I've had my boat for over a year now, and we've seemed to settle into how we use it together as a family. For the most part, its basically used to pull an inner tube with up to 3 kids (roughly 300lbs total), or a single wake boarder of up to 220lbs. Im looking for more bottom end acceleration from what I have now. I looked at the numbers on my existing 3 blade and found this stamped on the hub : 48-832830-c1 . Google tells me this is a 14.5" x 19 prop. The prop guide on Searays website indicates that I should have a 14.25 x 21 prop stock. If my understanding is correct, do I already have a prop set up for better acceleration compared to stock? If so, where do I go from here to get even better low end? A 4 or 5 blade? Any help would be appreciated.
Propeller upgrade.. how to chose?
- Thread starter Joel_CA
- Start date
kaz911
Active Member
The bigger the twist of the prop - the higher top end speed and slower acceleration. (The 2nd part of your numbers are the twist)
As you are already running with less twist than what you have found on SR website you need to start debugging a bit first.
Do a RPM test on your boat - and if you have current and wind - do it twice in opposite directions with / against current if you use GPS as the speed source. Pitot speed source like measured from the stern drive is not really "reliable" unless checked and cleaned often. Make certain hull, sterndrive and props are free of growth and are completely clean.
So write down speed vs RPM (twice) at each of the following RPM's - with 2 people - 1/2 tanks at least and normal equipment. Make certain to trim drive right for each RPM setting on the plane.
RPM's - Speed
600 (idle)
1000
1500
2000
2500
3000
3500
4000
4500
(if possible) 5000
WOT (Wide Open Throttle)
Then when you have done it twice - average the values.
Check your engine manual for what is the right maximum RPM for your engine. You should be close to that. On late 5L engines WOT is around 5000 RPM. But figures between 4600-5100 are within "normal" range.
With those figures it is easier to advise you what to do - and gives you a performance baseline.
How long since you had an engine tune-up done?
As you are already running with less twist than what you have found on SR website you need to start debugging a bit first.
Do a RPM test on your boat - and if you have current and wind - do it twice in opposite directions with / against current if you use GPS as the speed source. Pitot speed source like measured from the stern drive is not really "reliable" unless checked and cleaned often. Make certain hull, sterndrive and props are free of growth and are completely clean.
So write down speed vs RPM (twice) at each of the following RPM's - with 2 people - 1/2 tanks at least and normal equipment. Make certain to trim drive right for each RPM setting on the plane.
RPM's - Speed
600 (idle)
1000
1500
2000
2500
3000
3500
4000
4500
(if possible) 5000
WOT (Wide Open Throttle)
Then when you have done it twice - average the values.
Check your engine manual for what is the right maximum RPM for your engine. You should be close to that. On late 5L engines WOT is around 5000 RPM. But figures between 4600-5100 are within "normal" range.
With those figures it is easier to advise you what to do - and gives you a performance baseline.
How long since you had an engine tune-up done?
Thanks for the reply. I will try and get these figures within the next couple of days. The engine has been recently tuned last fall with all new factory plugs, wires, cap, and rotor. I don't feel any hesitation or misfires from the engine under acceleration from a complete stand still, but sometimes I feel it under acceleration after whipping the tube around under hard turns. It feels completely unresponsive. Ive been reading more and more about this and now i'm starting to wonder if this hesitation is due to cavitation?
J
J
Last edited:
kaz911
Active Member
Can you remember your WOT RPM and Speed?
- Apr 26, 2009
- 5,819
- Boat Info
- '97 330 Sundancer, Raymarine C80 suite with radar, Mercury 310 Hypalon w/8hp Yammie 2stk
- Engines
- 2X 454 carbs w/ vDrives
Cavitation does not feel like hesitation. It sounds more like your prop has come out of the water. The engine revs higher but you don't speed up or the acceleration drops off. If you are feeling a misfire or stumbling it is not the prop. You need to get the engine running perfectly before you start playing around with changing props or you will waste a lot of time finding the right prop. It sounds from your post that you are still having some misfire hesitation in turns. That might mean there is still something needing repair.
When I had a smaller boat I switched from a stock 3 blade to an aluminum 4 blade a very slight bit lower in pitch (1 inch less if I remember) . It was cheap and made a huge difference in hole shot when tubing and staying bit in the water in turns. I could also hold plane at a lower speed, which was good for tubing. I was told that the WOT speed might be lower, but if it was, it was only 1-2 mph max less. I could not tell because where we boat on Georgian Bay big water, small boats are not able to run WOT very much anyway. I think stainless would have been better too, but for the small boat with a 4.3, the aluminum was just fine.
Last edited:
Night swimmer
New Member
Joel most mercruiser engines should run 4800 to 5200 max rpms. If your supposed to have a 21 pitch prop from the factory but now have a 19 than it will help you pull tubes/skiers and heavy loads easier. If you are still looking for a better hole shot than you and don't really care what your top speed it than you can drop down another pitch or 2 or more if you'd like. You just have to remember not to over rev the engine by trying to get to your top speed.
