Problem getting to WOT

[pataterchip]

2001 Mercury 60HP bigfoot 4 stroke 4 cylinder.
I just rebuilt the carbs and had them synced at mercury dealer. Prior to that I went through and replaced fuel pump diaphragms and replaced gas lines. When I got it back from the dealer it was given a clean bill of health. This weekend I was running a new prop as my WOT Rpm's were very low with old prop. Every time I would got to full throttle the motor would climb to about 4000 Rpm and hold there for a mile maybe mile and half, then climb to 5500-WOT. While @ 4K i was playing with trim angle trying to find best angle. Every time it would take several minutes maybe 5-8 running at 4K before it would open up and get to WOT, at first I thought it was the trim angle but now I'm wondering if needs to get good and hot or I still have carb issues, or maybe just not the right prop. Your thoughts please.
Prior to decarbing all the usual compression test and spark test were done with no issues.

 

[tashasdaddy]

Re: Problem getting to WOT

it sounds like a carb or coil in not kicking in as it should. if the you have a carb, that is clogged, you have no lubrication going to those cylinders, which can be catastrophic.

 

[pataterchip]

Re: Problem getting to WOT

This motor is a 4 stroke.

 

[CharlieB]

Re: Problem getting to WOT

First thing is to check the set up of the boat/ motor combination. Check the mounting height of the motor, cav plate even to no more than one inch higher than the bottom of the keel and centered with the beam.

Check the bottom rear of the boat for any 'hook' that 'traps' water and kills speed underway.

Next, take along a partner pilot and a timing light, mark the flywheel timing mark and mark again at 180 degrees from the timing mark. Two cylinder should fire at each mark. Look at WOT timing to ensure that it is correct at 4000 and check again at 5500. Chances are the ignition module is not advancing timing fully and the engine hangs at 4000 until timing fully advances.

Verify the problem then contact your dealer for a replacement module or check with aftermarket sources such as CDI Ignitions.