lowering minimum planing speed

sly_karma

sly_karma

Crew Member
I want my boat to go slower! Well, I want to be able to stay on plane when choppy conditions force me to lower speeds. It's a 19.5 ft fibreglass medium V with a 140 hp outboard and will stay on plane down to 19 mph. Any reduction in throttle from there drops speed to 13 mph and the engine is wasting loads of fuel pushing water. The difference is dramatic, respectable 3.5 mpg on plane, but a thirsty 2.0 - 2.2 mpg off plane. The boat gets on plane quickly, trims level easily and has ample top end speed, 38-40 mph depending on load and conditions. It's reducing the minimum plane speed that interests me most.

From what I've read so far, my options are helm-adjustable trim tabs, smart tabs or engine leg hydrofoil. I'd like to hear user experiences about what I can really expect - is it possible to reduce minimum planing speed to 13-14 mph?
 
4 blade prop. quick out of hole lower top end and plane at lower speed. Did it for me on 23' Grady.
 
hydrofoil's work well for a minimal investment.
trim tabs would be better if you want to spend the money.
 
I have 21 foot Seaswirl and it has tabs and a hydrofoil. I use very little tab only on one side for levelling but the foil really lets me stay on plane as low as 12-13mph. Each boat set up will have different results of course but it works well on my boat....
 
Don't get the smart tabs. Waste of money. They do get the boat up on plane faster but you can't adjust them and you can't back up cause they are in the full down position at idle.
I installed Bennett trim tabs on my 21 footer and really liked them. Let's you adjust for list and also push the bow down when it's choppy. I would think they would help you stay on plane if pushed down at lower speeds.
You do have to drill a couple of holes right through the transom so not for the faint of heart.
Probably a half to full day project.
Sounds like the foil might be your best bet to start.
 
Don't bother just put a hydrofoil on. I can't believe how much difference it is having it...I run a mecruiser 3.0l and it's amazing I can get up on plane below 3000 rpm..I couldn't do that before..Also on turns the butt won't slide out anymore..I know you can put everything on but for 100.00 I was amazed something so simple can work so well...
 
Been down this road lots of time over the years with many different boats…….
In my experience the order of effectiveness is,
1) Trim tabs
2) Propellors
3) hydrofoils
This list dosnt factor in cost just which worked better in my experience.
Trim tabs also have a host of other benefits that make them a necessary item on all boats over 18-19' IMO
 
I agree that a 4 blade prop would help some. Try a solus Amita for about $150. I had a similar problem with a 19' Starcraft that prop helped. But for another $150 put on the smart tabs. We installed them and went from planing at 19mph to planing at 12mph. What smart tabs have over a hydrofoil is less pressure on the leg itself and also you get better side to side stability. We had a heavy kicker on one side of our boat and with a hydrofoil the stern would lift up and then lean over on the heavy side. With smart tabs we set one side with a higher level of pressure to adjust for the weight bAlance. Once you have set them up you never touch them again. Make a huge difference in the way the boat handles rough conditions. Smart tabs are a good inexpensive option and you can still reverse but I guess not as fast.
Install on smart tabs is pretty easy

The best and most expensive option are bennet trim tabs at about $700 plus install that is quite a bit more work and expertise neededto install than smart tabs.
 
Installation of tabs I can handle, have a good shop and tools and enough background. I'm a bit leery of changing props at this stage of the game, would add a bunch of other consequences. I'm happy with gearing on the standard prop, revs out to 5100, holeshot is fine, planes within seconds.
 
Bought a hydrofoil today. For under $150 it's worth a try. Plus my transom is crowded, if I go the trim tabs route I will need smallish ones to make them fit, lift from the hydrofoil should help make that work.
 
Put a set of 4 blade props from King propeller's out of California, on my Sea Ray 270 and made a huge difference. Used to have to sit on about 21 knots to run out off shore. Now can sit at 16 if rough and stay up nicely with 4 people on board.
 
I have been considering adding a hydrofoil to my boat also. It is a 16.5' Harborcraft with a 60hp engine on it. For most of my use I have no issues getting up and planing and fine with the speed too. The issues for me come up when there is 4 guys on board or when loaded down going camping. From what I understand, the hydrofoil will help get up and stay up on plane in those conditions.....but will it negatively affect top speed or fuel economy for the other 90% of the time?

Thanks, AP
 
Before this thread, I wasn't aware that 4 blade prop could have this affect. Need to do some reading on prop theory!
 
Hey Andrew P , i had a 15' aluminum and had a hydrofoil on it and it made a huge difference in .. up on plane quicker and staying up at lower rpm , i noticed a difference in gas much better , Now i've got a 16 Harborcraft also with a 50hp and just purchased another hydrofoil for it this morning from westmarine . i wouldn't go without Huge difference.


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Andrew P said:
I have been considering adding a hydrofoil to my boat also. It is a 16.5' Harborcraft with a 60hp engine on it. For most of my use I have no issues getting up and planing and fine with the speed too. The issues for me come up when there is 4 guys on board or when loaded down going camping. From what I understand, the hydrofoil will help get up and stay up on plane in those conditions.....but will it negatively affect top speed or fuel economy for the other 90% of the time?

Thanks, AP
Click to expand...
 
sly_karma said:
Before this thread, I wasn't aware that 4 blade prop could have this affect. Need to do some reading on prop theory!
Click to expand...

Contact King Props. The owner there was who spoke with me on the subject and fixed me up. It preformed exactly as he said once installed. Very pleasant to deal with and good prices. Look them up on the net.
 
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