1989 Mercury 100HP Bogging Issues

[shoots7066]

Hi Everyone,
Ive got a 100HP Mercury outboard 4cylinder. It is the model that has the trolling feature built in. At low idle, only (2) of the cylinders get gas. When the engine goes above 1800RPM, than the remaining two cylinders kick in. The issue with the enigne occurs when i try to accelerate quickly (pulling a skier). When i punch the throttle, the engine bogs down and hesitates for a few moments, than takes off. It runs great at high speeds and is fine if i take off slowly. All four cylinders have good compression. Someone mentioned its probably the lower rings but that doesnt sound right. It does idle a little rough and has trouble staying running at low idle. Any ideas on what could be casuing this? Thanks in advance for your help

 

[sschefer]

Re: 1989 Mercury 100HP Bogging Issues

Hi Everyone,
Ive got a 100HP Mercury outboard 4cylinder. It is the model that has the trolling feature built in. At low idle, only (2) of the cylinders get gas. When the engine goes above 1800RPM, than the remaining two cylinders kick in. The issue with the enigne occurs when i try to accelerate quickly (pulling a skier). When i punch the throttle, the engine bogs down and hesitates for a few moments, than takes off. It runs great at high speeds and is fine if i take off slowly. All four cylinders have good compression. Someone mentioned its probably the lower rings but that doesnt sound right. It does idle a little rough and has trouble staying running at low idle. Any ideas on what could be casuing this? Thanks in advance for your help

I highly recommend getting the Merc Service manual before you begin working on your engine.

Three likely causes:

1. Remove the oil tank and replace the 1/8" inline fuel filter for the mechanical injectors on #3 and #4 cylinders.

Test run..

2. Check the accellerator pump and make sure there is only .030 clearance at WOT. If it is set correctly replace it.

Test run..

3. Remove the stbd side electrical plate, remove and replace the two mechanical injectors on #3 and #4 cylinders.

Test run.

Optionally, do all three then test run.

Of course you can always do what I did and upgrade to a small V-6.