1998 Mercury EFI 200 hp Overheat in rough water and rough idle.

[jebbers2016]

Serieal: 0G595336
Make/Model: 1998 Mercury EFI 200 2.5L
Max rpm: about 5800
Water psi: Idle is 5-7, WOT is 15+
Prop: 25 pitch Tempest 3 blade
Boat: 1998 BassCat Pantera Classic

I recently had the injectors serviced and the oil injection deleted on my 1998 Mercury EFI 200. When the mechanic re-installed my injectors, they replaced the seals. Twice now in roughish water I have got an overheat alarm running at mid speeds. Both times I shut the engine off immediately and got a tow or idled back after letting it cool down for a period of time. Before the alarm went off the first time, I noticed my motor was starting to idle pretty rough and it died on me at slow speeds multiple times. My engine ran fine at WOT in calm waters, and then a storm moved in and when I tried to run into the wind I got the alarm.

I took the impeller out and it was definitely in need of replacing, so I changed that out, including the gaskets and housing, and hooked a hose to the flush port on the back of the engine. When I did this I noticed that water only briefly sprayed out the tell-tale. I have a decent stream out of the tell-tale once the engine is warm in the water. After replacing the impeller I took the boat to a tournament, and it was calm weather. The boat did fine on plane with no alarms, however as the day went on it began to idle a bit more rough.

For the next day, I cleaned off my plugs and there was a good amount of oil around them, so I wonder if they may be fouled. The engine now seems to bog down when I give it gas to get on plane, but then it takes off after a few seconds and sounds fine. It idled fine early in the morning but got more rough the more I idled around the dock. It was windy when I went to take off across the lake and about 1 minute into my run against the wind, I got the overheat alarm.

My next thoughts are that I should replace the thermostats and the poppet valves, but I am worried that the injector service may have something to do with it.

I should also add when the oil injection was deleted they measured my tank and added oil to the gas already in the tank. When I added more gas, I put in a few extra ounces just to be on the safer side. Is it possible that the idle issue is because my plugs have been fouled? Last fall I had no idle issues or overheat issues and the boat had been put up since October. The jack plate has not been adjusted by me, and I have only had the boat since last July.

Any ideas or suggestions would be greatly appreciated as this issue seems a bit strange to me.

[leonreno]

First, not really recommended to run the motor with the water hose connected to the flush port, many times it will not provide sufficient water to either cool the motor or to keep the impeller from burning up. Run the motor on good muffs or use a large container to put the lower unit in.

Fouled plugs is a definite possibility, we’re those plugs new or older before all this happened? Also sounds like it could be flooding.

[jebbers2016]

Sorry leonreno I should have clarified that I did not start the engine when hooked to the flush port. I got the boat in July and have not replaced the plugs myself. I am planning to do so, but I would like to burn some of that rich fuel first if it won't cause any further problems.

[leonreno]

That’s probably a good idea on the plugs. Just to be clear, the alarm is beeeeeeeeeeeeeeeeeeeeep, not a beep, beep, beep?

[jebbers2016]

Maybe someone with an older BassCat can correct me if I'm wrong, but its a constant alarm of extremely fast tones, which I assume is their version of the constant beep. Kind of like an old school fire alarm. It is not an intermittant beep and there are no pauses.

[EuropeanAM]

Maybe someone with an older BassCat can correct me if I'm wrong, but its a constant alarm of extremely fast tones, which I assume is their version of the constant beep. Kind of like an old school fire alarm. It is not an intermittant beep and there are no pauses.

NO, that is NOT correct. And warning tones are ENGINE specific (has nothing to do with the brand of boat the engine is mounted to).

That warning is CRITICAL: DO NOT run the engine until resolved!

Common causes include:

-Water in fuel
-Oil Pump Rotation Sensor or Magnet Problem
-Bad Ground for Warning Module
-Loss of Spark (or intermittent spark) on one cylinder
-Oil Pump Drive Gear Failure
-Bad Warning Module