outboard jet question

[JoshKeller84]

hi, guys, i currently have a 2001 3 cylinder johnson 35 hp loop charged 2 cycle. my boat is a 2013 alumacraft 1648 modified v, riveted hull, approx 300 lbs. 2 trolling motor batteries, and a 24v trolling motor. approx package weight is 600 lbs. im interested in a jet pump or jet motor for this boat, but id like to still be able to use a prop lower as well for lakes/rough water. my boat is rated for a 35 hp max. ive called a few boat dealers asking for advice, and they seem to think my 2 stroke 35 hp will be fairly closer performance wise with a jet to a 40/30 4 stroke. I have been told my 35 puts out a few more hp than 35. I also see that the new merc 25 jets, are actually 30 hp power heads.

my boat now runs 32 mph, instant hole shot. i have had a 25 hp prop on and it did 27 mph with two people and planed out easy.

if i get a jet pump for my motor (they are available), will i get on plane with me (200 lbs), and another 150 lb fisherman? im not worried about breaking 30 mph or anything close, i just want to be able to plane out and fish shallower areas of the potomac 5 - 10 times a year.

 

[crabby captain john]

Re: outboard jet question

Change the 35 to a jet and performance will suffer. Probably like a 20hp - 25 hp. Getting on plane with the 2 people, batteries, fuel, and other equipment is questionable. Add another battery and a trolling motor would be less expensive and not much less on performance.

 

[Bob_VT]

Re: outboard jet question

A jet drive on an outboard takes away up to 25% of the horsepower and is no where as efficient as a prop.

Probably the best thing to consider is a small outboard...... say a 5 to 9.9 hp and carry it along with you. When you get into skinny water mount it on the transom and slowly make your way in. If it is an area plagued with weeds then neither a jet or an prop will work well enough.....then you row or pole yourself out.

 

[Outsider]

Re: outboard jet question

I had a similar-sized boat with a 50 jet. Performance with two plus gear was "OK", but just so. You'll find a 35 to be underpowered, but might be OK for occasional use. Your fuel burn will go up exponentially with the jet, and performance will suffer as loading increases. Jets are also extremely sensitive to water flow restrictions, like weeds on the inlet grate. I had mine for 3 years, had more fun than monkeys with a football ...

 

[steelespike]

Re: outboard jet question

Being less effective the jet will use more fuel.Your 35 will still use about 3.5 gallons per hour at wot but will require a higher throttle setting for any given speed than that of a prop drive thus the higher actual fuel use.

 

[JoshKeller84]

Re: outboard jet question

i'm aware of all the short comings of a jet - thats why i would like to keep my 35 prop. if i go to a 50/35 or a 40/30, my boat becomes illegal if i run a prop drive, due to my max horsepower rating of 35. my biggest concern is planing out with the 35 if i get a jet pump, as i will not be using the jet all the time - more of a need it to get to certain areas we fish 10 or so times a year.

 

[bilge rat jim]

Re: outboard jet question

i'm aware of all the short comings of a jet - thats why i would like to keep my 35 prop. if i go to a 50/35 or a 40/30, my boat becomes illegal if i run a prop drive, due to my max horsepower rating of 35. my biggest concern is planing out with the 35 if i get a jet pump, as i will not be using the jet all the time - more of a need it to get to certain areas we fish 10 or so times a year.

Why does this make your boat "illegal"?

 

[JoshKeller84]

Re: outboard jet question

i usually use my boat in maryland, and they tend to try and find any reason they can to take your money. running a boat with a motor over the max hp plate is one of those reasons. not to mention the liability aspect, and the inability to keep it insured.

 

[Frank Acampora]

Re: outboard jet question

All the newer jet outboards I have seen are marked with the jet equivalent horsepower. It doesn't matter what engine block the factory put under the hood, the factory will rate it as jet power and the engine ID plate will comply. THUS a 50/35 will be a 35 horsepower engine and your boat will be legal.

 

[ondarvr]

Re: outboard jet question

The official power loss is rated at 30%, but from experience I'd say that's an optimistic estimate, it's more like a 40% to 50% power loss in actual performance. I had a 16' G3 at my place for a few years with a 60/40 on it, it was a great match, others use a 50/30 on them and it works OK, at 35/20 you would be right on the edge of getting on plane. With just you and a light load it would probably get on plane, add a guy and it?s a maybe, I've seen it work, but not on every hull, adding extra batteries, a trolling motor, cooler, anchor and other stuff and you will not be going anywhere fast. When and if, you do get on plane the throttle will most likely be wide open to stay there.

Jet pumps are very sensitive to the exact hull and motor used, so you won't really know until you try it, but it's a rather expensive experiment.

I have a jet boat about that length only heavier, it has a 90/60 on it.

 

[JoshKeller84]

Re: outboard jet question

All the newer jet outboards I have seen are marked with the jet equivalent horsepower. It doesn't matter what engine block the factory put under the hood, the factory will rate it as jet power and the engine ID plate will comply. THUS a 50/35 will be a 35 horsepower engine and your boat will be legal.

understand that, but i want the option to run prop most of the time - thus limiting myself to 35 hp at the prop. looks like i may just ahve to pick up another boat for a jet - preferably welded.

 

[cinqzero]

Re: outboard jet question

Hey there.
I run a 16' Princecraft Springbok at work.
It weighs about 300lbs.(I think)
It has a Yamaha 4 stroke, electric start 30/40hp jet.
It is a 40hp power-head and is rated at 30hp. It weighs about 200lbs.
Boat Rated for 30hp.----Jet is rated at 30hp by manufacturer I believe. So ok by me!
It gets up on step and goes good.

A more extreme example:
With my work mate, 8 deep cycle batteries and some tools we managed to get it up on step.
Part of this is horsepower, part of this is probably from the relatively flat and wide bottom and hard chines.
We were overloaded and only had to run 100meters or so but the boat did get up (I was pleasantly surprised).

For all other times I've been in it, it has been fine and pretty responsive.

I like jets but if you really want to know about outboard jets, go to the "source of all" their website.

Outboard Jets - Make Every River Longer

They make all the jets for all the different outboard manufacturers. Invented the things.
They have a good FAQ page (this is mandatory reading in my mind)you can download and I found them helpful on the phone.

Personally I like jets because they are simple to maintain, and pretty much bombproof.
You have to remember that with jets, horsepower is king---always. There is no swapping props for different pitch(stainless 4 blade impellers maybe depending on HP engine).
Your hull design matters too of course, but look at the FAQ sheet before you decide to buy.

Good luck.

Trevor

 

[JoshKeller84]

Re: outboard jet question

i know this has been beat to death, but what are your thoughts on this chart? the 4 stroke yamaha 40/30 pushes this 800 lb bare hull/1500 lb package to 27 mph. wouldnt my 35 3 cylinder push a 700 lb loaded boat similar? my biggest concern in this investment is being able to get on plane. if its slow, i can deal with that, as long as i can run shallower than with my prop. if its 20 mph but stays on plane, im okay with that. this is simply for a once in a while fishing areas, 90% of the time i will be running my prop set up.

http://www.yamahaoutboards.com/sites/de ... 13_alm.pdf

 

[Mi duckdown]

Re: outboard jet question

What cinqzero posted. GO to there website, then call them FOR ALL YOUR QUESTIONS. Simple, They are the Gurus. Nice people.