2005 Mecury 90 4-Stroke trim gauge and rough idle issues

[ChevyReb]

OK, I recently picked up an 05 22' Lowe Sun Cruiser Trinidad 220 with an 05 Mercury four stroke 90 HP engine. The boat has been sitting virtually unused for a few years. I have run a couple of tanks of fuel cleaner and sea foam to try and clean it out a bit. It usually starts right up but has a little stumble at idle and at very low speed. I have had a couple of times where I had to turn it over a few times to get it running...it's like it's not getting gas but the bulb is tight. After you throttle up a little it smooths out and seems to run great. I have not replaced the plugs yet and am planning that next to see if it makes an improvement. If there are any other things I should look at please let me know so I can try them.

Second issue is that the tilt/trim gauge on the console reads full up no matter what position the engine is at. So I would like to know how to determine if the issue is with the gauge or the sending unit at the engine? Also sometimes the tach gets a little jumpy and seems to read higher when the sound of the engine remains constant. Can anyone give me some direction here to help troubleshoot these please?

That's all for now.

Thanks!!!

[ChevyReb]

Bump ttt

[raymor]

Sounds like a fuel issue. Did you check the fuel pressure on the fuel rail? Could be the VST tank needs a good cleaning as the screen on the electric fuel pump might be clogged. I believe you have a mechanical pump that pumps up to the VST tank so I guess you have to track down where your not getting fuel.

[PontoonboatFun]

if it is an EFI 4 stroke> may be the cracked tube problem in the fuel module at the front of the engine. having problem on 115mercury EFI 4 stroke and was looking for any others having the problem. found it to be very common. I have fixed mine. advise if that is it.

2) side on motor is the trim indicator. in an up down pin. Follow the wires on the outside on the transom. Easy to clean out of water. work on wiper system copper>Mine needed cleaning this year on a mercurser.

[ChevyReb]

Sounds like a fuel issue. Did you check the fuel pressure on the fuel rail? Could be the VST tank needs a good cleaning as the screen on the electric fuel pump might be clogged. I believe you have a mechanical pump that pumps up to the VST tank so I guess you have to track down where your not getting fuel.

No I have not tested fuel rail pressure. I need to get a service manual so I can see what these terms are like "VST tank"

[ChevyReb]

if it is an EFI 4 stroke> may be the cracked tube problem in the fuel module at the front of the engine. having problem on 115mercury EFI 4 stroke and was looking for any others having the problem. found it to be very common. I have fixed mine. advise if that is it.

I think it is EFI but the boat is at the upholstery shop since Friday a week ago. I should get it back this Friday and will l can check this then...where is the tube located and is it easy to visually tell if it's cracked?


2) side on motor is the trim indicator. in an up down pin. Follow the wires on the outside on the transom. Easy to clean out of water. work on wiper system copper>Mine needed cleaning this year on a mercurser.

Sorry but I am not sure what you mean in 2) above. what is "side on motor?) and system copper? Do you mean clean the copper wire ends? Can you post a picture of what you are describing?

Thanks for the input!

[PontoonboatFun]

suggest best to get the serial number and look parts pictures on iboats.com to see diagram of your arrangement. not talking about electrical issues. look at fuel system and tract your system to look up points. I have a 115 4stroke EFI. you may not have the exact model type of fuel system. Mine has a fuel vapor canister/ fuel module and the pump are in it. That were we found my problems. good luck. replace factor hose with copper tubing.