Trojan Boat Forum

I was driving my 74 F25 Express the other day and noticed a noise which may even come and go, but you can feel it in you feet. I just recently purchased this boat. It has the Merccruiser 225 with velvet, but I don't seem to see a dip stick.
Anyway, when the hatch is up I hear what seems to be a slight grind when shaft is engaged at idle speed, but ofcorse hard to hear when closed.
I originally heard this noise at higher rpm when brining it back to down on my maiden voyage. It really seems to come and go at higher speed, but it really feels like a slight cavitation.
REALLY, THIS IS MY FIRST INBOARD SO ANY ADVICE IS APPRECIATED.
Thanks...

Welcome to the forum.

Many here own the F-25 so I am sure someone will be along soon to offer advice.

Mine makes a similar noise. It is really only apparent at around 1000 rpm, and quiets out at slower or higher speeds. I think it is a sort of harmonic resonance- a vibration of sorts, that could be the rudder or maybe the cutlss bearing. I just avoid that speed and in three years it has not gotten worse.

Mine is a bit noisy in reverse, but pretty quiet in forward. Mine is a hardtop, so all the engine/transmission noise is kinda trapped under there.

I have an F-26HT with a 1:1 Velvet drive, Ø1" shaft and a 14x 10 NiBrAl cupped prop. The shaft is straight & balanced, shaft seal is good, cutlless bearing is in good shape & aligned correctly, the trans is in great condition and the flange alignment is within 0.001". All of this being said, I do get noises that you wouldn't get with an I/O boat and it could be mistaken for bearing failure.

When backing out of my slip, I get this noise and believe it's partially caused by turbulent reverse thrust in the shaft pocket under the hull. The rest of the noise I believe is from the cutless bearing resonating thru the shaft and the blade tips cavetating under the hull. This only happens when I start backing up or moving forward. Once in motion the noise stops. The only time I hear this kind of noise on plane is when I'm turning sharp.

I don't think it's that unusual. I've been on larger single screw vessels and heard the same kind of noise.

Keep in mind that bearing generated noises aren't usually intermittent and "if" they are, they won't be for long.

Hope this helps.

Thanks for all the comments. I do appreciate them. It's good to know we all share the same passion.
Thanks again...

Hey guy, feel free to call me tomorrow at 904-716-3804. We can compare noises. I think yours is lke mine.

Mine doesn't make any noise at all - i mean it doesn't run either tho so good and bad