When you talk about it being unresponsive in sharp turns. Do you have the trim up much or is your trim down all the way or close to all the way? If your trim is up to far when the boat leans hard the prop will grab air from the surface and you'll lose acceleration and rpms will rise. That is actually called ventilation.
Cavitation is usually caused by something wrong with the propeller. It's when the pressure on the back side of the propeller drops so low that it boils the water.
Sent from my SCH-R970 using Tapatalk
When you talk about it being unresponsive in sharp turns. Do you have the trim up much or is your trim down all the way or close to all the way? If your trim is up to far when the boat leans hard the prop will grab air from the surface and you'll lose acceleration and rpms will rise. That is actually called ventilation.
Cavitation is usually caused by something wrong with the propeller. It's when the pressure on the back side of the propeller drops so low that it boils the water.
Sent from my SCH-R970 using Tapatalk
Chris Nowell
Active Member
- Nov 28, 2011
- 1,520
- Boat Info
- '05 622 Hardtop w Alaska Bulkhead, 270 Mercury Marine sport inflatable, pulled by a 6.0L Silverado
- Engines
- 4.3 MPI Merc w Alpha I drive, 5 hp 4 stroke Merc aux.
We had the same issue when we were into wakeboarding and solved it with a 17 pitch 3 blade aluminum prop from the dealer. I just had to be careful not to let the engine rev past 4800 rpm when going flat out with that prop. Your boat is probably heavier than the one we had at that time so you may have to take the advice from some of the folks who have tried the high fives and other props designed specifically for hole shots. Our Merc dealer will let us try out the different props before we make a commitment on one specific type, just as long as we don't bring them back with damage. That's a handy service to offer but we lucked out with the first one we tried. Good luck.
This might be the term I'm looking for. It seems to happen when I whip around a hard turn then accelerate (even without pulling anything). I just seem to notice it more when I'm pulling a tube because thats usually the situation I'm in where I would whip the boat around turns and push it hard (usually doing large "figure 8's" in a remote location in the lake). Again, from a stand still to WOT- it pulls like a champ. I never thought to check my trim position. This whole phenomenon might just be user error :smt021.
Guys! Thank you very much for all of your replies. I'm gonna do more testing the next time out to see if it actually is caused by ventilation and this time.. note my trim position.
J
Night swimmer
New Member
Yeah I would definitely check your trim position during both hole shot and fast tight corners. You wanna be trimmed all the way down for best hole shot and for tight corners. For hole shot it'll get you up on plane fastest with minimal bow rise. Cornering it'll hold the most amount of boat in the water giving you a tighter turn with less slide and keep the prop from ventilating.
Sent from my SCH-R970 using Tapatalk
Sent from my SCH-R970 using Tapatalk
torch318
New Member
- Feb 15, 2014
- 36
- Boat Info
- 2007 200 sundeck
perfect pass
factory wakeboard tower
sea dek swim platform pad
- Engines
- mercruiser 5.0 mpi
my 200sd does the same thing when I'm pulling a tube (trim is set at 3 on the smart craft gauge) I did some research last season on the I/O threads on some wakeboarding forums and most guys recommend running a high five prop. My stock prop is a 14.5x17 and it currently has a 14.25x15 three blade on it. I talked to a local dealer and they said that a 19 pitch is as low as mercury goes with a 14.5 diameter high five so I was out of luck but that would probably work for you. Hill marine makes the pleasure five prop in my pitch and they offer free prop exchange if your not happy with the prop you selected you only pay shipping for the exchange. I was talking to another dealer about props and they contacted mercury with my boat specs and mercury recommended a 13.75x19 high five. Not sure why he recommended going down in diameter as that went against everything I had seen about a better holeshot. I was able to demo one and the holeshot with the smaller diameter was horrible but the five blade was awesome in the corners it was a night and day difference. I was planning on ordering a 14.5x15 pleasure five from Hill Marine this season but ended up breaking a piston in my mustang and a forged longblock ate up my budget so it's on hold till next year.
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kaz911
Active Member
When I had my 210 Select - cornering would take off speed - so trim needed to go down a bit while turning. It became 2nd nature after a month or so and I just did it by reflex from then on.
But make the performance base line chart anyway- it is really a nice reference for future use and prop comparison. With that you can always go back and compare. If you go in to a Pro prop shop - they like charts like that
If you don't do it - all you have is "gut feeling". And gut feelings can sometimes be influenced on what you just ate or drank
Although I wasn't able to make a complete baseline chart (water was extremely choppy), I was able to test out how my boat performs today when pulling a tube and/or whipping around sharp turns. I made sure to keep the trim down the whole time and wasn't able to get it to act up. I drove it fairly aggressively too, more so than ever before. With that, I wasn't able to get it to act up at all. I'm just going to assume that it actually WAS user error and that I had the trim partially up causing ventilation. Thanks for your input guys! I will be sure to complete my baseline chart during next splash day. I only have the lower speeds/rpms noted.
J
J