Lower unit issue

C-Wolfe · Posted: Sat Oct 15, 2022 3:35 pm Post subject: Lower unit issue

Got some issues with my port engine lower unit on my last trip. Water was a little choppy so had to slow down some but could still keep it comfortable going about 15-17 MPH. They was a sudden change in engine noise and a reduction of speed. I set the engines in neutral and while raising them, my buddy saw a small branche floating away from the port engine, we could not find anything else so we resume our trip. I could barely make it on step as if I was getting thrust from only one engine. It was getting dark and we were only a couple miles from our destination so we limp along on the good engine.

On the next day, I tried to find the problem, both prop spin freely in neutral with no grinding noise other then a bit more play and a small "click" on the port one. both locked up normally while in gear. I remove the port prop and did not find anything abnormal so I put it back, the extra play and click was gone. I fired up the engine and give it a try, it all acted normal. We made it back on both engines with no issues.

I have removed the lower units and will be draining and inspecting the oil in the next few days, but would like to know if I should be looking into anything else.

Thanks for any help and advise.

srbaum · Posted: Sat Oct 15, 2022 3:45 pm Post subject:

C-Wolfe,
Maybe the hub of the propeller has spun out. When this happens, the prop will act normal when checked by hand and will also idle pretty normal. When you increase speed, the prop will turn, but will slip and the prop will not go up in RPM, while the engine still can.

C-Wolfe · Posted: Sat Oct 15, 2022 3:55 pm Post subject:

T.R. Bauer · Posted: Mon Oct 17, 2022 10:52 am Post subject:

Weird. It is possible that some debris was keeping the lower unit from engaging. The threaded rod that shifts the lower unit into gear must be able to move freely. As far as the spun prop suggestions, it's a good one, but spun props (and I've had a couple on different boats) will provide some thrust to a certain threshold and then slip like hell. I've never had one go back to a normal state. Obviously, an easy way to check would be to just trade props from port to starboard as the problem would move with the bad prop.

Another thought is that when you hit whatever junk that caused the engine to cavitate and raise RPMs made the REV limiter to engage which would give you little to no power....limp mode. If you have older engines you don't have that, but the newer EFI ones do.

C-Wolfe · Posted: Mon Oct 17, 2022 12:56 pm Post subject:

[quote="T.R. Bauer"]Weird. It is possible that some debris was keeping the lower unit from engaging. The threaded rod that shifts the lower unit into gear must be able to move freely. As far as the spun prop suggestions, it's a good one, but spun props (and I've had a couple on different boats) will provide some thrust to a certain threshold and then slip like hell. I've never had one go back to a normal state. Obviously, an easy way to check would be to just trade props from port to starboard as the problem would move with the bad prop.

That is something else that cross my mind, got knock in neutral and keep enough pressure to not re engage completely. I had the engines lifted out all night so whatever it was could have fall out.

Another thought is that when you hit whatever junk that caused the engine to cavitate and raise RPMs made the REV limiter to engage which would give you little to no power....limp mode. If you have older engines you don't have that, but the newer EFI ones do
I got Honda 2007, last year of carbureted engine for them. [quote]