115h Merc 300hr Service

[BLing]

Hi guys,

I have only put 100 hours on my engine since my last 300 hour/3 year service and had the impeller, thermostat, etc all changed as per
factory recommendations.

As stated above, it has now been 3 years but only 100 hours. Would you guys still do the impeller and all the additional recommended work? Every year I do my oils and inspection, etc.

My couple boating friends said they would not change out the impeller and wait until your closer to 300 hours.

Motor is running strong and has a strong stream.

Thoughts?

 

[salmonkiller01]

Time or hours on an impeller. I would change it out. They are rubber and wear/age although you will look at it and it will look good. More of a peace of mind. Just did mine on my 150’s and it is an easy job on mercs

 

[Aquaholic]

Is there a service shop that you have a relationship with? It’s really your call, but just remember that the impeller is always in a twisted contorted position where there’s stress on those flukes or webs, and that’s often where the cracks start. My 115 is due now for a 300 hour service, however, I use often, so the years and the hours are in sync.

 

[Macdeep]

Ya piece of mind = change it.

But also sure you can run it another year…

Small chance, but big consequence.

I’d do it on schedule (300hrs or 3 yrs) if it were me.

You can easily check and/or change your thermostat, plugs, and fluids yourself, then decide if you want a pro to do the work or take care of it on your own

 

[scott craven]

If it's still pissing water good, give it another 100 hours.
I've had impellers last 500 hours easy.

 

[zurk]

buy the parts and keep it onboard. if you need it, its there.

 

[BLing]

Thanks for the input gents!

 

[sly_karma]

If it's still pissing water good, give it another 100 hours.
I've had impellers last 500 hours easy.

Install a water pressure kit and put the data on the MFD along with engine temp, fuel burn, charge voltage etc. Observe water pressure as time goes by to see changes that indicate impeller is getting tired. Eg, it used to make 10 psi at 1200 rpm, now it's only 8.5 psi. And so on up the rpm scale.

 

[Max123]

A water pressure kit is great to have. I had one installed on my last motor, and really wish I could put one on my Etec (I think its possible, but haven't had a chance).

Impellers fail catastrophically if you run them dry, but in the absence of any bone-headed dry starts they will fail gradually and will be visible on the pressure gauge.

Regarding your general question - I personally think the answer depends on whether it is a fresh or salt water boat and if it is moored.

If moored, or used in salt water I would definitely stick with 3 years - you just want to get in there and make sure the fasteners don't freeze up, and add grease to the shaft splines. The water pump is just the excuse to open it up and inspect everything.

For a trailered boat used exclusively in fresh water, I'd be a little more lenient. Growing up we had an old mercury Tower of Power 115hp that we bought used in about 1988. We changed the gear oil annually, but never changed the impeller - didn't even know what an impeller was. We gave the boat away in about 2015ish, with the original impeller still running happily. Same with an old 9.9 Evinrude that was even older. Both used exclusively in fresh water.