What can I do to make my boat go faster?

[Stumpalump]

Re: What can I do to make my boat go faster?

I love race gas! I burn 100 or 110 octane in a sand rail with a slightly tweaked supercharged 2.0 Chevy Ecotec. About 250 honest HP. Most boosted guys claim they detuned from 500 hp so they can run pump gas. They now claim 350 or so HP but the little Ecotec runs better, cooler stronger and faster. The reason is under boost the knock sensor pulls timing. If ice cold I bet they can hit 350 HP but after 1/2 hour my little 250 HP engine out pulls pulls them because of the race fuel. That's under boost so then what did it do when I dumped 2 gallons mixed with 8 gallons of pump gas in my 1985 Johnson 60? It ran a tad smoother and quiet. The smoothness allowed it to eek out less than 100 RPM on the top. Slight improvement on the boat if you can even call it an improvement but under boost in the rail it's like Wow. In my Honda XR 400 dirt bike the race gas runs better but it lost power. The difference between 87 and the 91 at the pump is negligible. It's got a better additive package and since the octane falls out of modern fuel in 30-60 days I might as well run it in the boat for the $3.00 extra dollars it cost at fill up.

18:1 oil in an air cooled two stroke is the most dyno power you can get if you jet for it and in hydroplane racing they run 25:1. To the average joe this all means nothing but if tiny improvements by tinkering put a smile on your face then by all means have some fun. Heck I just port matched my carb and air silencer gaskets last night because they blocked a bit of air flow. How much do you think that helped? Nothing...but when my 34 mph boat hits 35 with a tail wind I'll smile ear to ear!

 

[snowman48047]

Re: What can I do to make my boat go faster?

I have a 1440 jon boat that I use for fishing and duck hunting. It has a 9.8hp motor with factory prop. With just myself in it (175#) and some duck decoys, it will go about 15 mph at WOT. I had my 225# hunting buddy in the boat with me and we were crawling at 8 mph. I'd like to go at least 12 mph.

What can I do to make the boat go faster? Will a jackplate make that much of a difference? Will a 15hp motor get me the speed I need? Any other ideas?

If you are rated for a 20 then get the bigger motor. That being said, as a duck hunter I have to ask;

You have 14' jon boat, flat bottom, with no keel, a 225# buddy plus his hunting gear, you = another 200# plus added gear, plus decoys, and you want to do 15mph? What is your hurry? Are you one of those guys that like to show up AT shooting time? What is your weight capacity? You probably have 600+ lbs of "stuff" in the boat. How much freeboard do you have with the boat loaded? Are you hunting potholes or big water? Safety is the big issue here. Going fast in Oct-Nov with 45 degree water temps aint smart in a heavily loaded boat.

 

[GHBAY]

Re: What can I do to make my boat go faster?

you havent mentioned colour... from my experience, if you paint it red or yellow it will speed up a bit

 

[rallyart]

Re: What can I do to make my boat go faster?

Stumpalump, most racing fuels are rated on Research Octane only and not the R+M method of pump fuel so the numbers are not always as impressive as what is stamped on the drum. If you want to get a cheaper boost you could just add straight toluene to your pump gas. It has a higher rating and does not go through the same distribution channels. There is a pretty complex science in building real racing fuels. In Formula 1 they run 4% dissolved Oxygen to increase the amount of power they can generate. I've run many dynamometer tests on engines to find out what 'tweaking' works and what does not. There is no power gain from using a fuel not optimized for your engine, unless there is a problem with the engine.
Taking the time to try some of the changes you suggest can be fun to those with a knack, and can help set up any vehicle for an improvement. If you don't have that knack it can create problems. It's like the guy who feels his engine runs better now that it is louder when all he has is a hole in his manifold that is slowing him down.

I agree GHBAY. I think dark green is the slowest.

 

[crabby captain john]

Re: What can I do to make my boat go faster?

Hang a 115 HP motor on the back and hold on~~ well swim as it will sink, but it will sink fast. For your purpose you need a bigger boat with a bigger motor or a lot less gear and go alone. A 20 hp may work, but not greatly either

 

[Stumpalump]

Re: What can I do to make my boat go faster?

