Feelings on '95 mariner 100hp

[81 beachcomber]

Looking at purchasing a mariner 100hp 1995. Rebuilt (apparently) as the injectors failed and now just runs it pre-mix to avoid them failing again. Any thoughts on these motors? I am going to do a compression test and test run when i look at it, just wondering on other peoples thouhts on these motors or any problems others have encountered..
Cheers

 

[sschefer]

Re: Feelings on '95 mariner 100hp

The 100hp Mariner is a 2+2 motor. The engine is designed to run on 2 cylinders up to 1800 RPM then two mechanical pressure operated check valves open (similar to injectors) to add fuel to cylinders 3 and 4 so they can support combustion. The opening is assisted through the use of a single accelerator pump.

The motor is sold as the big motor that could troll all day and get up an go on a moments notice.

When running below 1800 RPM, the carbs on 3 and 4 supply adequate fuel/oil to lubricate but not support combustion. There are no traditional crankshaft sealing rings so oil does tend to accumulate in #4 cylinder if the engine sits for a long time.

The weak link in these engines is the lower unit. When the engine turns on at 1800 RPM it is like hiting the nitrous and the small (4-1/4") lower units don't seem to hold up well under that sudden burst of power when the prop is already hooked up. The 3 dog clutches tend to wear more than with other engines.

The solution is to run a vented prop and allow some extra slip/blowout. Some folks grind the ridge off the top half of the lower unit rear hub to help with this also. That ridge is known as the blowout ring. On most motors you don't want blow out but on this one it might help to prolong the life of the lower unit.

In 1992 they changed the exhaust diverter plate to an upgraded design that seems to hold onto the gaskets better. Prior to that they were prone to blowing the gaskets, warping the diverter and allowing water intrusion that usually showed up as a super clean #4 piston.

You mention that then injectors were removed and I take this to mean that the oil injection was removed. If it was done properly with the correct conversion kit before it failed then you're o.k. More often than not the pump fails and the damage is done but the only repair was to disconnect the oil lines and go to pre-mix. This type of fix is a disaster waiting to happen.

All in all it's a good motor but I wouldn't call it great.

 

[81 beachcomber]

Re: Feelings on '95 mariner 100hp

Thank you very much for your reply, lots of good information. This 2+2 system seems pretty complicated, is it often that those check valves for 3+4 fail?

Also he has "said" that the injectors failed THEN the motor was rebuilt and ran on pre-mix.. is there any way of knowing for sure if it was.. other than doing a compression test?

Anyways thanks a lot for your reply, very helpful

Cheers

 

[sschefer]

Re: Feelings on '95 mariner 100hp

Hard to say what he meant by injectors. I'm going to have to assume that its a reference to the oil injection system since you're now running pre-mix. It's also hard to know if it was done right or not. The pump needs to be removed and the correct Merc block off kit, O ring and bolts installed. It's easy enough to do but often not understood.

The other two mechanical injectors are a regular maintenance item. There is a 1/8" inline fuel filter that sits behind the oil tank. NOBODY every realizes it's there and so it never gets changed. Serviceing the mechanical injectors is a little time consuming and not something a novice would attempt. It requires removal of the electrical plate so if you're not intimately familiar with the wiring of this motor you probably don't want to attempt it. Usually SeaFoam or other Fuel treatment like Merc Quickclean is enough to maintain them.