prop not clearing anode

[boatman37]

So replaced my anodes and bought a new prop. Book says it came with a 16x16 but it had a 14.5x17 and I was only hitting 3800 RPM. Bought a 15.75x15 but slipped it on and the prop hits the 'fin' anode. I read somewhere that the power steering optioned boat doesn't need that 'fin' on that anode but instead can use a 'puck' style? Can I just trim my new anode (magnesium)?

boat is a 1986 sundancer 250 with alpha 1 gen 1

 

[Grub54891]

Yup, you can trim the anode, When I ordered a new prop, they sent the wrong one and told me to trim it. I refused, made them send the correct one. I've seen others that had been trimmed also. I just did not want to, as it was their mistake.

 

[Scott Danforth]

2 minutes with a file is all you need

 

[boatman37]

Figured as much. Wife told me to order a different anode. Told her I will save the $15 and be good as new...lol

 

[Davetowz]

I "fixed" my clearance issue with a grinder. On the anode, not the prop.

 

[boatman37]

So how much clearance should I have between the prop and cavitation plate? I took the anode off and spun the new prop and it's about 1/4" from the cavitation plate at the closest point. The boat calls for 16x16 from the factory. This one is a 15.75x15. It's a Solas Amita 3 E Plus 1511-158-15.
I figure 1/4" is enough clearance but want to be sure.

 

[jimmbo]

A 1/4" is more than plenty
How much clearance do you have with the Trim Tab?

 

[boatman37]

A 1/4" is more than plenty
How much clearance do you have with the Trim Tab?

The anode? Plenty right now. I took it off...lol. Still have to grind it for clearance. I will be sure to have at least 1/4" clearance on the anode too.

 

[QBhoy]

Very unusual for a boat to come new with a 16x16. These are normally an after thought and quite effective on boats like yours...for get up and go, not so much efficiency and top end.
It likely came with a normal prop like a 14x17 or similar.
Just a thought.

 

[boatman37]

Very unusual for a boat to come new with a 16x16. These are normally an after thought and quite effective on boats like yours...for get up and go, not so much efficiency and top end.
It likely came with a normal prop like a 14x17 or similar.
Just a thought.

I have the original paperwork that came with the boat (bought from the original owner) and pretty sure I remember seeing in there that it came with a 16x16 or that was what it was supposed to have or something. Anyway, had a 14.5x17 and was about 400 RPM light on max RPM. Top speed was supposed to be 32 but I was hitting about 34 so figured a 2 pitch drop should be pretty close. I hope the efficiency isn't hit too hard.

 

[QBhoy]

Hi Boatman

Those 16x16 seem to work really well on such boats. I have a friend with a 28ft bayliner and 5.7. After 10 years of it not performing that well with some people and weight on it...the local Merc dealer suggested the prop change to a 16x16 (from the original 17” black max....what a difference in it. Wasn’t as quick too end, but made it plane so quickly and cruised on the plane much easier at lower revs. Think he said he found it was better at manouvering at slow speeds too.
In your case, it’s likely the broker or dealer spec d the prop afterwards maybe ?

 

[boatman37]

not sure. i bought it from the original owner. he had 3 props, 2 were aluminum 14.5x17's and one was a SS with similar specs. i ruined the first aluminum prop at first launch after we bought it. put the other aluminum one on it but never tried the SS one. a dock neighbor bought a new SEI drive for his and needed a new prop so i let him borrow the SS one. he liked it so i sold it to him so now down to just the one prop. hopefully the new one works good. i used to be able to stay on plane at about 24 MPH and i think about 3000 RPM but can't remember now. I do know when i first bought it we had 7 of us on there and couldn't get on plane but that was also right after i banged up the prop and also understand 7 is a big load and probably shouldn't expect to get on plane with 7 anyway...lol. 95% of the time it is just me and my wife on the boat and no problems getting on plane with the old prop, even with full fuel, water, and coolers.

EDIT: oops...got on a tangent there. Anyway, the original owner said that was the same prop that came on it (same specs) but that was also 30 years ago and who knows if he actually remembered what it was

 

[boatman37]

Got the anode trimmed. How much clearance is needed? I have about 1/8" on top and 1/8" towards the rear (where the prop would push water towards). The anode hangs down behind the prop. I would think if the prop flexes it would flex towards the front of the boat which would give me even more clearance? I can trim a little more if needed but it fits as is.

 

[boatman37]

Another question...the old anodes i took off were quite a bit heavier than the magnesium ones i bought. would they be zinc? doubt they are aluminum and be that heavy? for freshwater can i use zinc? or aluminum? or do they have to be magnesium? boating on the ohio river near Pittsburgh if it matters

 

[dingbat]

Are you sure you have the right prop spacer installed?

Never heard of shaving anodes to make room for prop. I’ve had to change a couple of spacers during prop swaps.

magnesium is first choice for freshwater. Aluminum is acceptable. Zinc is not recommended

 

[boatman37]

unsure on spacer. i just left the old one on. didn't realize there were different size spacers? i guess a thinner spacer would move it closer to the housing and add more clearance for the anode but won't change the distance to the cavitation plate (which is about 1/4")

 

[boatman37]

Got the new flat anode from boatzincs today. fit perfectly and have 1/4" clearance now. boat has power steering so don't need the fin

 

[boatman37]

Well everything seems to be working great. Prop clears the new anode and it's like a new boat now. The other day I noticed a bend in the one fin on the old prop. Took the boat out yesterday with the new prop and it feels so much smoother, pops up on plane much easier and my top speed was 37.5 MPH at 4600 RPM. The old prop only netted 34.5 MPH at 3800 RPM so must have been worse than I thought.

 

[Bondo]

so must have been worse than I thought.

Ayuh,..... That's very, Very common with props,.....