Ugh, what have I bought myself into?

[hise]

Just purchased a boat with what I was told was a 1999 100 hp Mercury..

I didn't know to look at the serial number... turns out there is no serial number plate so I don't know my serial number.

I believe the motor is actually a 1996 because (1) digging around it looks like mercury stopped the 100 hp in 1998 and (2) assuming the starter motor is original, it has a manufacture date in 1996.

Question 1: how can I find my serial number?


The boat stumbles at higher rpms, so I'm giving the carbs a good cleaning.

The carbs are stamped WME-3301, which I assume is called WME-33 on the parts page

www.boats.net/parts/search/Merc2/Me...CARBURETOR-WME-32-32A-33-34-40-40A/parts.html

(well I can't get the url to paste cleanly.... but it points boats.net for Mercury 100 HP, 4 cyl, serial numbers (0D283222 - 0G760299) )

My interpretation of that parts page and my attached carb/jet chart, WME-33 is used on the 115 hp (though my cowling is labeled 100 hp). The jets are the right size for 100 hp engine (though not installed in the right carb)

I damaged a couple of jets trying to get them out, so I'm just going to order 4 new jets; but...

Question 2: Do I order jets for the 100 hp or the 115 hp? (I would like to order for the 100 hp since I'm already at the top of my hp capacity... not looking to be a speed deamon, I just want a smooth ride).

I also believe the engine was rebuilt in the past. Since WME-32 seems to be obsolete, they put in 115 hp carbs and detuned to 100?

 

[ondarvr]

The jets are NEVER what determines HP, jets size is detrimental by what the 100hp needs for the air/fuel mix to run correctly, same for the 115. If the jets are different you will only make the motor run worse by putting in the jets from a different HP motor.

 

[DavidMoore]

The serial number can often be found be stamped into one of the core plugs on the block.

 

[hise]

Thanks for the replies. I have look through the parts lists again. There are several WME-3301s that apply to 100 hp engines as well as 115 hp.. So, I think my concern of mismatched carbs is alleviated. Still you would like to find my serial number. @DavidMoore.. I'm still trying to find that plug... I'm new to servicing my own engine; so, bear with me.... where are the core plugs located and do I have to remove anything to find them? .... On the starboard side of the engine, just below the plate where all the electrical stuff is mounted, there "post" that rises up... about the diameter of a quarter.... I'ts plugged with a black rubber stopper that I'm not sure I want to mess with.

 

[DavidMoore]

Your looking for something like this