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S/S prop noise?

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kdhskiff

Member
Once again I am seeking the input from the pros on this forum...Finally got my new boat in the water (winter sucks) with a new BF150...Ordered new with an S/S prop. Definitely not the quiet Honda sound I'm used to, its noisy down low, especially in reverse. Local Marine shop says S/S prop is the culprit. Anyone ever heard of this? Best described as a combination of exhaust leak, and light rhythmic tapping, along with slight vibration...seems to clear up with speed/RPM, although (when going forward) I need to trim down pretty far to get it to quiet down. Checked all the obvious stuff. It could stand to be lowered on the transom a notch (which I will do). This is my second Honda outboard, my BF90 (also a new purchase) had an aluminum prop & it was whisper quiet... any ideas appreciated, Thx folks!
 
On a hose or in the water ?----Height of the transom ?----Motor model #----Sometimes a stainless prop can cause bouncing / rattle in gear at idle speed.
 
It's about 1 to 2 inches high, I have one adjustment hole left that should get it closer. I was going to ask that very question... FYI my boat is a Carolina Skiff 218 DLV.
 
johnnygjr said:
It should be level,never above,1/2 inch below is acceptable
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Thanks, not sure if it will make it to the level mark, but it should get close...the noise I'm hearing tends to go away when the motor is trimmed down all the way. If I trim up to find the sweet spot for speed, the boat speed increases, but engine (and the noise I described) gets louder. This is what made me think the dealer mounted the engine too high. Cruising with the engine fully trimmed down seems odd to me...hope lowering it helps. I'll report back after I lower it.
 
That prop should NOT be making any noise that you could detect. Pull prop and check it thoroughly. Make sure the castle nut has been tightened properly. Make sure the thrust washer is tight against the prop. Make sure the prop is tight on the splines. Run the engine with the prop off and see if there is still noise. If so, then you have a problem with the lower end. If you are lucky, the shift rod will just be out of adjustment.
 
Done all of that except operate engine with prop removed. I will do that this weekend. Its basically a loud engine...not like the quiet Honda purr I'm used to. It quiets down with acceleration/speed AND a full trim down. I believe some of the noise is exhaust, although the lower unit is fully in the water. I do believe the engine was mounted too high on the transom (by the dealer), and I will lower it this weekend. The ventilation plate is about 1.5 inches above the bottom of the boat, and I'm told it should be level. After that I'll re-evaluate and switch to an aluminum prop just for grins (need a spare anyway). I want to rule out all possibilities before taking it back to the dealer...I just cant believe there is an issue with a brand new motor! Thanks
 
Also, my boat (218 Carolina Skiff DLV) has a lower transom "pocket", so should the ventilation plate be even with the top of the pocket or the actual bottom of the boat?
Thanks to all for your valued input on this!
 
Not sure what you mean by a "lower transom pocket." Can you post a picture?

Here is what you ultimately want - when the boat is on plane, the anti-cavitation plate (it's actually an anti-ventilation plate) should just be skimming the top of the water coming off the transom - not digging into the water at all.
 
This is not my boat but a pic of the "pocket" (not sure if that's the right term)....anyway, I'm guessing that the ventilation plate should be inline with the actual bottom of the keel and NOT the top edge of the pocket...Correct?

IMG_0194.jpg
 
Use a poor mans stethoscope just hold your ear on the handle of a long screwdriver and see if you can isolate the noise. Be carefull of moving parts especially if in gear. Touch different points of the gearbox the closer you are the louder the noise.
 
At my age, the old screw driver trick doesn't work as well as it did when my hearing was better. If you are near an auto parts store, most carry a mechanic's stethoscope for around $10.00. Most of those have long probes to make the job easier.
 
Thanks all.... for the record, I’ve been a professional auto tech for 41 years, and have been with Honda exclusively for 27. As such, I have a great appreciation for the knowledge and experience of others. Even though many diagnostic and repair procedures are similar, there are areas that are specific to the marine world. That’s why I joined this forum! Once I get this issue sorted, I will post my findings. Thanks again!
 
Been a while, so thought I would follow up...I replaced the S/S prop with a 4-blade Honda aluminum unit (correct pitch & diameter) and an absolute night & day difference...nice and quiet! Guess my engine does not like S/S props. Note the S/S prop weighed 12 lbs, the Honda aluminum prop half that at 6 lbs. I'm curious if any other forum member has ever experienced a noise using an S/S prop?
 
As per post # 2 a stainless prop can bounce on the clutch dog.-----An ultra high speed camera might see that at idle.-----Power flow from an engine comes in pulses as each cylinder fires.
 
racerone said:
As per post # 2 a stainless prop can bounce on the clutch dog.-----An ultra high speed camera might see that at idle.-----Power flow from an engine comes in pulses as each cylinder fires.
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Exactly...but the phenomenon you describe should be more noticeable on a hose as opposed to being submerged, when the surrounding water dampens the pulses. In my case, you could hear the noise while in the water - very unnerving when one is used to the quiet purr of a Honda outboard motor. It's nice and quiet now with the lighter aluminum prop.
 
I don't have any experience at all with the 90 hp Honda, but that just sounds weird to me. I've had both aluminum and SS props on several boats I have owned - admittedly all with bigger engines - but have never heard any noticeable differences in noise level coming from the prop. Could be that my hearing is not as sharp as it once was.

BTW - did you lower the engine at the same time and test both props?
 
chawk_man said:
I don't have any experience at all with the 90 hp Honda, but that just sounds weird to me. I've had both aluminum and SS props on several boats I have owned - admittedly all with bigger engines - but have never heard any noticeable differences in noise level coming from the prop. Could be that my hearing is not as sharp as it once was.

BTW - did you lower the engine at the same time and test both props?
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It’s a 150 BTW...No, I have not lowered it yet, I wanted to try the prop swap first. Hey chawk, I see you’re in Hague, just there this past weekend...it’s where I do most of my striper fishing! Small world...👍
 
You've got to wonder if the SS prop was fitted correctly (i.e. right hub, ect.) - maybe it wasn't and the other prop has been fitted correctly.

I'd be swapping them back just to see if the noise returns!
 
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