Outboard maintenance

[rednaell]

I use my boat around 15-20 trips yearly during the summer.
I would like to ask outboard owners who use their boat like I do i.e. only in summer, regarding the following:
After how much time do you replace the water pump impeller?
Does the thermostat needs replacement? after how much time if it the case?

[benri]

I think that changing the impeller every 3 years should be safe if you use original parts and nothing extraordinary happens like running the engine dry. I inspect mine every season and if it is still in good condition (stiffness and cracks) I use the same one.
Regarding the thermostat, I remove and clean during the winter however have never needed to change so far.
One more very important aspect to look out for, which most local mechanics don't seem to bother about is the anodes inside the engine. The first time I removed mine after 4 seasons, (after having read the importance on an American forum) I was shocked! Since then I remove and inspect every year and change every other year.

[rednaell]

wow inside engine. I never thought there were anodes inside as well!

[rednaell]

I`v just checked the manual, and it does say the below on page 18

http://www.hedges-uk.com/boat/Merc/outboards/2-stroke/2-stroke/75-90-100-115-125/75-75%20MARATHON-75%20SEA%20PRO-90%20-100-115-125-65-80%20JET%20With%20Serial%20Numbers%20United%20States%20-%200D283222%20and%20Above%20Belgium-%2009793577%20and%20Above.pdf

so I guess that it has no internal anodes to be replaced:

"Corrosion Control Anode
Your outboard has 2 corrosion control anodes. An
anode helps protect the outboard against galvanic
corrosion by sacrificing its metal to be slowly eroded
instead of the outboard metals.
Each anode requires periodic inspection especially
in salt water which will accelerate the erosion. To
maintain this corrosion protection, always replace
the anode before it is completely eroded. Never paint
or apply a protective coating on the anode as this will
reduce effectiveness of the anode.
1. One of the anodes is the trim tab (a) installed on
the gear case. A second anode (b) is installed on
the bottom of the transom bracket assembly"

[benri]

So far every engine i ve seen had internal anodes. Try a web search with your engine name/model. You re looking for something like these:
http://m.youtube.com/watch?v=Qc-TboVRy8Q

[Destination Sea]

yes some engines have anodes inside. I have a 20hp mercury 4s (2014) it has one inside the engine near the oil filter and another two at other points on the motor (not the engine)  the other three engines  all 2s do not have inside the engine but are located outside ex bracket etc such as the etec 90hp.