Get the lead .......IN!

[NW Redneck]

I have a 1975 OMC 175 (ford 302) My owner's manual
says to use leaded fuel ONLY.

1. From what I've read the lead is to preserve the valve seats. Will running mid grade unleaded harm my valves/engine?

2. Is there an additive available anywhere I could use?

After all that work to get it running I don't want to burn it up after just a few hours! Thanks!

Colin

 

[calwldlif]

Re: Get the lead .......IN!

Lead has been gone for a long time.
What prompted this worry?
There is always debate.........:%

Some say there are other ingrediants that
accomplish the same thing.......

Some say you need to add something...:'(

The problem I believe is exhast valve burning :'(

I would (if I were you) worry more about
octane 8)

It would not hurt to add a snake oil to the gas,
Anything form ATF to Simulead Substitute
8)

 

[bruceb58]

Re: Get the lead .......IN!

1974 was the first year of catalytic converters on Fords so yours could easily be hardened seats.

Hopefully, it was just an octane requirement which you can get by with adjusting timing or using a mid grade gas.

In car engines, the switch from leaded to unleaded often doomed the valves in around 25k Miles. Not sure how that would correspond in a engine in a marine environment.

 

[NW Redneck]

Re: Get the lead .......IN!

This boat is new to me and is the first I have had that requires leaded fuel. So you would recomend a premium/high octane gas? Or an octane booster like 101+ octane boost?

"175 AND 190 HP engines must use leaded automotive fuel of 89 AKI Octane or higher. "

This is straight out of the manual. It also calls for leaded fuel for 120 and 140 HP engines.

 

[Boomyal]

Re: Get the lead .......IN!

Not sure exactly when the cutoff date was. I would like to know that myself.

The difference between lead and post lead cylinder heads were simply the hardened exhaust valve seats. Octane does not play into this equation even though lead was an octane booster. As far as lead relates to the valves and seats, it acted as both a cushion and a coolant on the unhardened iron valve seats. There are lead substitutes available. I do not know how effective ther really are.

I don't believe the valves themselves were any different.

 

[Bondo]

Re: Get the lead .......IN!

From what I've seen,....... Most motors Die from Neglect,... or a Good Hard Freeze,....
Long before the Valves suck up into the head far enough to be an Issue........

If by chance I had a Head off,+ was having work done on it,....
I'd probably spend the money for New Seats......
Or,......
Just Update the Heads......

 

[calwldlif]

Re: Get the lead .......IN!

I am surprised your octane req'ts
are 89. This grade is still avail.

Lead was an octane booster by COOLING
the charge. Its properties allowed valves
to giveup heat to the head. Cushioned too.

The biggest diff between lead/nolead
is the operating temps the fuel is run at.
Leaded days 160 was norm.
The unlead put the range to 180-190.

In my OPINION the exhast valves are the first
to have trouble, burning, seat damage and
warpage. In cars it takes time if you putter around
and never make the engine work.
In a boat the engine is often worked hard.

These are the facts as I believe them
to be.
You make your own call

 

[NW Redneck]

Re: Get the lead .......IN!

Thanks for the replies.

calwldlif- With the unleaded I'm running @ 160-170*F. (160* t-stat) Do you mean the unleaded burns hotter, or the engines were designed to run hotter?

Anyone ever use an additive? If so, which?

Thanks again.

 

[rodbolt]

Re: Get the lead .......IN!

valvetane is what we use on older engines. somewhere merc has a chart on what engines use a lead or lead substitute additive.
but the local towboat US capt runs it even in late model engines so I guess it does ok.

 

[69slickcraft]

Re: Get the lead .......IN!

their was no unleaded fuel in 1969, that was one of the first things i noticed on my boat it ran a bit off then i started putting lead additive in with premo gas runs great ever time, I prefer lead additive over lead substitute. but the tubbers dont,

 

[Tail_Gunner]

Re: Get the lead .......IN!

SImple answer here, Believe it or not lead acts a lubricant unleaded would or could cause premature valve train wear.

Just use Marvel mystery..............8) Or go to Napa and look for a lead substitute..............If that motor has gone this long your not in any danger..oo