Winterizing Mercury 90-HP FOURSTROKE

[howlingdogsteve]

Hi All. I experienced an abnormal situation when winterizing our 2006 Mercury 90-HP FOURSTROKE. I hooked up the [hose adaptor for water cooling], turned on the water supply and started the [2006 Mercury 90-HP FOURSTROKE]. [The engine ran at] Idled for about 40-seconds. I did not see the water pressure increase from 0-PSI or witness any significant water flow from the confidence stream. I revved-up the [engine speed] to about 1,000-RPM and still [there was] very little pressure or flow.

The [water pressure in the cooling system of the engine would be] normally at 7 to 10-PSI. I [increased] the [speed of the engine] to about 1,500-RPM and the pressure went up to 3 to 4-PSI.

The confidence stream would repeatedly come out strong for a second or two, and then just a dribble, followed by strong, then dribble. When I reduced the throttle, [the water flow maintained this action]. It appeared to be cycling--as a saltwater inboard engine does.

I removed the lower unit to examine the impeller (expecting to see a damaged vane or two) but all was fine.

Could there be a blockage somewhere?

I am at a loss with this problem. Any diagnostic help or advice would be much appreciated. Thanks--Steve

[Phil T]

In the future, do NOT rev the engine past [1,000-RPM] when on the [hose adaptor]. There is not sufficient water pressure for cooling.

Check the outlet fitting (where the tell tale water exits the motor) with some trimmer line. Salt builds up and clogs the opening.

If the impeller is more that two-years-old, replace as a precaution.

[howlingdogsteve]

Thanks Phil. I checked the water outlet and did not find any salt clogs. The [Mercury 90-HP FOURSTROKE] did shoot out a good stream for a few seconds--then almost nothing. This pattern continued for several minutes while I ran the [Mercury 90-HP FOURSTROKE].--Steve

[Phil T]

While a bit stumped, I would go back to the basics.

- Check the hose and muffs. When I first turned on my garden hose, there was a lot of air. I would bleed off the air before adding the muffs. Sound plausible.
- Have you had a frost or freeze? Ice blockage or hole in the hose?
- Hose on full blast with any shut-off valves open.

If you hook it up to the boat again, does the problem re-occur exactly the same?

[Jefecinco]

Not all muffs are equally effective. Last year I replaced the Sierra brand muffs I was using because a lot of water was leaking out around the muffs and I was annoyed to find if I wrapped a bungee cord tightly around them they did much better. I purchased a Mercury brand muff which, while doing better, is not perfect.

Even after doing a seasonal water pump replacement the tell tale discharge is tepid. I found the cooling water flushing arrangement on my old Evinrude FICHT to be much better.

[howlingdogsteve]

Thanks for your thoughts guys.

We live on Long Island and the weather here has been swinging like a pendulum, but, the garden hose was stored indoors and the [cooling system of the ] Mercury 90-HP FourStroke EFI engine was drained when the 2003 170 Montauk was hauled out about a week ago. Very doubtful either had frozen water in them.

We have had this boat and Mercury 90-HP FourStroke EFI engine for 10 years. I perform all mechanical work on it, so I have a good idea of all the baselines of the motor (as mentioned above). I'm using relatively new muffs--the brand is Attwood, I believe--that seem to be fine. In the past, the Mercury 90-HP FourStroke EFI engine put out a reasonably strong confidence stream (10-PSI at 1000-RPM) while on muffs; that is quite similar to in-water performance. After some detective work today, I believe that the super-thin hose going to the water pressure gauge may have a blockage. This should not affect the actual engine flow, should it?

Unfortunately, the weather blew in pretty strong this afternoon which precipitated a hasty retreat indoors.
Any other comments or ideas would be more than welcomed.

[jimh]

If you are suspicious of the water pressure gauge reading accuracy because the small-diameter hose that connects the pressure sensor to the engine's cooling water system might be blocked, try disconnecting the hose at the gauge. If the hose is unobstructed, water should soon be flowing out of the hose at the helm area. This is one way to flush the hose, too.