2001 Mercury 150 EFI Model Number 0T265622

[jcar968]

Need help with problem. Boat starts up and runs poorly for sometimes 30 to 40 minutes, then it kicks in and runs fine rest of day. I have replace spark plugs, drained fuel tank and replaced all fuel lines from tank to motor, and replaced water separator.I have also tested spark from all coils and they seem to be firing, when I watch my Tach nothing changes when I pull the bottom two plug wires. So for some reason bottom two cylinders are dead, Could this be electrical problem or a fuel injector problem?

 

[Fun Times]

Hi there, welcome to iboats!

If there seems to be a problem with the bottom two cylinders and nothing seems to be happening when you remove the two plug wires then you'll want to first test to see if they are firing while cold. One easy trick to see if each plug wire is getting spark is to connect a timing light to each spark plug wire while the engine is running and see if the light is flashing at very consistent rate.....If not then you either have bad wiring someplace or a bad CDM MODULE ASSEMBLY (#827509T 7) available here at iboats http://www.iboats.com/Boat-Parts-Acc...137?q=827509T7

Here's a parts catalog for your engine model,
https://www.perfprotech.com/mercury-...g/umodel/18096

 

[CharlieB]

Just for giggles, ALWAYS test compression.

I've had a couple of EFI's have a noticeable compression drop when cold. Once warmed it was restored and so was performance.

A decarb melted or washed out the gum that was holding the piston rings from moving freely cold.

Most likely a defective module or trigger. But all troubleshooting properly starts with compression and spark test. Every time, just so you can be sure if it is mechanical or electrical.

 

[Faztbullet]

My bet is inner switch box bad......the ECU picks up signal off switchbox(#3 if I remember) to fire #5 & #6 injectors. Its not the trigger as pairing is off and doubt its CDM as usually if it fails it stays failed..

 

[jcar968]

Thanks for the responses. I ran the boat this weekend and Saturday same issue, ran bad for about three miles then kicked in and ran fine rest of the day. Sunday morning it ran fine for about thirty minutes and I killed it for a minute then restated it and it ran poorly again for most of the morning then later it kicked in and ran fine rest of the day. I have not done a compression test yet, but i am sure that the coils are firing. Fastbullet what inner switch box are you talking about?

 

[jcar968]

On the CDM Module Assemblies I have swapped them and spark plugs with other cylinders and there was no change.

 

[Faztbullet]

Sorry just noticed year and no switchbox ....

 

[jcar968]

Thanks. CharlieB what is the trigger you are talking about.

 

[CharlieB]

Item 12 at http://www.mercruiserparts.com/bam/subassembly/28560/11209/50

Do NOT buy this part yet. It is also possible for one CDI Module to be faulty and that can force the second module to hold it's spark. If this is so replacing the one defective module will restore spark on both modules. However, you cannot 'assume' that it is a module yet.

Download and study the DCI Ignition Troubleshooting Guide

CDI Troubleshooting-Guide-Inside-Pages.pdf

This guide includes troubleshooting steps for your ignition. Diagnose and PROVE the guilty part before ordering anything. You will need a decent Volt/Ohm Meter and a DVA Adaptor. You can build an adaptor cheap and easily, directions are posted here. A remote starter button can be very handy, otherwise you may need a helper to turn the key to crank the motor.

Simple, easy to make DVA adapter for standard Multimeter

Only after proving the faulty part is it safe to spend money on any NON-returnable electrical part.

 

[jcar968]

Thanks. I will check this out. Do you know what controls the injectors?

 

[CharlieB]

EFI uses an ECU. An electrical processor mounted in a box with a bunch of wires going to everything. ECU's don't magically work again after they fail. And they are not cheap. It is possible for a driver on the circuit board to fail and one injectors fail to spray. There is a company that can repair the circuit board. But you are nowhere near that deep into this yet.

KISS Principle. Begin testing following the step by step instructions in the service manual. Only then will you begin to sort out the problem.

As always, since there is NO RETURN on electrical parts, it is highly recommended that testing to PROVE a part defective before spending any money.