Fuel consumption 1964 Mercury Kiekhaefer 850

[RMasters]

Hello all,

We bought a boat a few weeks ago and now found out what kind of motor we have, one of what is being called the "tower of power", an inline six with 85 hp.

A true antique like our boat, a 1983 Baja 16SS. But, here is what we try to work out with the motor.

It is a monster, has full compression, but consumes excessive fuel. It smells a little bit like gas when you run it at idle. I guess you can't really smell it when you drive, right?

Anyhow, on a 630 acres lake, we were able to go across twice and did 1 run around the entire lake (at about 25% power with occasionally bursts), and our 6 gallon tank was almost empty.

We check the obvious items already, tank, bulb, lines, but couldn't find anything wrong or leaking.

We will take it to the Mercury dealer next week to have it checked out thoroughly, just wanted to see if someone else has one of these engines, and what they experience with it. BTW: Mercury supplied us with a free Operator's Manual for the motor, in PDF format. It covers all 2, 4 and 6 cylinder models with full gear shift as well as the 2 cylinder automatic transmission. It shows you basic maintenance (like fuel filter cleaning etc.).

The best part is that we don't have a fuel gauge in the tank (it's a 1964 Kiekhaefer Mercury steel tank), so we have to stop every 15 minutes or so and check. Not very convenient.

Thank you for any input.

Greetings!

 

[Fuzzytbay]

Re: Fuel consumption 1964 Mercury Kiekhaefer 850

In general fuel consumption will be 8.5 GPH with that motor. Those motors get best fuel economy around 75% throtle. I find on my 61 800 FGS that low speed use's nearly as much fuel as 75%.

 

[RMasters]

Re: Fuel consumption 1964 Mercury Kiekhaefer 850

Thanks FUZxxxx, that helps a lot. We just ran across an "old" Mercury technician, he told us that these motors burn 10% of their horsepower, so 8.5 is right on.

Any tips on how to define 75% throttle? At full throttle, our lever is horizontal. We have to move it from vertical (idle) at least to a about 10 to 15 degree position before the clutch engages, and then another 5 to 10 degrees before rpm increase.

Technician says throttle cable is fine, properly routed and adjusted, carbs open completely at full throttle.

Thanks!

 

[RMasters]

Re: Fuel consumption 1964 Mercury Kiekhaefer 850

Well, here is an interesting update. By now we even met people working on these old engines, and we were told that not a single one of them ever heard of the 10% formula.

We know had our carburetors cleaned and new floats installed. Ran the boat for 1 hour including going high speeds up and down the lake (always above 40 mph). Then topped it off again.

Fuel consumption was about 4.5 gallon, that's all it took. Went through a channel and cruised slowly on the shoreline (looking at houses), 1 hour goes by and we checked, took just a little over 3.5 gallon.

I used a little trick and got to talk to someone from the Mercury Classic Hotline for free, they even emailed me the original manual which contains quite a lot of information about adjusting and maintaining this motor. Thanks Mercury!

Keep your engine properly maintained, it works "wonders". Ours runs better than ever now (to at least the extend we can tell).

Ahoy!