Since the purchase of the boat, engine maintenance has been centered around ensuring the oil and filters are changed twice a year; at the start and at the end of the season. The oil lines and hoses are of unknown age and the service history is unknown. One of the troubling issues has been the tight 90-degree bend of the oil line from the center of the oil filter to the engine block. Both engines are configured this way.

Oil lines as installed. Notice the tight 90-degree bend of the line coming out of the filter base

A few of the other lines are showing signs of fatigue and wear, especially one of the transmission cooler line on the Starboard engine. Wanting to be proactive, I decided it was time to replace all the lines. The folks from American Diesel Corporation suggested that in addition to new lines, I should upgrade the size from the current 3/8" lines with the next larger size 1/2" lines. ADC has the lines and they are cut to the lengths required. The shortest 3/8" line was 13" in length, ADC adds a bit to lessen the tight radius. I ordered two complete kits. One thing that they did say is they were going to provide the diagram for the correct oil flow.

The ADC diagram is here as a PDF.

When I finally got around to starting this project I didn't think much about the diagram they provided. After all, how hard is it to replace some oil lines? You do one engine at a time, one line at a time, no big deal. Right!? Starting with the Port engine, I took off the first line, from the cooler to the block. I grabbed the first new 1/2" line and tried to put it in. I was shocked to find that the line was a bit short. I couldn't believe it. Could the guys at ADC have made a mistake? I broke out the diagram they supplied and much to my surprise, the oil lines as plumbed on my Port engine were absolutely backwards from the diagram I was holding. I was stunned. The engine run fines, great oil pressure, so I know that it works as-is. I thought maybe the Port engine was a one-off problem so I checked the Starboard engine. Sure enough, it was plumbed just as the Port engine. Now what?

This is how it should look (image proved by American Diesel Corp)

So what to do? If I correct the flow, will it make things better? Will it break anything? I posted the questions to the Grand Banks Owners Forum and the responses pretty much were what I expected: "Make it right", "Don't change the flow if it works as-is", to "Just make sure you get the lines right, otherwise you can burn up your engine." Well that was a lot of help;-) I contacted Bob Smith of ADC and he provided great insight and advice (on a Sunday none the less). Bob assured me that I should make it right and if I follow their diagram and the castings on the engine and filter housing, I would be fine. The rationale for the oil flow is to filter the oil hot, cool it, then return it to the block. My setup was completely backwards. Bob also indicated that this setup was often done as a result of American Marine doing the final assembly of the engines, not Lehman. The other key suggestion Bob made was to replace the oil cooler since the flow was backwards for so long that reversing the flow would end up pushing oil through and potentially sending contamination INTO the engine. Oil coolers are cheap compared to an engine rebuild. Seems like reasonable and prudent advice.

I wanted to double check the castings to convince myself that this is the right thing to do. The oil filter and block castings are just as ADC indicated and are shown below:

Block oil line connection	Oil Filter Base (inverted)

Now that I know the castings are correct and marked as expected, it shouldn't be too much trouble to get it right with the diagrams and pictures that ADC supplied.

Check back in a few weeks after I get it all assembled....