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I am looking at two 17 ft. Montauks that have 100hp. oil injected Merc. outboards for possible purchase. They have the oil tank on the the motor with the sight glass. I am wondering if these were good motors and what i should look for during inspection. Thanks in advance.

Drew

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This is the lowest HP version of the 4 cylinder 2 + 2 engine, that certain people love to run down. The engine can put out as much as 125HP, it's best version, and it's actually a pretty good engine. It idles on 2 cylinders as the carbs on the other two cylinders have no low speed jets. As RPM's approach 1800, the other two cylinders cut in.

This 100 HP version of the engine was discontinued somewhere in the mid 90's, as Mercury increased the displacement of the 3 cylinder 90, making it very close to an actual 100HP, so this model was no longer needed in the line.

If the Whalers are nice, I would not let this engine keep you from buying it. I have no direct experience with one, but I hear they run strong.

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I do not know of anything particular to those motors except to tilt it up all the way with the cowling off to see if the oil tank leaks out of the fill cap. They can be a pain like that.

Other items to check on any used outboard are:
Visually inspection does the motor look cared for or abused?
Does the owner have maintenance records?
Check for any obvious leaks, missing or loose parts etc...
Run a Compression Check. All cylinders should be within 15 psi of each other.
Inspect all wires and fuel lines for signs of damage or insulation loss.
Inspect the propeller for damage.
If possible remove propeller and inspect the shaft and drive seal for signs of damage.
Remove a little gear case lubricant check for signs of water (i.e. is it milky).
If it is able to be run in the water that's great/ Absent that run it in a trash barrel full of water.
A motor that stays at a high idle may be hiding something (it will also be hard to shift in to gear).
When it is running check for a good pee stream. Stick your hand in the pee stream to see how hot it gets.
Shift it in to forward and reverse (does it shift easily). Note check shifting with engine off or with prop off.
After running it with the gear case immersed in water check the gear case oil again.

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I do not experience with this either... Fishmore has made good points as check list. I will say that I see many of those 4 cyl engines around stating with the old clam shell cowl design. I am fairly sure the 100HP was made until 2000/2001.

I did have experience with a V6 mid 80's Merc. It was very a solid engine. The one thing I would add is to check the oil hoses (all hoses) for pliability. If they get stiff they will crack and that spells disaster if it happens while running. Had mine replaced on my 90 Yamie.

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I just brought back to life a 1994 115 Mariner 4 cylinder 2+2 this summer. It had been sitting on the back of 1963 Currituck idle for 4 years in a neighbors yard. I bought the boat, motor and trailer for $1000 from the original owner. I was thinking the motor was going to be junk. But after finding out the compression was good. My mechanic informed me that I should replace the following items: the switch box, stator, wires, rebuild the carbs, fuel pump, water pump, in-line fuel filters. That is all it took. The motor runs great and has been reliable for the 50 hours I put on it this summer. I gets lots of people that stop me and comment that I have a "tower of power" on the back of my boat. The boat is a hot rod and is lots of fun. Best of luck.

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Thanks for all the great replies.

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Interesting concept, wondering how those 2 cyl's get lube at low RPM's?

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They don't. I was told that gasoline has enough lubrication to allow no damage at low RPM. I called the owner and he brought it up about this outboard. He said you could idle in if the alarm went off.