Troubleshooting

We have spent the last two and a half days attempting to find the cause of the overheating engine and believe we may have found an answer. On Wednesday afternoon George noticed that the seawater pump intake hose starts to collapse—flatten—when the engine runs over 1500 rpm. 

Video of seawater hose collapsing at higher rpms. It is especially noticeable when the engine is turned down to neutral. 

Although we aren’t engine mechanics, we both thought that wasn’t a good sign. We have since confirmed that the hose is not supposed to do that and have focused our efforts on finding where there might be a restriction in the flow of water that causes the hose to collapse. 

The seacock—opens and closes to allow seawater in—was an obvious suspect. Things can grow in the seacock or debris can get sucked in.  George borrowed a high pressure hose nozzle from Dan and used a hose to spray water from the inside boat out through the seacock. That made no difference in the collapsing hose. He then disconnected the hose from the seacock and ran the engine using water from a bucket. The hose still collapsed when running the engine, but that indicated the problem was not with the seacock. Nevertheless, we hired a diver to look at the saildrive to see if there were any obvious obstructions to water entering the saildrive. The diver said everything looked good. George disconnected all hoses and inspected the hoses, fittings, and seawater strainer. He saw no visible obstructions. We inspected all hoses for kinks and found none. 

We have been communicating with Mack, our Maryland mechanic, and he had us show—via FaceTime—the seawater system as it goes from the seacock to the pump. He suggested that it may be possible that the fitting he fashioned to connect the 3/4” inch hose to the 1” hose may be causing the restriction. Today’s project was to buy hose and fittings to bypass the 3/4” inch hose and conduct another “bucket test.” It took a while to buy what we needed and get it set up but it appears that the hose no longer collapses. Fingers crossed we may have found the problem. 

Next up—reconnect all of the hoses from the seacock, through the strainer, and the pump—but with a smaller, temporary 3/4” to 1” fitting. If the hose does not collapse we will replace the fitting with a more permanent fitting that we have on order. 

Video taken without the 3/4” hose—and the potentially problematic fitting— attached. It does not appear to collapse. 

Old fitting that was replaced. Although it was quite corroded it is smaller than the new one down below. 

New 3/4” to 1” hose reducer. The 3/4” hose is on top. The 1” hose is removed. The parts are bronze and quite beefy. 

The 3/4” bronze and is on the right. The walls are quite thick so make the inner diameter of the fitting smaller than the brass one on the right. It is possible this restricts the flow of water enough to cause the problem. 

Setup for today’s “bucket test.” The 1” hose on the right is just an extension to fit in the bucket and attaches directly to the 1” seawater pump intake hose. The hose on the left refills the bucket as the engine runs.