Stumpalump, most racing fuels are rated on Research Octane only and not the R+M method of pump fuel so the numbers are not always as impressive as what is stamped on the drum. If you want to get a cheaper boost you could just add straight toluene to your pump gas. It has a higher rating and does not go through the same distribution channels. There is a pretty complex science in building real racing fuels. In Formula 1 they run 4% dissolved Oxygen to increase the amount of power they can generate. I've run many dynamometer tests on engines to find out what 'tweaking' works and what does not. There is no power gain from using a fuel not optimized for your engine, unless there is a problem with the engine.
Taking the time to try some of the changes you suggest can be fun to those with a knack, and can help set up any vehicle for an improvement. If you don't have that knack it can create problems. It's like the guy who feels his engine runs better now that it is louder when all he has is a hole in his manifold that is slowing him down.

I agree GHBAY. I think dark green is the slowest.

I've heard about the toluene trick but my problem is that the Arizona heat degrades ethanol pump gas really fast. Oxygen enhanced race fuels have a problem with going bad as well. Not rocket science because an oxidizer creates oxidation and in time it just oxidizes and rots the fuel. It does add real power when it's fresh. It's just too bad I can't buy pure 93 gas anymore. Generally I just buy AV gas. It's got enough octane and is designed to last for years. It's good for the chain saws and weed eaters that sit for months. I just found 110 Sunoco for $7.50 at a Loves truck stop of all places. A wise man once told me to buy the right fuel not motors. The guy that dyno's my rail said to run it as well. I have not blown up an engine or been into a carb that I run on the good stuff in a decade. Knock on wood.

 

[haulnazz15]

Re: What can I do to make my boat go faster?

I agree GHBAY. I think dark green is the slowest.

There are probably some Jag owners that would like to argue that one. :laugh:

 

[Campylobacter]

Re: What can I do to make my boat go faster?

What kind of motor is it? In some brands, the difference between a 9.9 and 15 is mainly the carb and prop, you might be able to "upgrade"

 

[snapshotmd]

Re: What can I do to make my boat go faster?

What kind of motor is it? In some brands, the difference between a 9.9 and 15 is mainly the carb and prop, you might be able to "upgrade"

It is a 1982 Mercury. I checked about swapping carbs and this motor is maxed; for this frame there is a 7.5 and 9.8.

I think what I'll do is wake up earlier when hunting with someone else. The boat is kind of maxed at that point; 455 people/780 total. But I'll try shifting things around to get a better attitude and look out for a good deal on a 15. Maybe I'll lift the motor up an inch to see if that helps.

 

[Scott Danforth]

Re: What can I do to make my boat go faster?

you can try and ventilate your prop, it helps a bit to get it on plane by getting the RPM's up.

 

[26aftcab454]

Re: What can I do to make my boat go faster?

Hang a 115 HP motor on the back and hold on~~ well swim as it will sink, but it will sink fast. For your purpose you need a bigger boat with a bigger motor or a lot less gear and go alone. A 20 hp may work, but not greatly either

I used to have a 18ft aluminum boat with a 115hp.
a 15 or 20 hp motor is what you need.

 

[steelespike]

Re: What can I do to make my boat go faster?

delete

 

[steelespike]

Re: What can I do to make my boat go faster?

You need to be sure the motor is in excellent tune and throttle is opening all the way.Do you know the gear ratio?
If you get us the prop size,(near the base of the blades or on the end of the hub) and a lightly loaded gps speed we may be able to guess the rpm and a possible prop size.At over 700 lbs you surely need a little less pitch.Carefully trimmed and lightly loaded you should approach 20 mph. Your also struggling with a boat that is a little too small for the load.It's very likely a 14/48 might plane with the same load do to the larger foot print .I believe your 82 if above ser. no. 5206549 is rated for 5000-5800 rpm.I have a feeling that at 15 mph your not any where near max rpm.
Did a little calculation; assuming a 8" pitch,2.00 gear ratio at 12% slip and 15 mph rpm would be about 4500 rpm. Way too low assuming a light load. I'm guessing prop size and the 12% slip. 8 to 12 is pretty normal.

 

[alex24456]

Re: What can I do to make my boat go faster?

Strip the boat or don't take a mate
- dead weight

 

[NSBCraig]

Re: What can I do to make my boat go faster?

Smart tabs will help you out big time.

 

[Baylinermike]

Re: What can I do to make my boat go faster?

Throw a 1/2 inch block under the motor (where motor meets transom) might get a mile per hour. I use a foot long piece of oak hardwood flooring and my 10' inflatable with a 25 merc hits a touch over 40mph. Worth a shot, and its basically free!