Couple of items to check:
1) When you installed the new motor was the coupling in the same horizontal position relative to the boat? In other words did you move the shaft in or out at all to match it up with the motor shaft? On mine I had to pull the shaft inboard about 4 inches. In doing so, this moved the outer diameter of the prop to within 1.5" of the hull. It really should have been 2+". In your case it should be 2.25 or more inches but check that as I'm no expert (distance should be 17% of prop diameter). Having it too close can start to cause vibration and/or cavitation as RPM's go up.
2) No more than 40x the shaft diameter should be without the support of a strut. This will cause vibration as RPM's go up. Also check your cutlass bearing. There should be no play when you move the shaft side to side for a new one. Too much play in a worn cutlass bearing would cause what you are describing and finally, make sure you have aligned the prop shaft to the motor shaft precisely. Any combination of the above can amplify problems. These things may not be the problem since you did not experience these issues with the old engine but worth a check since you can now notice this sort of stuff more acutely simply because the engine noise and vibration is not blocking it as you mentioned.
Wayne
Sequoia T30.
--
Sent from my Android phone with K-9 Mail. Please excuse my brevity.
I installed a new electric engine (Electric Yacht 180ibl) in my CAL 2-29
this year. After many issues, due to my lack of experience on changing
out an engine, rather than the engine itself, I have it running
beautifully and praise its virtues to everyone I can.
The one remaining thorn in my side is my prop. It's cavitating. I have a
MaxProp 13" 2-blade. I explained the problem I was having to Scott. I
realize it wasn't his area. But since the prop was the one that came off
the boat, and I had it set to what it was before, and it was the
dimensions I'd given him when I ordered the engine, I hoped he might
have a suggestion. He suggested that I decrease the pitch and see what
happened.
Well, it was cavitating at about 850 RPM and vibrating at 1000. After
decreasing the pitch to 10", the vibration was down to what I'd expect a
moving boat to do. But the cavitation still happened at about 1250 RPM.
I contacted MaxProp's distributer, who told me the 'proper' settings
were 13X12, my original settings. When I told him that that's where it
was when I had the problems, he told me I'd have to 'experiment'.
My marina is willing to leave the boat on the sling so I can adjust the
prop. But that still costs me $$ and time. Besides, it's pretty
irritating to be this close and still have problems.
So I was hoping someone here might have had a similar situation and can
offer a solution.
The prop is the one that was on the boat before, with a Westebeke 18W.
Those are the settings that worked. Well, I think they worked. Frankly,
I know alot more now than I did then and can't swear to as much.
Besides, the electric engine is much more quiet, so it's easier to be
much more sensitive to issues.
Anne Racel
4 Degrees
http://boatjournal.stuffandjunk.net
No comments:
Post a Comment