in the gauge hole to the bottom and if there is water in the tank it will turn pink. While your in there make sure the gasket around the gauge plate is in good shape. No one checks them but any water that gets onto the top of the tank can enter there. and if your bildge pump ever runs then water is probably getting to the top of the tank.