I think I have too much prop

StanKromfols

StanKromfols

Member
Mar 18, 2023
36
Northern California
Boat Info
2002 Sea Ray 17'6" Bow Rider Alpha one
Engines
3.0 Alpha one
I recently purchased a 2002 Sea Ray 176 Bow Rider with the 3.0. The boat will be used mainly for pleasure cruising with just my wife and I. It's been quite a while since I've owned a boat, so I'm trying to reeducate myself as I go and appreciate all of the information that's been provided by members of this forum.

My latest question is prop size, I have a Quicksilver QA1918X 21P prop on the boat. I'm not sure about the 1918, but the 21 I've got to assume is the pitch, and that seems like quite a bit for this boat. Can anyone tell me if my thinking is correct ? The Tach is way off and I'll be looking at that (at idle it registers 2,000 RPM and the engine is nowhere near that), and the speedometer seems to be way off too, and I'll also be checking that out. I've found vid clips on Youtube with suggestions for addressing both the tach and the speedometer, but haven't found anything about prop sizing.

Does anyone have experience with this size boat and engine and have suggestions for prop size ?
 
Go to sea rays website under owners and there is a prop chart to use a basic starting point. You boat shows a 14 1/2 dia and 21 pitch if I read it correctly.
 
What are you basing the thought of "too much" prop on? The correct prop will get the engine to at/near/slightly above max RPM (which is 4,800 for your engine, if memory serves). This is typically measures with a light load in the boat and going WOT and trimmed up as high as you go before ventilation.

So... get the tach sorted then test.

But... 21" sounds about right... again, from memory. Probably somewhere between 14" and 14-1/2" diameter. That you can easily measure. Sea Ray's website has a prop matrix - double check me on those numbers.

Clear the pitot hole on the leading edge of the drive. Remove the quick connect clip above the anti-vent plate and check for air flow.
 
Dennis, I didn't really know what to expect in the way of a hole shot or what it should take to stay on plane, but it just felt sluggish, like it was over propped, but that may also be because the engine isn't tuned as well as it should be. I'm trying to find a good mechanic to give the engine a good look. The older gentleman I bought the bought from was selling it for his daughter and couldn't tell me what it was last serviced, and although the engine and engine bay look great the engine could still need tuning.The weather is starting to cooperate so I can start addressing these bothersome little problems.

Scoflaw, I don't have a timing light and am not mechanically inclined, so I'll just have to wait until I find a good boat mechanic.

Boatrboy, thanks for that information. It told me that my prop should be a 14 1/4 with a 21 pitch, which is what I have. So I'll look at engine tune and engine tilt.
 
Don’t mess with changing props until the engine is in proper order.

Old fuel and filter, worn plugs, corroded distributor cap etc……..none of these can be fixed with a prop replacement.
 
I had a 1984 3.0 on a 19' boat. This was the 140 HP version. Yours is either a 130 or 135.

I ran a Michigan SS 21P prop that was repitched to 20". It literally jumped out of the hole. I could run 8 people in the boat (4 adults and 4 kids) and it would still plane like a champ.

Mine had points for a few years. Then I replaced them with a Pertronics Electronic Ignition setup and that made the engine run much better. It's likely yours is electronic, but if not an upgrade would be worthwhile.
 
Thanks for the info Jim. I've got a lot to learn about this boat. As I mentioned above I need to have a good boat mechanic check the engine tune and I need to address the Tach and Speedo problem. Just a lot of little stuff to make things right.
 
Side note on HP... the older engines were rated at the crank while the newer ones were rated at the prop. An 80's 3.0 was (apples to apples) more like 115HP or 120HP.

Stan, I've run A LOT of boats like yours. With the pitch being the same as an aluminum prop, there's no real benefit because the SS prop is so much heavier and it takes more power just to turn it. This comes from extensive testing with many different props, a stopwatch and a GPS.

Now, that is with Mercury props - which typically use beefier SS than some aftermarket ones. So there's some other variables at play there. But, generally, all things being equal... the price vs performance of a SS is not worth it. For example, a 19" 4-blade Al will beat out a 19" 3-blade SS in hole shot and 0-30MPH.
 
I found a mechanic with great reviews. He thinks he can take a look at my boat in about a week. I asked him to check everything over, change fluids and let me know if anything else needs adjustment or repair. I just want to start with a good running engine that I have full confidence in. Then I can start looking at minor changes or adjustments.

And Dennis, I agree with you completely. I see no need for a Stainless prop. I'm not going to be worrying about top speed, and probably won't be pulling any skiers or tubers, so don't need a super hole shot. Just comfortable cruising on the delta.
 
A good "checkup" is always a good idea every so often

StanKromfols said:
And Dennis, I agree with you completely. I see no need for a Stainless prop. I'm not going to be worrying about top speed, and probably won't be pulling any skiers or tubers, so don't need a super hole shot. Just comfortable cruising on the delta.
Click to expand...

SS won't really be better or worse - it's pretty much the same. It's that the extra cost of a SS doesn't really have a "ROI". With bigger engines, it does - there just isn't enough torque with the 3.0L (which is still a GREAT engine).
 
