Vibration Issue

The vibration I had was pretty chronic. It would shudder and shake the boat as soon as the engine was put into forward gear. But if you could ride it out, after around 10-15 seconds it would smooth out to only a fraction of what it was before, as by then, the prop had opened fully.

I should mention the folding prop was NOT geared - so the blades opened and closed independently of each other.

The vibration had been there for years according to the PO, who had been conditioned to accept it.

It was too violent for me to put up with, and I figured it would eventually cause more serious problems (engine mounts, strut, cutlass bearing, etc), so I had to address it.

Our 35 yr old prop was clean, and nothing there caused it not to open correctly. The prop did have a couple of dings on the blades, but unlikely to be the cause of the problem. In talking to Gary over at Martec, he told me about the stops, etc and that they could most likely refurbish it. So I sent the prop off to sunny California for a makeover.

When he tested the prop, Gary said it had excessive electrolysis within - which is not visible on the surface, and the prop looked in good condition on the outside. This electrolysis meant the welds to repair the stops, etc, would not "stick". Thus, it was advisable to replace the prop.

I was adamant that I wanted a 2 blade folding prop, as we mostly sail, and can do quite long trips, and I did not like the thought of dragging a fixed blade prop under the boat. We chose Martec as they seemed to have a very good reputation, and are respected by their peers.

So we picked the Martec Mark III Eliptical 2-blade folding prop (not geared).
It is an 11" blade, and I would think the A-4 could handle bigger blades (just my opinion, I'm no expert), but we do not have clearance for anything larger.



We are delighted with the prop. It has great torque in forward, very good cruising speed at lower rpm's, goes in reverse acceptably, and most important to us; it opens and closes perfectly every time!!

I don't remember exactly, but we put down something like $600 on the prop (whereas a fixed prop would only be half that price), so it was not inexpensive, but it was worth it to us.