Ericson 30+ Prop, Shaft & Strut

[Dave G.]

I have a couple of questions for in particular for my fellow 30+ folks here but all info will be gladly accepted. After pulling her out for the season I have discovered something that is puzzling. A little backstory..This is my first year with this boat and during the season I had issues with what I thought was an engine alignment or possibly shaft slightly tweaked as I had a vibration I could not get rid of. With the boat on the hard I now have a good view of all the possible perps. I have a 13" 2 blade fixed prop that is 2.25" from the strut & the clearance between the hull and the prop is only 1". Both of these measurements seem to go against operational norms and I'm guessing the lack of prop clearance is the primary contributing factor to my vibration issues. Funny thing is I've been spec'd a 15" replacement prop by a couple different companies and that is obviously never going to work with my current geometry. It seems I need to extend the shaft with the current 13" prop a couple of inches just to get enough hull clearance. Of course that would extend the shaft length aft of the strut to 4" which is going the wrong direction yes/no ? The other option is to go to a 12" prop which is not real appealing at all. Curious if other 30+ owners know and can share how their boat is set up.

 

[Frank Langer]

I have a couple of questions for in particular for my fellow 30+ folks here but all info will be gladly accepted. After pulling her out for the season I have discovered something that is puzzling. A little backstory..This is my first year with this boat and during the season I had issues with what I thought was an engine alignment or possibly shaft slightly tweaked as I had a vibration I could not get rid of. With the boat on the hard I now have a good view of all the possible perps. I have a 13" 2 blade fixed prop that is 2.25" from the strut & the clearance between the hull and the prop is only 1". Both of these measurements seem to go against operational norms and I'm guessing the lack of prop clearance is the primary contributing factor to my vibration issues. Funny thing is I've been spec'd a 15" replacement prop by a couple different companies and that is obviously never going to work with my current geometry. It seems I need to extend the shaft with the current 13" prop a couple of inches just to get enough hull clearance. Of course that would extend the shaft length aft of the strut to 4" which is going the wrong direction yes/no ? The other option is to go to a 12" prop which is not real appealing at all. Curious if other 30+ owners know and can share how their boat is set up.

Hi,
We have a1984 E30+ and have faced the same issues. We have a Varifold 2 blade folding propeller (which I really like). It's a 13 x 9, which is all I can fit. They recommended a 15 x 9, but that will hit the rudder. Although I may be slightly under propped, I can motor at 6 knots, 2240 rpm which I think is ok.
I do have some vibration from the engine, but have minimized that through careful engine alignment. I usually achieve 002, which helps alot.
I have the 2 cylinder 16 hp, model 5416 engine, with three motor mounts. It just vibrates. Some others on this site have converted to four motor mounts which I'm sure helps reduce vibration, but it's alot of work.
I think it's a matter of making the changes you can, without going overboard, and living with a bit of vibration.
Frank

 

[bigd14]

Hi Dave- I had major vibrations when I got the boat. The first thing I did (after replacing the corroded strut, but that is probably a different issue) was to replace the motor mounts, and went from three to four mounts. This cured probably 2/3rds of the worst vibration. The other thing I did after a couple years was replace the old 13 inch Campbell Sailor 3 blade prop with a 12 inch 3 blade Campbell Sailor. This improved max rpm (2500) and efficiency (5.7 knots at 2200 rpm) and surprisingly added another 1/3 improvement in vibration. I could probably have it re-pitched and get a few more rpm but it seems OK for now. So next up is to try to get the engine in finer alignment and see if I can get further improvements.

The way I understand is that the shaft should only extend one shaft diameter past the strut to the front end of the prop hub, so you are a little over, but much better than I am (prop hub sits about 4 inches back). Is the shaft straight?

Check your motor mounts by grabbing the engine (with it off) and seeing how much you can wiggle it back and forth. It shouldn't move very much. If you do get movement, I would start with replacing the mounts. Then check alignment. Does the prop spin freely now? Make sure the bolts holding the mounts down are secure. The lag bolts have a tendency to loosen up. Finally, if no major improvements, then you could consider a different prop.

Good luck with it.

Doug

 

[Dave G.]