Lazy Daze said:
A good "checkup" is always a good idea every so often



SS won't really be better or worse - it's pretty much the same. It's that the extra cost of a SS doesn't really have a "ROI". With bigger engines, it does - there just isn't enough torque with the 3.0L (which is still a GREAT engine).
Click to expand...
I bought my first SS prop back in about 1977. My motivation was to minimize repairs since every weekend we anchor on a sandbar. It certainly accomplished that objective. The mechanic at the marina said that SS was so heavy that it would hurt the motor. That may have been true in the old days, but I would disagree now.

Mercury has some awesome SS designs that impact greatly on performance. My last change was from a black Max to an Enertia. Hole shot, fuel economy, bow rise, prop slip, etc etc were all better. At $600 is probably was not cost effective, but it makes me smile every time I hit the throttle.

BTW, many of my prop optimizations have been with a 3.0. The caveat is that whatever prop you use, you must adjust the pitch so that the WOT rpm meets the max spec. Much less than that and the prop will be perceived to be substandard.
 
StanKromfols said:
I found a mechanic with great reviews. He thinks he can take a look at my boat in about a week. I asked him to check everything over, change fluids and let me know if anything else needs adjustment or repair. I just want to start with a good running engine that I have full confidence in. Then I can start looking at minor changes or adjustments.

And Dennis, I agree with you completely. I see no need for a Stainless prop. I'm not going to be worrying about top speed, and probably won't be pulling any skiers or tubers, so don't need a super hole shot. Just comfortable cruising on the delta.
Click to expand...
This is a good plan. Get the engine maintained and get the tach fixed before you play with props.
See where your wot rpm lands and adjust from there.
I suspect depending you may be ok if its just the two of you. If you want to tow a skiier or tube you may want to drop down in pitch.

i had a1990 sea ray 170 with a 3.0, i ran a 4 blade 18” for cruising and tubing, swapped on a 16” 4 blade for skiing.this was withseveral people in the boat, and im a big guy so really helped the 3.0 get by…

miss that boat, id put $65 of gas in a go all weekend and still have a 1/4 tank left
 
Jim and Scott, thanks both for your information. It's always good to hear from those with vase experience and consider what they've discovered.

Back in the 80's when I did a lot of boating (mostly waterskiing) I found an old Johnson 75 hp. The big old 4 cylinder engine. It had thrown a rod so I got it for almost nothing. I found a boat mechanic who'd been rebuilding these engines for years (Huitt Chalk) and he completely rebuilt the engine. He promised me it would be a beast, and it was. I put it on a new 16 ft open bow tri hull and with 4 adults in the boat it would pull my wife and I both out of the water on single skiis at the same time. And if memory serves me, I had an adjustable pitch prop that I change in just minutes. It really hurt when I had to sell the boat, but it went to a good friend, and I went to Guantanamo Bay, where I built a pontoon boat, but that's another story.
 
I think this is a good plan, get the motor running correctly then look at the prop. I found with my 185 (4.3 V6) that I was in between props, a 21P would bump the rev limit at 4950rpm and a 23P would barely get me to 4600rpms, although at a higher top speed. I switched them around some, but mainly ran the 21P. I stuck with aluminum, just did not see an advantage for SS on that boat. So what is my point? Stick with aluminum and buy one or two different props (for the price of 1 SS), to dial things in, you will also have a spare -- be sure to buy a second hub kit also.
 
So there a couple of way(s) to tell if you have too much pitch in a prop. The best way is to at moderate loading make sure you get max RPM out of the engine. If you don't there are a few things to try. Change pitch or diameter. Diameter would only be change if you didn't get on plan quickly if max rpm is achieved.

Those are the basic's as this is a much discussed topic and there are website(s) that have been dedicated to this topic. Get your tach working right first, then worry about the prop.
 
Stan I hope you have this all worked out by now but thought I would inject a thought for you.

I recently purchased a 99 180BR with the 135 HP 3.0. My tach and speedo appear to be very accurate.

One thing I noticed that is critical for getting on plane is to have the trim ALL the way down when you take off. The least bit of upwards trim makes my boat plow forward with the nose up. Trimmed all the way down it will plane in 3 seconds with two adults and some gear. It takes 20 or 30 seconds to get on plane with 2 children in the rear and 4 adults in the forward seats.

My 180 parts manual calls for a 14x23 prop. It has a SS prop on it that I think is smaller than that. I was also given a aluminum prop that is 14.25x21.

The previous owner said he had all the rubber boots and hoses replaced when he got it some years back including the speedometer tube. My speedo is dead on accurate with the GPS. Haven't checked the tach but it seems to be correct just judging by engine sound and boat performance. I trim out at 43.5 MPH per the GPS at 4400 RPMs per the tach with two adults and some gear.

Your speedometer may need a new tube. I can't imagine how much trouble it is to install though. If mine weren't already good I would just rely on the GPS.

Good luck and happy boating!
 
Sorry that it's taken me a while to get back on the forum, but I've been traveling and didn't have time to spend on my computer. I appreciate what each of you suggested. Now that the weather is looking good in Northern CA I'll try to get the boat out again and do some experimenting. The speedometer seems to be working properly now, but I'll have to spend some time working with the tach. Once that's right I'll be able to see just what the RPM will max out at, which should tell me if I have the correct pitch.
 
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