Engine Issues 1999 Mercury 225EFI

[aproffitt]

Hi guys,

This is my first post. While researching some engine issues I found this forum and thought this may be a good place to post about my problems.

I have a 1999 Proline 2950 with twin 1999 Mercury 225 EFI engines. I bought the boat last September, and the engine issues weren’t apparent during the survey and sea trial.

The trip home with boat was from Queens, NY to Point Pleasant, NJ. Seas were 4-6 feet from the Verrazzano Narrows to her new berth in NJ. This is where the problem first presented itself, and the issue continues intermittently in somewhat rough weather. What happens is the RPM on the port side, and occasionally on the starboard side, will drop from 4200 to 2500 when the boat pounds hard or when the bow gets buried in a wave. An additional problem, and may be related, is that the boat hates to run between 2500 and 4200 rpm. It typically bogs down and then the rpms jump right up to 4000+ rpms when getting on plane.

This spring I did a basic tune up. This consisted of changing the water separators, fuel filters, plugs and wires. I checked the spark the old fashioned way (arc to block), and all seemed to be ok. I checked the compression, it was so-so. All cylinders on the starboard side were between 105psi and 115psi. On the port side all cylinders were between 95psi and 105psi. I’m know this isn’t great, but at least it was even. I don’t think this is fuel related, the boat has two tanks and I switched them so starboard ran on port and have had the same results.

Just recently in calm protected water the boat engines turned 5000 rpm fully loaded (fully loaded for me is adults, 2 kids, 300 gallons of gas, 40 gallons of water, and a decent amount of fishing tackle) and made 34 knots. This was with a dirty bottom and without trimming the bow up, both would’ve provide higher RPMs and top speed.

Anyone have any similar experiences with their 225 EFIs, or have any recommended tests to start with? Your input is appreciated.

Thanks,
Al

[JOE54]

see if the float is too high or saturated on that mtr sloshing fuel out of overflow in rough water

[EuropeanAM]

If you would, please take a moment to review the Announcements at the top of the Forum, and be sure to provide the Required Info (serial number) when posting. Thanks!

Might also want to check battery connections and the cannon-plug connectors (disconnect, clean male pins, spread male pins slightly, reconnect and strap in place properly).

[aproffitt]

Hi,

The serial numbers are 0G8050421 and 0G680276.

Thanks,
Al

[EuropeanAM]

Thanks, Al. That first number has too many digits.

Definitely check the cannon plugs as recommended in Post# 3.