1973 850 saltwater care and how to not blow a powerhead

[bugelingkayaker]

Well awesome news is that today I get to ask a much different question than I thought I was going to. Kept having issues getting my 1973 merc 850 to run under throttle. Took the carbs out for cleaning again, put in new fuel pump diaphragm and set the idlers and lo and behold it’s finally running beautifully on the water. according to my phone max speed we got was about 33mph
which brings me to the next stage of this which is making sure I take care of it so it lasts as long as possible.
while working on it I noticed there were lots of spare parts on the market from people parting out their motors with blown power heads or thrown rods. On one hand- Yay! I can get parts! On the other hand, got me wondering what the heck do I have to do to make sure *I* don’t blow a powerhead or throw a rod?
so I know the normal maintence stuff, every 100 hours change impeller, change lower unit oil, check for spark on all cylinders, never run out of the water without hose or bucket, but are there any other things I should be checking or doing to ensure I am taking utmost care of this thing? I’ve seen posts relating to other motors saying to always allow them to warm up without running under throttle.
- How long should I warm it up?
-is it safe to run it wide open for any length of time or should I try to always run a bit under full throttle?
Additionally, I would also like to use this in saltwater, but even with rinsing and running fresh water on the clamshells later,
-is this going to be a slow suicide for the motor to take it in salt? Or will judicious rinsing mitigate most of this
-how long minimum should I run it on the hose after use in salt water?
-are there any kind proactive measures I can take to protect against salt corrosion or is care limited to rinsing afterwords?
-anything else I should know, watch out for, or do to make this thing last for years with how I’ll be using it?
thanks for any and all advice.

 

[Scott Danforth]

your motor has steel shafts (changed in about 1978 or 79). so I would not run it in salt water.

running under WOT is what the motor was made for. just watch your RPM's

 

[The Force power]

SD is right!!
They updated the shaft to a graphite-steel in later models, just a FYI some 65 hp model years had the same LU.
so if you ever run into one for dirt cheap; grab it.
I had a 73 as well nice dependable motor!

I don't have experience with salt water, so no tips on that.
The only advise to you to prevent a block failure would be;

Make sure you re circulation hose are clean/not leaking/connected
make sure your timing is not too advanced
Always on the look-out for parts, don't wait until you need them. lol

Remember; she's 47 years old, treat her that way
Let her warm up a bit-- how long? depending on the water-temp she's in. too long she'll carbon up slowly.
(mine never went full RPM until she was warm & not sure why she would not)

 

[Chris1956]

If you can flush her after every salt water use, she will last a very long time, as the salt turns the aluminum brittle, and helps the exhaust baffle and exhaust covers rot out.

Keep the carbs clean, use fresh fuel and keep the water pump maintained. Replace the motor wiring harness when the insulation falls off. Replace the spark plug wires (they screw into the distributor cap), when they start arcing to ground. Do not touch the distributor rotor. It should last nearly forever.

 

[Texasmark]

your motor has steel shafts (changed in about 1978 or 79). so I would not run it in salt water.

running under WOT is what the motor was made for. just watch your RPM's

Slightly off topic but I never could figure that out when OMC and Scott Atwater were using SS way back in the 50's. I was in a Merc dealer once back in the '66 time line and a Merc 90 tower was in for repair. The LU was removed and I couldn't believe my eyes, looking at the drive shaft sticking up out of the LU on and engine used in salt water.

On the question, growing up on the Gulf Coast was the salt water will, not when, attack metals. Having an engine with good corrosion protection and being prudent about your wash out/down methodology after an outing can make the difference, even though sometimes you have had too many beers, or got up too early, or the day was too long and you just don't feel like exerting the effort....you'll pay in the long run.

On my engines, I found that having them setup to run at WOT with the normal load at the upper end of the rating worked best for me. On where I ran the rpms, once setup up properly, that depended on the wind and water. If it would let me, most of the time it was WOT and "When in Doubt, Trim it Out" (Faztbullet quotation).

 

[Faztbullet]

1)

How long should I warm it up? ​

This motor has no t-stat and temp is controlled by restrictions within motor. The colder the water the longer it needs to warm up. Water above 70° need not worry about. Just launch it, leave it running, park and go boating.​

2)

is it safe to run it wide open for any length of time or should I try to always run a bit under full throttle? ​

Make sure engine is propped toward max RPM and not lugging.( I like to see 5200-5400 on older engines) Consistent WOT for long periods will not hurt it.Use a good name brand oil mixed at proper ratio. ​

3) Additionally, I would also like to use this in saltwater, but even with rinsing and running fresh water on the clamshells later,​

-is this going to be a slow suicide for the motor to take it in salt? Or will judicious rinsing mitigate most of this..​

A through rinse of around ten minutes with a salt additive like Salt-Away will help it live longer. The quicker you can get it to a rinse the better off you are as the heat in block dosent have as much time to dry and crystilze the minerals ​

-how long minimum should I run it on the hose after use in salt water? ​

See above​

-are there any kind proactive measures I can take to protect against salt corrosion or is care limited to rinsing afterwords? ​

Through maintenance and losts of neverseize are in your future. Swivel and pivot points a must care for items​

-anything else I should know, watch out for, or do to make this thing last for years with how I’ll be using it?​

thanks for any and all advic​

1) Need to update the "P" hose routing so it routes over top of block. This is to give true water pump output as existing route will allow block to be half filled and still show a decent "P".
2) Change impeller yearly due to grit in salt water
3) Go ahead and pull powerhead and change lower crankshaft seals due to age and future salt water use.
4) Look out for a later model lower unit in 2:3:1 ratio with S/S shaft. ..will need it later on.​