Practical Boat Owner – June 2019

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Practical projects

The trouble began when I

bought a rowing dinghy to

use as a tender instead of a

borrowed sailing club dinghy.

Our trusty 1980s vintage

Mariner 2hp outboard engine

hadn’t missed a beat in the

nine years we’d owned it -

but after a season sitting,

unused in my garage, I went to

pull the starting cord and

nothing would move – it had

seized solid.

These engines are simple

beasts, and with nothing to

lose (a 1980s engine doesn’t

around the cylinder head. The

cylinder and piston was the

most likely cause of seizure, so

it was time to look here.

I removed the recoil starter

and the fuel tank and set it

aside, to gain access to the

cylinder head.

Four bolts later (one sheared

off, but the stud later came out

with the help of a large pair of

mole grips) and the head

Unsticking a seized outboard engine

Ben Meakins revives a neglected old 2hp Mariner motor

really owe us anything) I

started to take it apart.

First step was to remove the

cowling and faceplate. This

exposed the powerhead of the

engine. There wasn’t much to

see here, no visible rust –

except for some salty deposits

With the head removed, rusty liquid in the

cylinder shows why the piston was seized

Having cleaned the area completely, the

piston head was soaked in penetrating

oil for a week. A few taps with a softwood

punch then got things moving again

A large screwdriver used as a lever on the

flywheel to get the engine turning again

The piston finally moved all the way down

Cylinder head and engine block flatted

back ready for reassembly

Brand new gasket: note 2hp Yamaha parts

are interchangeable for this model