1993 Mercury efi engine dies out under load

[Baseballnut]

93 Skeeter 175 with Merc 175 efi. Disclaimer: not an engine guy and new to forum.. just trying to trouble shoot. But I can follow directions... 2 week + wait at Merc shop. Motor Starts and runs great on trailer with muffs. Revs well, shifts fine. Drop it in water and whole nother story... starts fine, idles good, pumps water thru pee hole good. Boat in water dies after shifting forward or reverse. At friends garage... Things that has been done: replaced water pump.( was probably over due , boat sat for a year) drained the old crappy oil mixed gas, put straight marine gas in. Smoking exhaust back to normal. Seafoamed hot engine. Gas was mixed prior for fear of oiler not working.

What/ where do I start? Have been reading a lot on forums and see a lot of different things. 50 min from nearest ramp to test.

 

[Dukedog]

sat for a year with gas/oil in it?.. tha list is long..... but no sense in doin' one thing at a time then test.. '93?.. electric pump separate from vst with tha U shapd fuel line between 'em, right?

 

[Baseballnut]

Yes, had gas mixed, stored at bro’s house, didn’t use it much, then not at all for a while. It’s an XRi 2.5 L. Attached is photo. This is idling in tank. Boat is 93’ assume motor is factory. Will double check when back in town Monday. I think you are correct on pump being separate. Had fuel lines replaced and primer bulb when drained old gas.

 

[Dukedog]

several things will need ta be checked/cleaned/replaced.. probably a fuel delivery problem.. anything remotely ta do with gas delivery falls in this category.. if ya want send me an email addy and i'll send ya site for your oem manual.. will have some good information on problems and "how to" stuff..

 

[mav6759]

Sound like fuel injectors, I would seaform the motor and clean those injectors. I had the same problem with my carb's until I cleaned them. But it does sound like a fuel delivery issue.

 

[Baseballnut]

I will try that when I get back and update. Another mechanic mentioned back pressure while in the water???

 

[Dukedog]

not gonna be "back pressure"...

 

[Baseballnut]

Okay, good to know.

 

[Baseballnut]

Just an update. Didn’t have a chance to pull injectors yet. Had some other things I had to do. Had a mechanic check it out on loading ramp. Says it is flooding itself when put in gear. Had to pull out of water and clean plugs. Then started up again and did same at ramp.

i am out of town for a few days with sons baseball, will try to get injectors out Friday. Anything to replace when I get them out and cleaned ? O rings, gaskets? Said it was running rich. Is there a way to adjust running too rich?

 

[Baseballnut]

Considering to unbolt it and just drop in bottom of lake.

 

[havoc_squad]

Fuel injectors are the gateways of how much gas is put into the engine for each intake cycle of the engine.

So, the engine is getting flooded with too much gas for the given amount of air allowed in by the intake butterflies. Which I'm guessing is only idle air flow.

So, the following possibilities exist:

1. You have one or more fuel injectors stuck open, dumping gas into the engine. There is a straightforward test you can do to test them.

The following link is not for your particular outboard, however it does give a good guide on how to perform cleaning and testing fuel injectors on an outboard motor: https://youtu.be/jNaTmjpT20U?t=1180

2. If it is not the injectors, then you need to get the OEM service manual to see what possible other variables could be telling the injectors to open for way too much. It could be a sensor, a bad ground, etc., etc.

I would still recommend having the OEM service manual to get all the data needed to perform the needed checks on the motor.

This is no different than what a lot of automotive diagnostic technicians have to do on modern cars. A professional does not throw parts after engine codes, they read the manual and they diagnose the problem. That often times means DIY'rs have to pony up money for the needed diagnostic tools or take it to someone who does have those tools for specific problems.

 

[Baseballnut]

Thanks for the info. I have a owners manual link becoming available. I will check into this and hopefully get some answers this weekend on the injectors. I appreciate your time.