Help With Changing Impeller on 1998 Mercury 115 2 Stroke

[JohnMetta]

First off the serial number of my 1998 Mercury 115hp 2stroke Outboard is OG722825. I just got the service manual and read the instructions on how to change the impeller. This is my first outboard so I'm not sure what to expect. My engine is overheating at idle but not when I give it throttle above 1500RPMS. What should the operating temp be? I've watched a couple videos on youtube. I'm thinking I should just change the impeller and not play with the housing or gaskets unless they are in bad shape. Are there any tips you may have for me? Which gear should I put it in while doing this? Any help would be much needed. Thanks a lot.

John

 

[carholme]

Re: Help With Changing Impeller on 1998 Mercury 115 2 Stroke

John;

In the manual, refer to Section 6A, page 8 and see:

2. Shift engine into forward gear.

When you get the LU dropped, do not rotate lower shift shaft, item 36 as seen on page 4 of the same section. Get the impeller out and lets see what condition it is in. Then you can see if the housing or gaskets need changing. If you leave the boat controls and the shift shaft on the LU in the same positions as when removed, you will not have a problem when you re-install the LU. And once you have it re-installed, always check the correct gear shifting as seen on page 36, para 16.

As far as the temperature is concerned that engine will not set off the warning until 190 degrees, See Section 4, page 46.

There is far more information in the manual than you will see from just reading the section titles. I have also sent you the owners manual for additional info.

Gerry

 

[Silvertip]

Re: Help With Changing Impeller on 1998 Mercury 115 2 Stroke

An outboard will overheat at idle if the thermostat is stuck shut. It overheats at high speeds if the bypass valve is defective. Both conditions can be caused by a bad impeller. Neither the thermostat or the bypass valve are difficult or expensive to change.

 

[JohnMetta]

Re: Help With Changing Impeller on 1998 Mercury 115 2 Stroke

Just replaced the water pump kit. Problem still persists. Still overheating at idle. Any suggestions.

 

[JohnMetta]

Re: Help With Changing Impeller on 1998 Mercury 115 2 Stroke

Nevermind. I seems to have worked. Once I dropped it in the water, the water temp stayed at 130.