This photo is part of an ongoing series about removing a Yanmar 2QM20F from a 1979 H37C. It will be replaced by a new Yanmar 3YM30.

It seems that every new H37C owner of a 1980 or older has the same question, how do I check the oil? Or how do I adjust the stuffing box? Well later models had this door in the side of the quarterberth. And it is pretty easy to cut one out in the older models.

I find it totally adequate for the work I have to do. A better option is to cut the door out all the way forward to the corner. Then you can reach the starter and solenoid wiring much easier.

That hot water tank you see in the picture will be replaced while the engine is out.

H37C Q-berth engine access.

This photo was taken with the air cleaner removed(port side) and the heat exchanger removed(strbrd). In this picture you can see the solenoid that solves the start problem that many people have experienced. We call it a relay and there is a wiring diagram of that here in the Photo Forum.

Top of 2QM20

I worried needlessly about this part. The shaft coupler came apart easily. Of course there is the issue of getting the coupler off of the shaft. Worry about that later.

At any rate the engine now sits completely ready to lift out of the boat. There is very little wiring to disconnect. There is the shaft, the exhaust hose, fuel lines, hot water heater hoses, and cooling water. All the parts like water separators(2), heat exchanger, and alternator are safe at home.

The new engine is shorter so will require a new shaft. It has more power and at a different RPM so will require a new prop, a 3-blade Flex-O-Fold. I know, I know but still cheaper than a new boat. A lot cheaper!!

2QM20 tranny and shaft.

In this picture you can see where the main ground is located, right on the back of the engine block. The black wire comes through the strbrd bulkhead from the batteries. The white #10 wire goes through the port bulkhead, across the fuel tank, and to the main ground on the back of the electrical panel.

You can also see the red #4 12volt wire coming from the battery switch across the back of the engine. That wire connects to the main starter post. It also feeds the 12v to the panel.

Just behind that vertical #4 wire and rubber water hose you can just make out a fuse block. It is hard to see from the front of the engine. When that fuse goes(and it will) you have no 12 volts to the start button/key switch.

You can also see a sender unit with a blue and red #12 wires. That is for the tach, gets its signal from the flywheel. This engine will be for sale and comes with complete instrumentation, i.e. all gauges, not idiot lights.

Some Yanmar wiring.