PassageMaker - July 2018

24 passagemaker.com July/August 2018

Troubleshooter

neoprene. Neoprene maintains its elastic-

ity for long periods of time and does not

break down in salt water. (Nitrile will work

if no other option is available but should be

replaced with a neoprene impeller at the

fi rst opportunity.)

Like removing the cover plate, install-

ing the new impeller can be frustrating as

they fi t snugly in the housing. If compress-

ing the vanes enough to get it started into

the housing is challenging, try these tips.

First, identify the method by which the

impeller mates with the shaft. Some rely

on a key, and keeping the key in place can

be tricky. A splined shaft matches up much

more easily. Once you know how it will

align, you are ready to install the impeller.

At this point you will want to use some

lubricant. Some impellers come with a

manufacturer-provided lubricant. In the

boatyards we use dish soap—the soap will

not damage the neoprene, and once you

start the engine you will be blowing bub-

bles out the exhaust discharge, providing

visual confi rmation of your success. The

soap serves two purposes: It helps the

impeller slide into place and temporarily

lubricates it until water fi lls the housing.

(Avoid using petroleum-based products,

such as Vaseline, for lubrication as they

will damage the neoprene.) Apply the

soap liberally to the inside of the pump

housing and to the impeller.

You can compress the blades using a

hose clamp or plastic tie-wraps. Squeeze

the blades and then slip the hose clamp

over the end and slide it up about ¾-inch

from the end. A second clamp or tie-wrap

can be positioned at the opposite end. Now

slide the impeller part-way into the housing

and gently rotate it until it aligns properly

with the key or splines on the shaft. Once

engaged, push the impeller in until the fi rst

clamp stops you. Remove this clamp and

slide it in further. Then remove the remain-

ing clamp and push it the rest of the way in.

The vanes will have to bend one way

or the other, and there is a 50/50 chance

you will have bent them the way they will

eventually go. In any case, the vanes will fl ip

over when the impeller starts rotating. But

on larger impellers (those for an 800-horse-

power engine, for example) it would be best

to get the vanes in the right way from the

start to avoid placing undue stress on them.

WHILE YOU’RE IN THERE

With the impeller removed, make sure to

inspect the remaining parts of the raw wa-

ter pump for wear. Check the inside surface

of the cover for pitting or wear grooves.

The more evenly the sides of the impeller

This cutaway view shows the critical

components: cover plate (2), cover plate

screws (1), impeller (7), wear plate (4), seals (5)

Courtesy JMP Marine

2

(^74)
(^15)