Hi,
We have a1984 E30+ and have faced the same issues. We have a Varifold 2 blade folding propeller (which I really like). It's a 13 x 9, which is all I can fit. They recommended a 15 x 9, but that will hit the rudder. Although I may be slightly under propped, I can motor at 6 knots, 2240 rpm which I think is ok.
I do have some vibration from the engine, but have minimized that through careful engine alignment. I usually achieve 002, which helps alot.
I have the 2 cylinder 16 hp, model 5416 engine, with three motor mounts. It just vibrates. Some others on this site have converted to four motor mounts which I'm sure helps reduce vibration, but it's alot of work.
I think it's a matter of making the changes you can, without going overboard, and living with a bit of vibration.
Frank

Thanks Frank, Do you know what the distance is between your strut and prop ? I'm thinking I either need to get a longer shaft or smaller prop. I think that the hull clearance is the more problematic vs a little longer shaft. BigD has 4" between prop and strut so if yours is about the same as his that would answer why I have the hull clearance problem. If I add 2" to shaft length I think I would have sufficient hull clearance.

 

[Dave G.]

Hi Dave- I had major vibrations when I got the boat. The first thing I did (after replacing the corroded strut, but that is probably a different issue) was to replace the motor mounts, and went from three to four mounts. This cured probably 2/3rds of the worst vibration. The other thing I did after a couple years was replace the old 13 inch Campbell Sailor 3 blade prop with a 12 inch 3 blade Campbell Sailor. This improved max rpm (2500) and efficiency (5.7 knots at 2200 rpm) and surprisingly added another 1/3 improvement in vibration. I could probably have it re-pitched and get a few more rpm but it seems OK for now. So next up is to try to get the engine in finer alignment and see if I can get further improvements.

The way I understand is that the shaft should only extend one shaft diameter past the strut to the front end of the prop hub, so you are a little over, but much better than I am (prop hub sits about 4 inches back). Is the shaft straight?

Check your motor mounts by grabbing the engine (with it off) and seeing how much you can wiggle it back and forth. It shouldn't move very much. If you do get movement, I would start with replacing the mounts. Then check alignment. Does the prop spin freely now? Make sure the bolts holding the mounts down are secure. The lag bolts have a tendency to loosen up. Finally, if no major improvements, then you could consider a different prop.

Good luck with it.

Doug

Thanks Doug, I have been thinking of replacing the front mount with a plate and adding 2 mounts as a single point on a post type mount just doesn't seem like a good design choice. The prop/shaft spins freely and I don't see any "wobble" with the naked eye. I have found a couple of pics of 30+ boats for sale and they both appeared to have more space between the prop and strut than I have. I also asked Frank if he knew what that space was so that may cement one resolution. I have checked the lag bolts and in fact had to repair one of the front mount bolt holes as it was stripped out, another weak point for sure. Do you know the pitch of the those props, the 13" and 12" ?

 

[Kenneth K]

I have a 13" 2 blade fixed prop that is 2.25" from the strut & the clearance between the hull and the prop is only 1". Both of these measurements seem to go against operational norms and I'm guessing the lack of prop clearance is the primary contributing factor to my vibration issues. Funny thing is I've been spec'd a 15" replacement

I doubt that the prop-to-hull clearance would be causing vibration. Intuitively, there needs to be "some" clearance, but I've never seen it published what the recommended minimum clearance should be.

As Big D has already mentioned, the recommended max clearance from prop-to-strut is about one shaft diameter. As you go longer than that, asymmetric prop loading (the same thing that causes prop walk) increases the side loads and wear on both the strut and the cutlass bearing. Also, with greater prop-to-strut distances, vibrations and wear increase greatly from things like nicks, barnacles, or other imbalances on the prop.

Since you can't fix both measurements (short of a smaller prop) my take is that the prop-to-strut distance would be the bigger concern (and the more likely cause of vibrations). Maybe a knowledgeable prop shop could advise you further.

 

[Frank Langer]

I doubt that the prop-to-hull clearance would be causing vibration. Intuitively, there needs to be "some" clearance, but I've never seen it published what the recommended minimum clearance should be.

As Big D has already mentioned, the recommended max clearance from prop-to-strut is about one shaft diameter. As you go longer than that, asymmetric prop loading (the same thing that causes prop walk) increases the side loads and wear on both the strut and the cutlass bearing. Also, with greater prop-to-strut distances, vibrations and wear increase greatly from things like nicks, barnacles, or other imbalances on the prop.

Since you can't fix both measurements (short of a smaller prop) my take is that the prop-to-strut distance would be the bigger concern (and the more likely cause of vibrations). Maybe a knowledgeable prop shop could advise you further.

Dave,
Looking at it from the dock, without getting into the water with a tape measure, the distance between strut and prop is at least 3 and maybe 4 inches. I would prefer to have it less, but I probably need that for my 13 x 9 inch prop.
Frank

 

[bigd14]

The old prop was a 13-7 and the new one is a 12-7. Since I cannot get full RPM's I could see going slightly lower in pitch. But I think its not worth the trouble right now. Maybe if I have a longer haulout sometime I will send it in to repitch.