Yanmar 1GM User Manual page 55

OP ERATlO:-l. L UBRICATION. MAINTENANCE AND TUNE-UP 49
outer belt),
it
is a good idea to replace al l belts as a set. The
added expense is small compa red
10
the cost of replacing
the belts indivi dually, and rep lacing each belt reduces the
possibility ofa breakdown on the water , which could cost
far more in time and money.
Make sure the dri ve be lts arc properl y tensioned at all
limes. Ifloose, the belts will not drive the dri ven compo-
nenrs at ma xim um efficiency. The be lts wil l also wear rap-
idly beca use of the increased friction caused by slippage.
Bells that are too tigh t will be overstressed and prone to
premature failu re. An excessively ligh t belt will also e ver-
stress the water pump or alternator bea rings. resulting in
premature failure.
Alternator drive bell udju.\lme lll (mo dels equippe d with
seawater coo ling)
1. C heck alternato r dri ve bell tension by depre ssing the
drive belt at the midway po int on the belt (A. Figure 11).
The be lt sho uld defl ect approx imately 0.4 inch (10 mm)
with moderate finger pres sure .
A
2. To adjust alternator dri ve bell tension, loosen the alter-
nator retaining nuts (8 , Fil:ure 12), then reposition the al-
ternator. Retighten the retaining bolts and recheck be lt
tension.
A lternator drive belt adjU!ilmenl {models equipped ....ith
fresh ....ater cooling)
The alternator drive belt also drives the freshwater cool-
ing pump on engi nes so eq uipped.
I. Check alternator dr ive be lt tens ion by depressing the
dr ive belt at the midway point on the belt (A, Figure 13).
The belt shou ld deflect approx imately 0.4 in (10 mm)
with modera te finger pressure .
2. To adjus t alterna tor drive belt tension, loosen the alter-
nator retaining bolts (B , Figure 12), then repo sition the al-
ternator. Retighten the retaining bolts and recheck belt
tension.
Sea ....ater pump drive belt adjU'ifmenl (2G.U. 2G.U20.
3GM. 3GM30. 3H .\f And 311.\ /35 models)
I . Check seawater pump drive belt tension by depressing
the drive belt at the midway point on the belt (A, Figure
14). The belt should deflec t approximately 0.24 in (6 mm)
with moderate finger pressure.
2. To adj ust seawater pump dri ve be lt tension, loo sen the
screws (B, Figu re 14) that retain the water pump mount-
ing plat e. Reposition the plate to obtain the corre ct be lt
tension, then retighten the bolt and nut. Recheck belt ten-
sron.
3