F225 rough idle and low rpm

[ItalianAngler]

2002 motors. 2200 hours.

Ran the boat for a solid hour a couple weeks ago. Came down off plane to for a min and noticed stbd engine vibrating. Powere back up and fished all day but it seemed to vibrate intermittently until around 2200 RPM then ran fine

Ran home 2 hours, coming down off plane and idling through the creek it was rough, vibrated, and sounded like crap.

Yesterday fired it up and ran in the slip for a few, stalled. Fired it back up and it’s purring. Idled around the creek and cove beautifully. Went to put her under load and I couldn’t go past 1200 rpm, control seemed stuck. Stopped. Went into reverse and vrooom vrooom. Could do whatever u wanted and smooth as can be. Went back into fwd and ran no problem now up to normal cruise speed.
Came back home and sounded like crap vibrating again in the creek but if I throttle up down it’ll stop sometimes and run normally.

Any insight here? I’m guessing there is a sensor or switch of some kind going bad. I’ve seen mention of the shift position switch being an issue. When I throw it into R it’ll reset for some reason.

Checked my linkages and all seems as it should be. No corrosion any where visible.

 

[seasick]

It is possible that there is a neutral position switch but it would be an on-off type and generally if misadjusted you would have a dead spot when throttling. Taking a stab in the dark, I would look for a fuel issue. You may have a bad low pressure fuel pump. I don't know if that motor uses multiple LP pumps or a lift pump. I would guess multiple LPs. It's just a guess though. What model motors?

 

[ItalianAngler]

F225 TXRA

 

[seasick]

I had assumed the motors were 2 strokes. My bad.. I don't have a lot of experience with the 4 strokes and my advice probably doesn't apply to your issue.

 

[ItalianAngler]

Update, it also appears to be running rich.

 

[ItalianAngler]

Update: I replaced the plugs, it ran perfect until it was hot coming down off plane. Chugging again. Albeit not as bad as with the old plugs. Smoke at low rpm and idle but at WOT it still rips.

 

[seasick]

Update: I replaced the plugs, it ran perfect until it was hot coming down off plane. Chugging again. Albeit not as bad as with the old plugs. Smoke at low rpm and idle but at WOT it still rips.

That sounds like a rich mixture. At speed, you use more gas but as the speed lowers, the mixture is too rich and the plugs start to foul. The smoke should be dark and not blue. When you looked at the old plugs were they all the same or was one or more a lot more fouled?
If the later, you may have a sticky or stuck injector. There are other causes for a too rich mixture such as a temp sensor, manifold temp or air flow sensor ( not sure if you have one).

 

[seasick]

It occurred to me that you might have a bad coil. You can test somewhat by running the motor in neutral at about 1000 revs and pull off the spark plug wires one at a time. If that coil is good, the motor speed and sound should change when the wire if pulled. If not, you may have bad or no spark. Use a insulated pliers to pull the wires off. It is easy and panful to get shocked.

 

[ItalianAngler]

The bad coil is a theory I’ve had as well. Haven’t had the time to test it yet, this being said the bottom two plugs were gunkier than the rest. I assume oil sits in this area more so than other locations? My Yam mech (going purely by my description) said it sounded like I might have one throttle stuck open more than the others and we should sync. He’s gonna stop by next week, if I can’t get it straight beforehand.

 

[seasick]

The bad coil is a theory I’ve had as well. Haven’t had the time to test it yet, this being said the bottom two plugs were gunkier than the rest. I assume oil sits in this area more so than other locations? My Yam mech (going purely by my description) said it sounded like I might have one throttle stuck open more than the others and we should sync. He’s gonna stop by next week, if I can’t get it straight beforehand.

If yours is a multi carbed motor ( six carbs) do not touch the carb adjustments unless you have a multi-port manometers to sync the carbs. It is just about impossible to sync multi carbs without one. Believe me, I have been there