Perkins 4-107

However, this leak continued to get worse and the engine appeared to be loosing about 1 cup of coolant per hour of run time so it was time for a detailed search for the leak. All of the hose clamps were tight which had me nervous (was the coolant loss due to a head gasket or something more serious?), however, there was no coolant in the motor oil, no white smoke in the engine exhaust, and there did not appear to be a leak between the fresh water coolant and the salt water in the heat exchanger. Finally I found a wet streak down the front of the engine coming from the weep hole on the underside of the water pump!

This circulation pump failure provided the opportunity to consider options to upgrade the belt system on Botany Bay. Two upgrade paths were examined: 1) Foley Marine has the bolt up second sheave for the power take off (PTO) of the Perkins 4-107 at a cost of about $200, they have to have a double sheave for the water pump manufactured and have only done so for a 4-108 water pump, luckily it will directly replace the 4-107 water pump (the diameter of the shaft is different the bolt pattern is the same), a new water pump and double sheave is $500, the double sheave for the Balmar alternator is another $50 for a total parts cost of $750. 2) S&W Diesel in Wilmington CA replaces all three of the sheaves with a custom 1" wide serpentine belt (no tensioner required for a simple system) at a cost of $135 for the crankshaft sheave, $115 for the water pump sheave, and $37 for the alternator sheave. The water pump would have to be replaced with a 4-108 water pump to match the diameter of the available water pump sheave (4-108s are far more common engines) for a total cost of $287 excluding a new 4-108 water pump at $105 for a total cost of $392.

However, I had previously purchased a spare 4-107 water pump (without any sheave) which cannot be used with any of the above upgrades and the total increase in alternator performance would be approximately 20 amps at the start of the charging cycle. The cost to have the old sheave pressed off the old water pump and onto the new water pump is $25. Vellos Automotive Machine Shop in Lawndale [310-643-8540] did a very nice job and turned the pump around in less than a day.

So, faced with the choice of $750 to upgrade to double v-belts (retaining a basically stock configuration), $392 to convert to a serpentine belt in a basically custom configuration, or $25 to continue running the alternator tuned back 20% and remain in a purely stock configuration I opted for the $25 solution. This setup has been very reliable over the years (Installed in 1993), is easy to maintain, and did not seem to cause excessive wear on the water pump (31 years is a long time for a water pump to go).

After reinstalling the rebuilt water pump and refilling the system with water the leak appears to have been completely stopped, the engine is again putting coolant into the overflow tank when running hard and returns the coolant to the engine when it is cool. Also the stray "clicking" noise appears to have gone away suggesting that this noise was a bearing starting to fail.

Note that you have to be very careful to fill the engine completely after replacing the water pump, it is very common to have an air bubble in the circuit which won't fill completely until the thermostat opens the first time.

Balmar 912-100 Alternator