Prop Recommendation

[YEM]

Hello

My issue has two parts: (1) A shuddering at very low speed, but not in neutral (2) boat is running low and slow at normal rpm. My prop does have some minor visible dings on the leading edges. Is it plausible that all of the symptoms could be prop related? Most folks seem to run with a different prop than the one I have (14x23 / 3 blade).

THE DETAILS:
The past couple of times that I have brought the boat out I have noticed a slight shuddering feeling when traveling at no wake speed (almost like grass stuck on the prop - but it is clean). It does not seem to change when I turn left right or change the engine tilt. This shuddering is not noticeable when in NEUTRAL.

When I throttle up it is not noticeable and the boat feels smooth. However, I feel like the boat has added drag. By this, I feel like we are not riding as high on plane and we are running 5 to 10 mph more slowly. This is particularly true when I am the driver and the wife and kids are in the bow (which NEVER used to be a problem). If everyone is sitting in the cockpit, the boat rides higher and faster.

My speedo is not usually reliable (keeps getting clogged), so that is not a good indicator. RPM's look okay (I normally cruise at 3200 to 3500 rpm). In this RPM range I've noticed a lot of side spray from the bow area, and I feel slow. Typically on flat water I am getting side spray from just behind the helm.

No other noises, smells, or vibrations coming from the engine or lower unit. Last winter (1.5 years ago) I had the gimbal bearing replaced when I had the exhaust and shift cable bellows done. I have not observed any in-leakage into the bilge.

Any Recommendations?

1. Year, make and model of boat
1999 Sea Ray 180BR

2. Length, width and base weight of boat, look for boat decal on back of boat
18 ft length, 7.5 ft beam, 2100 pounds

3. Number of people and gallons of gas normally on boat
2 adults & 2 kids / 10 - 20 gallons of fuel.

4. What do you use the boat for
Tubing and cruising on the Connecticut River, and occasionally water skiing in lakes

5. Is it a Deep Vee and if so how many degrees of deadrise
Deep Vee 19 degrees

6. Year, make and model of motor
1999 Mercruiser Alpha One 3.0L (original stock)

7. HP and gear ratio of motor
135HP / 2.00x1 GR

8. Manufacturer’s recommended WOT range
4800 rpm WOT

9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
n/a

10. Does it have a hydrafoil or trim tabs
NONE

11. Make, model, diameter, pitch and whether SS or aluminum prop
Mercury Quicksilver Alum. 14x23 / 3 blade (48-832834 C1-23)

 

[Sea Rider]

Re: Prop Recommendation

If boat feels slow and with excessive w?ter drag could be due to having a spun hub, inappropriate spark plugs, prop pitch or hull flooded with excessive w?ter inside., check. Must perform a wot test with current prop and loaded as usual to check max rpm achieved at wot and see if inside safe working rpm parameters factory stated for that engine. Will know for sure if in need to go for a +,- pitch, independently if cruising at medium throttle.

Happy Boating

 

[steelespike]

Re: Prop Recommendation

23" pitch is right about the max for that setup it must be a struggle to get up on a skis.
Perhaps there is some sort of growth on the bottom, outdrive or prop.
Maybe the trim is not going up all the way or something got changed when they worked on the boat.
You could use a gps for your speed.
Your wot rpm and gps speed would help.Some cells have a gps.
Observe the boat at rest does it seem lower in the water than usual?
Check that the throttle opens all the way.
I wonder if the shift cable or bellows may be against something?
Perhaps the exhaust bellows is pinched stretched twisted wrong one.

 

[YEM]

Re: Prop Recommendation

Thanks for the help Sea Riser and steelespike -

Steelespike, you are right about difficulty skiing on that prop. Kids are not much of an issue, but pulling a grown man is a little trickier. If you are skilled you can get up, but the boat has a hard time getting out of the hole. All the passengers need to ride in the bow. If you are a newbie you will have a lot of crash and burns.

Anyway, here is the info from running this afternoon.

I was the only rider, but had a full tank of fuel (22 gal).
The boat seemed to ride a little better than it has been, but not normal.
The vibration still existed when in drive at no-wake speed; but not in neutral or at planing speed (could this be a damaged prop).

WOT 28 mph @ 4100 rpm (I could not get up to 4800 rpm)
Normal cruise: 24 mph @ 3500 rpm

There were a few times I was cruising along straight, and the it sounded like the prop was getting vented. I put the trim down and no change until I slowed down... Then all was normal. I suspected that the hub was spinning.

My hand-held GPS did not have speed indication, but the speedo was working.
The boat was sitting normally in the water.
There was no leakage via bellows (absolutely dry plug after being out on the water for 2 hours).
Before going out I lubricated all the cables (shift and throttle), and observed full range of motion.
I inspected the bottom paint, and noted no growth...
The paint on the front of the keel is getting sanded down due to beaching, but not flaking or blistering.

I painted a line across the prop and hub. When I pulled the boat out I noted about a 5 degree difference from where they started. My guess is I have a spun hub.

I will be getting a new hub. I also think I will be looking for a new prop since I have that vibe issue (unless you guys feel it is not related).

If I go for a new prop, do you think I should stick with the same setup (14x23 3 blade); or should I go with another recommendation from Sea Ray (14.25x21 3 blade)? What are your thoughts of 4 blades for my setup?

I think it's interesting that I don't get up to 4800 rpm. I've never really paid attention to that before. Does that mean I should go down in pitch?

Any and all recommendations or feed back are appreciated...Thanks for the help!

 

[Sea Rider]

Re: Prop Recommendation

The ideal thing to do is to go for a wot spin with standard prop Factory delivered when new or with a used one assuming it's working in opt state and check it's max achieved rpm. That way will know if under or over proped for your boating aplication. In your particular case won't know how many rpm engine is losing due to having already a spun hub. If you knew previous max rpm when prop was new or working optimum probably will need only 1 or max 2 less pitch to achieve full 4800 if that's the max rpm at wot for that engine.

Happy Boating