First time start up

[Deimus]

I am preparing to fire the motor on the boat I bought for the first time. I don't know anything about the motor condition or when the last time it ran was.

It is a 1968 merc 100hp. Is there any suggestions of what i should check or do before I start it for a hassle free firing?

should the lower unit have the oil changed at a certauin interval?

 

[AMD Rules]

Re: First time start up

Yes, there is a few things that are a must-do before starting that motor.

Change the water pump impeller
Check the timing/sync (see Clams post in the FAQ)
Inspect all wiring
Inspect/replace fuel lines and vacuum lines
Run it a little rich on oil if its been a long time since its last run.
I'd recommend that the carbs be cleaned, and its cheap insurance to replace the needles/seat and gaskets.
Change the gear oil, looking for water and metallic debris. Should be changed yearly, and inspected periodically for the presence of moisture by draining a few drops.

Thats a classic motor, and worth spending a few moments ahead of time to prevent damaging it. You might want to consider checking the compression values before hand to set a baseline for monitoring the health of the motor over time. Shoule be above 100 psi and within 15% of each other in all six cylinders.

Once running, make certain it is circulating water out the telltale, and not running exceptionally warm. You should be able to rest your hand on the exhaust covers when running without fear of scalding. Watch for hot spots near the upper cylinders (sign of poor circulation/venting).

Make sure if running on muffs, that you keep the rpm below 1500. Should idle at 800 rpm or so in neutral.

Visit the FAQ section, as there is a few topics in there that discuss specifically starting older motors that have sat for a long time.

Good luck.

 

[Deimus]

Re: First time start up

how do you change the water pump.? I haven't purchased a repair book yet

 

[AMD Rules]

Re: First time start up

Its not too difficult, provided that the lower unit (gearbox) will drop off without being siezed.

Most time you can just change the impeller, but inspect the housing closely for corrosion/errosion etc. Better to replace than to assume its ok. Gasket kit/impeller/and pump housing are not too expensive.

Here's a good video, for concept. Not a Merc but the process is very similar:

www.themarinedoctor.com

To remove the lower unit:
- disconnect battery cable
- remove the two nuts on the side of the housing, and the one in front
-remove the trim tab bolt (from above)
- with trim tab removed you should see two more bolts/nuts up under the antiventilation plate
- once those are free you should be able to drop the lower unit. Be prepared for it to drop out on its own weight.
- even though you'll be tempted to turn the shaft shaft for fun while you have it off.... don't, or you will have issues upon re-assembly. Its ok to turn the drive shaft though.
- removal of the water pump and impeller is straight forward. Just remember the sequence of removal.
- drive shaft turns clockwise when the motor is running, thus the impeller blades curl in that direction when installed (tips point to the left when viewed from above)
- lube the impeller with dish soap, or light oil to assist with installation
- when re-installing the lower unit, it helps to have an assitant turn the flywheel a bit to engage the drive shaft splines
- make sure to leave the water tube in the mid-section, and to align it in the pump outlet as you re-install the lower unit

Might have missed something.... other's will be along to correct me I'm sure.

/AMD


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