Mariner 75

[wizard]

Just need a little direction, I have little understandings of engines and been rip off a few time with people who say they know about engines, so I'm hoping for a bit of advice from anyone. I have an oldish Mariner 75hp, that up to Friday has been fine, I was traveling at about 6mph when I heard a large clump, first I thought I had hit bottom but this was not the case as prop was fine and dept finder, showing plenty of water, the engine was very hot, I had oil in and when I left the harbour it was showing, that it was pumping a good amount of water through.
I have checked the prop which rotated when out of gear, when in gear it will only allow me to move the prop so far one way and back again, we manage to free it a little when I took cover off to see it I could move top with a large socket again it allowed me to turn it 3/4 away around and back again, I was told the piston were moving, we also took the plugs whilst we done this, when we tried to restart with key it would just turn the engine the 3/4 of the way around, before I pay out on this, has anyone got any idea.

[Russ T Hinge]

When in gear the prop should only move in one direction, it would not be of much use were that not the case, it can be moved very slightly in the other but not much.
After the noise did the engine stop ?

[alana]

if you cant turn the flywheel freely ;out of gear; the motor has internal damage.

[Russ T Hinge]

You say it has oil therefor I assume it is a four stroke ?, from your post I would say a valve has dropped.........

[JPM]

The first thing I would do is drop the leg and check how the prop turns when free of the power head , if it runs fine in gear then I think your next job will be to remove the head and have a look at the pistons


PS welcome to the forum ,,,,,,,,,

[Russ T Hinge]

Take off the rocker cover and check the valve train it may be a broken cambelt ?, then remove the plugs and engage the services of a good torch.......

[wizard]

Its a 2 stroke engine, it did just stop, I shall take it off this week and get someone to look at it from the club I belong too, thanks to everyone who took the time to reply.
I think I might have to look at another engine, I needed a smaller and newer one, but I didn't want to replace it just yet. More worried about telling the Miss:

[JPM]

The same happened to mine last year . My outboard started to slow down then stopped with a clunk , the slowing down was one of the bigend bearings disintegrating, the sudden stop was when a bit of the bearing got stuck between the exhaust port lip and the top of the piston , This is what I found when I took the head off mine
To cut a long story short I fixed my outboard , and it is now running fine, most of the spare parts I got off ebay ,



full story starts post 494 HERE
PS welcome to the forum

[alana]

did the oldish mariner 75s have a cylinder head that could be removed. mine circa 1989[date could be way out] was blind bored

[wizard]

This is the only photo I got of the engine, I am only guessing the year, from info that I had when I brought the boat may be later( engine number 4322943) but I'll get a couple tomorrow of it and post it then.

When we tried to turn it, we removerd a black cover that was protecting a round disc with a large bolt in middle, this may be what you were talking about?