9.9 Big Foot/Pro Kicker Too Slow/Prop recommendations?

I have a Pro Line 241 WA that weighs somewhat over 5,000 lbs. when loaded.
I have a 2006 Mercury 9.9 Big Foot Pro Kicker mounted on the a metal bracked right to the factory swim platform. At idle ( 600-700rpm) the 9.9 will not even push the boat a half of a mile per hour in calm wind/sea conditions. I troll mostly for lake trout on Lake Superior at 1.7 to 2.4mph depending on various conditions. Occassionally I will troll for salmon from 3.5 to 5mph, but I would use the main 250h.p. io for that in most cases, but in some cases might want to use the 9.9 for that trolling.

I find that when I am even trolling for lake trout at modest speeds the 9.9 is probably running faster than it needs to. But also when using the 9.9 as an emergencey back up kicker, it is a bit slower than I want it to be under any siginficant headwind conditions. At 5000-6000 RPM, which is WOT, it will push my boat about 6mph.

In a fairly steady 25 mph headwind, it will barely push the boat 1mph, or so. I encountered a wind condition last fall like this and it took me a long time to get back to port. I know that this is a significant headwind to be trying to head into. I could have traveled down or side wind to reach shore, but did not want to beach the boat on rocks. But, my kicking speed performance is secondary to my need for faster trollin ability at lower engine RPM. A somwhat faster kicking speed performance would be nice to have as a byproduct of tweaking the prop for trolling.

The factory aluminum prop is fairly flat at a 10" dia, with a 7" pitch. I would like to increase my speed(distance traveled) by at least 30 to 40%. My marine mechanic says he has a Mercury outboard prop that may fit my boat that I could try, and it will increase the size of the dia. to 10 3/8", with a 9.5" pitch. This will cause the boat to travel an addtional 2.5 inches per prop revolution, he claims, which is a little more than 25% of an increase in distance traveled per revolution, which directly results to the same relative increase in speed.

Like I mentioned earlier, I may want to have a little more increase in speed, whether it be for kicking me back quickly from bad weather should my main engine die, or just for running the engine RPM a little slower when I am trolling for lake trout. Even if I doubled my distance traveled per prop revolution, I think I could even troll for walleye at 1mph or less, as the boat may go .4 mph now at idle according to my estimates.

The question is, how much should I reasonably bump up my pitch to have a resultant longer distance traveled per revolution in my application? What are the negatives of increasing by 25%, 35%, or up to 50% or more my effective distance traveled per revolution with this high thrust 9.9 motor. I believe the gearing on this 9.9 Big Foot was oriented toward helping lighter/smaller boats achieve slow trolling speeds needed for walleye trolling. It is good at that, but too good/slow for my application.

I have priced the large 15h.p. Mercury Big Foot and it is in the high 3,000 dollar range. I would like to avoid buying one if I can come up with a prop solution. The 9.9 seems to have gobs of torque and resultant thrust for my boat. I just feel that I need to gear it differently, and I hope that can be effectively done with the prop. Just need to know what the thresholds for neagative performance are when increasing distance traveled per revolution in my case.

A WOT speed in calm conditions of 8-9 mph would work well for me, which is at around 5500 rpm or more engine speed. I realize that as the speed increases to this 8-11 mph range the resistance to getting up on plane starts to exponentially increase at some point, thus causing the motor to work hard in pushing more and more water with the boat hull.

An RPM of around 1800 at 2.2 mph would work also sem to work well. At 1800 rpm now, I think I am probably only traveling 1.2 mph.

At 3000 rpm I think I might be traveling at 1.8-2mph. If anyone has any specific recommendations or feedback, I sure would appreciate hearing from you.

Thanks,

Clay Adams

Re: 9.9 Big Foot/Pro Kicker Too Slow/Prop recommendations?

A 9.9 on a 5,000 lb boat;kind of like having it mounted to the dock.
Do you know it is turning 6,000.A think a 9" prop will drop your rpm close to 600 to 800 rpm, pushing that weight.When you increase pitch you lose power I don't think the motor can make up the speed especially with a wind.Won't cost much to try a 9" prop.I think 8-9mph isn't likely.You may gain a little in light weather but I think the wind will knock it down quickly.If you don't run wot all the time I guess the motor will be ok.

Re: 9.9 Big Foot/Pro Kicker Too Slow/Prop recommendations?

I currently use a Yamaha T9.9 high thrust for my troll motor for salmon trolling on my 23 SeaCraft and it does ok. I use to have a Honda 15 hp and woorked ok for trolling also, but it also was 2-3 mile per hour fast than the T9.9. The big foot is a Tohatsu motor painted black, but the main difference with mine and probably yours is the gears in the lower end so you don't get as much speed as you do thrust for the bigger prop. Kinda like a truck with 4:11 vs 3:55/327 Gears. Lots of power but less speed. If you need more speed and decide on a bigger engine I would recommend going up to a 20 HP.

Re: 9.9 Big Foot/Pro Kicker Too Slow/Prop recommendations?

steelespike said:

A 9.9 on a 5,000 lb boat;kind of like having it mounted to the dock.
Do you know it is turning 6,000.A think a 9" prop will drop your rpm close to 600 to 800 rpm, pushing that weight.When you increase pitch you lose power I don't think the motor can make up the speed especially with a wind.Won't cost much to try a 9" prop.I think 8-9mph isn't likely.You may gain a little in light weather but I think the wind will knock it down quickly.If you don't run wot all the time I guess the motor will be ok.

