1997 Mariner 175 efi hard to start cold

[jtipton91]

Got a 1997 mariner 175 efi. Sn# 0g549797
Just got thst boat, very difficult to start motor. Will crank and try to start, occasionally starting but slowly dying right after.
Once i do manage to start and keep it running, it runs very rough until it warms up then it runs great.

Checked throttle position sensor it was reading 0 so i set it to .263v per the manual (port temp sensor disconnected while setting). Didnt seem to help.
I then tried unplugging the port head temp sensor and that seemed to solve the issue. Started and idles just fine.

Any ideas what the problem is?

[JOE54]

test or have tested cyl head temp sensor and air temp semsors , when you unplugged that sensor you changed the pulse rate of injectors /richens mixture

[jtipton91]

Ok will do. If they werent bad where would u go from there?

[JOE54]

make sure it has and maintains correct fuel psi

[jtipton91]

Could the ecu be a possible issue?

[JOE54]

sure it could if pump quits running and has no fuel psi thats why i asked about correct fuel psi #3

[jtipton91]

Well its none of the above, tested all 3 by the book no help. Unplugged head temp sensor again and it fired right up.
Checked .462, idle timing 3 atdc max timing 20btdc.
At a loss.

[JOE54]

you know anyone that has 200 close to same year model for ECU trial , injectors ever been cleaned ???? also there is a kit to install for choke operation from key switch to richen mixture up when cold , you posibly have a problem in your ECU cold enrichment curcuit

[jtipton91]

Ya i tried the mod to push key enrich. Didnt seem to work. I do have a 150 ecu on my other boat

[JOE54]

try it for a test see if it starts cold easier

[jtipton91]

Will do. Have a working 175 ecu on the way should be here tuesday

[jtipton91]

For people having this problem in the future, it was the ecu. Got a good one and put it on, no longer having any cold start problems.

[JOE54]