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Mariner 25hp 0D003174

T

trynhooker

Regular Contributor
I've tried everything I can think of on this one. When I get it started it runs a few seconds, even sometimes up to almost a minute then dies.
The carb had been cleaned twice, injector rebuilt, carb float set correctly and fuel pump rebuilt.
The electrical resistance checks all good, had to replace both plug wires.
Can't get it to run long enough to put the meter on it to check power but it does have spark on both cylinders.

This is what I think may be the problem, however there is no way to prove it other than replacing it.
On the bottom of the carb bowl, you can see where someone put a grinder across it. No idea why that was done cos even if the gasket setting area was nicked the would have been no reason to grind such a big area.

So I'm wondering if that area has somehow messed up the designed specs of the main jet. Like it is now maybe too close to the inside tube.

Any thoughts?
FYI, I am a marine technician but this one I just can't figure out.
 
Most importantly what is compression? Those motors do not like being overheated. Did you check the ball and spring under the primer? The ball can sometimes get jammed into the spring and cause the motor to flood. Is the base gasket for the carb on correctly? If it is backwards it will cover the pulse port for the fuel pump. Are any of the plastic bits broken for the primer and high idle assembly? If anything is broken it may not allow it to high idle for warm up. I bet the grinder marks are because somebody ground off the nub that holds the primer/bracket assembly in place. Is the link and sync correct?
 
1. Compression was 105/110.
2. The primer was rebuilt and when I first took it apart the ball wasn't stuck in the spring.
And I've taken it apart more than once to recheck everything and it still was never stuck.
3. Water pump impeller was renewed also and has great flow running in water tank.
4. Someone did some backyard fixing on the motor as well. One of the tiller cables was cut but other cable does work properly. It is a tiller handle and side shift model so the tiller handle doesn't shift gears.
5. It is missing the high idle wire but the primer bracket is there and works properly, and the tab was not ground off so no idea what they were doing just throttle.
**6. Since you mentioned it I will have to check the carb gasket as I don't recall checking it since I never took that gasket off. That very well may be an issue!!
7. Sync/Link. I don't have a Mariner manual only the Mercury manual. Many things are identical but the Mercury book doesn't have any pictures of this type linkage.
However, the throttle plate is closed with no throttle applied, and at full throttle it stops in the horizontal position where it should be.
Other than that, the sync is limited to adjusting the timing link
 
The tiller is supposed to have both cables because it is a pull system. Changing it to a single cable is a safety issue. Did you put a complete rebuild kit in it od just replace parts? A complete kit would have had a new base gasket. What is the low speed mix screw set at? Those i like to start at 2 turns out.
 
Agree on tiller, it's the way the guy brought it over.
Mixture screw was tried at all settings starting at 1 turn out to 2 turns.. nothing really changed unless I turned in less than 1 turn which of course would not allow enough air pass.
I haven't checked carb gasket yet, hopefully today.
 
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