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I will not run it WOT for any reason that I can think of other than an limited emergency scenario if it is needed. My marine mechanic will let me borrow a 9.25dia. by 9"pitch, a 9.5"by 8"pitch, or a 10 3/8 by 9.5pitch to try them out without any obligation to buy, as long as I don't bung them up on a rock or something. If we can find what works well, we can also have my current 10"by 7" pitch prop modified a bit. One way or the other I will see what combination works well. I would like to take the trial and error out of the process ahead of time if possible. My mechanic has some experience with props, but he is not expert.

Thanks for your comments.

Clay

Re: 9.9 Big Foot/Pro Kicker Too Slow/Prop recommendations?

gss036 said:

I currently use a Yamaha T9.9 high thrust for my troll motor for salmon trolling on my 23 SeaCraft and it does ok. I use to have a Honda 15 hp and woorked ok for trolling also, but it also was 2-3 mile per hour fast than the T9.9. The big foot is a Tohatsu motor painted black, but the main difference with mine and probably yours is the gears in the lower end so you don't get as much speed as you do thrust for the bigger prop. Kinda like a truck with 4:11 vs 3:55/327 Gears. Lots of power but less speed. If you need more speed and decide on a bigger engine I would recommend going up to a 20 HP.

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I am trying to make up for that difference in the gearing that you mention with the prop itself. I know it will not push like a 15h.p., much less a 20 h.p., but I believe I can get some margin of improvement before I resort to spending big bucks to trade up to the nearly 4000 dollar 15h.p. pro kicker. My friend has a 15h.p. merc. 4 stroke on his 2450 trophy hardtop, a 1500 lb. heavier and a larger boat than mine with a larger wind footprint/profile. His 15 does real well in trolling for him, but it does not have the same low end grunt thrust factor as mine with that gearing. However, his engine does not rev very high to troll at 2.0 to 2.5mph when lake trout fishing.

Thanks for your thoughts.

Clay

Re: 9.9 Big Foot/Pro Kicker Too Slow/Prop recommendations?

I hear what you are saying, but when you have a 10-20 head wind, it is extremely hard to make head way. Here with our big tides, it is like peeing in the wind, you just get a warm feeling. I was out last Friday and we had a 9.4 ft tide fall and there is no way you can make headway against that with a 23-25 ft 5000# boat.

Re: 9.9 Big Foot/Pro Kicker Too Slow/Prop recommendations?

gss036 said:

I hear what you are saying, but when you have a 10-20 head wind, it is extremely hard to make head way. Here with our big tides, it is like peeing in the wind, you just get a warm feeling. I was out last Friday and we had a 9.4 ft tide fall and there is no way you can make headway against that with a 23-25 ft 5000# boat.

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Lake Superior has no tide, but it does have a 1-2+mph current in the deep water next to rocky bedrock shoreline where I fish. The nature of the lake can cause unexpected squalls that can go from 12inch waves to 3-4 footers which are only in 15 minutes. Of course the wind is a whole 'nother matter that can be a challenge. I would rather have twin 125 h.p. four stroke outboards, but that have cost twice the price of my boat. I will probably some better margin of performance for trolling, but for powerful kicker use, I will get a lesser margin of performance by tweaking the prop. I am still looking for a larger Big Foot and see a 25h.p. listed for sale for a reasonable price, but it weighs in at 154lbs. instead of the 98lbs. for my 9.9, or of the 112lbs. for a Big Foot 15h.p., or about 120lbs for a 20h.p. Big foot. With the right deal, I guess I can upgrade, to get an ideal solution.

I agree about having sea/weather conditions easily overcoming a modest sized troller. These new four strokes have a ton more low end grunt as compared to the two strokes of the same size, but they run out of wind when trying to overcome intense wind, current, when used on a 5000 lb. boat. I own a low hour 35h.p. Evinrude two stroke that I could consider using for offshore trips as a kicker, and it would overcome most seas and wind if I get into some real weather junk with a failed main engine. However, I would need to have a good supply of mixed oil and gas on hand to make any long distance headway in that sort of situation.

But normally, I just fish near the coast, less than a mile off shore, so I am good with the 9.9. I would like to make a couple of long offshore trips to some reefs that are 40-50 miles offshore, so that would mean that a much larger four stroke troller/kicker would be needed in bad weather in even of the main i/o failing for some reason or other. I have had my i/o on this and another boat fail before, once from the shift linkage, and once from the coupler. My trolling motor (9.9) has gotten me home in both situations, and in both situations I had 20mph+ winds, and 2-3 foot choppy Lake Superior waves. On the Proline, though it took an hour to go 1.5 miles or so back to my home dock, where on my much lighter aluminum 19' Starcraft Holiday, with 4cyl i/o, it took me 15-20minutes to go a similar distance at around 4-5mph headway with near WOT. The Starcraft only weighs 60% of the Pro-LIne and it has a smaller wind/sail profile.

I like to be conservative when I boat, so I'll see what I can do with my prop tweaking. I may forego any offshore trips until I have a larger engine, or unless another fisherman takes out his boat with me for security. The problem with that though, is that if one of us gets in trouble, we might have to abandon the other boat in bad weather. I cannot see towing boats in 5-6 foot waves with wind...that would be impossible to do for 30 miles. Lake Superior can wip up 15-20 footers in storms, and the waves are spaced much more closely than ocean waves, maybe half the distance or less. Because of this, I need to make sure I can get back in a safe manner if things get crazy with the weather/sea conditions.

Thanks for posting. It makes me think wisely toward knowing my limits, in a conserative sense, something all boaters need to lean toward in their boating.
I once went boating with a captain that took too much risk with the weather, and we capsized in a storm and were saved by another boater that just happened upon us in the storm. One of my friends nearly drowned, and I had to untangle him underwater from some dock lines that were tangled underwater, one good reason to secure lines at all times on deck. Well, I will not go on anymore, but all boaters should take heed of risks, by making conservative risk assessments in their planning, including myself.

Safe and Fun Boating to You!