Author Topic: Boats with water jet motors  (Read 3175 times)

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Offline tazman

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Boats with water jet motors
« on: August 19, 2004, 08:42:31 AM »
Been thinking about getting a Lowes 18' with a Honda or Yamaha 4 stroke jet drive. Was wonder if the ones that use them could give a little advice on what to look for and what to expect in the way of performance and how I should have one set up? :cb3:
Thanks Jack

Offline Darrell Davis

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Boats with water jet motors
« Reply #1 on: October 10, 2004, 02:08:17 PM »
:D Hey there Tazman,

As this is an old posting, not sure if you are still out there.

However, there are a lot of jets used in my area. More inboard then outboards.

You need to figure about a 1/3 loss of proformance with a jet as compared to an outboard with prop.

As I have personally not had a boat with a jet unit, my impressions are those of an onlooker.

It seems to me that outboard jets are noisy!!!!!!!!!! Not that inboards are not, but the outboards are worse with the sound being higher pitched with the 2 cycle eng.

How does that work out with the newer 4 cycle motors? Don't know, but I would expect the 4 cycle to not be as good in the power to weight dept., which might mean a 4 cycle with a pump might be overly heavy or under powered on a smaller boat.

As I am moving towards the time of retirement, I hope to again get an aluminum boat and possibly because of the waters I fish for Salmon and Steelhead a jet might be in the picture. Providing we can still afford to buy fuel for such things. So, I would be interested in anything you may have turned up.

Keep em coming! :wink:
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Offline Sourdough

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Boats with water jet motors
« Reply #2 on: October 12, 2004, 07:20:41 PM »
I run a Lowe 16' Oly Jon.  I have twin Merc 35s with jet pumps.  That's 70HP on a 16 footer, that's what it takes to get around.  My partner has an 18' Lowe with a 65HP Johnson with a jet.  I don't care what anyone tells you about losing a little HP due to the Jet, our rule of thumb here in Alaska where everyone runs jets is you lose 50 per cent.  When it's new you lose 40%, as it ages and the impellors get dinged and wear it increases to 50%.  Then one day you notice you don't have the usual power you check and you,ve lost 60%.  You dress up the impellor and move the washers to decrease the gap between the impellor and sleeve, you're back to 50%.  You do that a few times and it's time for a new impellor and sleeve.  Of course we run our boats hard and in some places you would only think an Air Boat could go.  We suck a lot of gravel and sand.  Especially when we are hauling out a Moose or big Caribou.
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Offline Darrell Davis

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Boats with water jet motors
« Reply #3 on: October 14, 2004, 04:53:17 PM »
:D Hey there Sourdough,

Interesting information, Thanks.

Sure would like to get up your direction for a B I G  Moose or a Caribou, but time is running faster then money and don't think I am going to make it.  Will be lucky to even make it for a fishing trip let alone a hunt.

Did get to take my once in a life time bull moose here in Ol'Ideeho a few years ago, and considering our moose are the smallest of the three varities they are still big and a lot of work to get on the pole.

Hope the fellow who started this post gets back to read your "been there done that," information on the jets

Would like to build my own welded aluminum boat. Wide and deep and not more the 18'. If I get to do so, not sure as yet what kind of power to go with. Don't plan to do the wild water, as there is plenty of good fishing without going to the extreme. If it happens, it will probably be after I retire a few years from now.

Thanks for the come back!

Keep em coming! :wink:
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Offline srwshooter

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Boats with water jet motors
« Reply #4 on: November 24, 2005, 12:50:08 PM »
i have a 1754 rhino built by jamesriverjets in va. with a merc 125/90 jet

here's mine and a friends 1660 with a 90/65 jet
http://i10.photobucket.com/albums/a126/srwshooter/2jets.jpg

these are great boats ,they run in about 4inches on plane,duel rod lockers ,stick steering ,lots of storage. .125 bottom thickness
here's another shot of mine.
http://i10.photobucket.com/albums/a126/srwshooter/P1020043.jpg

Offline Darrell Davis

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Boats with water jet motors
« Reply #5 on: November 25, 2005, 08:16:32 AM »
:D Hey there srwshooter,

Me thinks you need to park that boat at my house for a year or ten.

Looks like it would do real good on the Clearwater River in Ol'Ideeeeeho!

Bought time to put the shoot'in irons away in favor of Steelhead!

Keep em coming! :wink:
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Offline bilmac

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Re: Boats with water jet motors
« Reply #6 on: May 26, 2008, 08:50:08 AM »
With gas at $4 headed for$10, think about how inefficient jets are. The sourdough is right, unless you absolutely have to have them, they will cost you.

I used to do law enforcement on the lower Colo river where the "cool" crowd ran around in fancy high powered jetboats that burned 20 gal an hour. We routinely ran down boats with large V-8s using our 115hp outboard. The only ones we couldn't catch were nitro injected, you could tell because you could smell it in their wake.

Offline revo

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Re: Boats with water jet motors
« Reply #7 on: June 25, 2008, 12:44:15 AM »
Hey tazman. I'm in the market right now for the same kind of thing. Two things I can share from a newbie shopper perspective:

- Do not skimp on horsepower with a jet. Plan to go with the largest the boat will accept.
- Sea trial, sea trial, sea trial. Try before you buy.
- [And like others have said] only go with a jet if you really need one for shallow water.


Offline Rex in OTZ

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Swapping prop a jet drops the motors rated Hp by 30%.
« Reply #8 on: June 25, 2010, 10:19:54 AM »
I have a outboard jet foot that this season needed to be installed on a new Yamaha F40 prop motor, first off was the water pump needed to be modify'd to cool the F40, theres a difference in water pumps between prop and jet motors for 4-cycle yamaha's the same pump is used but they drill a relief hole in the jet equiped 4-cycle, the installation manual from 2003 showed the size drill & hole location.
When going from prop to jet and useing a prop motor this rases's a whole set of issues like transom riser plate and support out riggers and longer quill shaft and longer control/shift cables.
one is better off to buy a jet drive motor that dosent require the riser plate as the motor's that have props have a longer midsection between the power head and foot.
The www.outboardjets.com covers allot of the Frequently Asked Questions.

They recommend against useing a lever type grease gun, excessive pressure will invert the grease seal lips & no longer keep water out the the bearings.
useing any grease of NLGI #1 consistency witch is water resistant (main thing is keeping grease in bearing cavity water out)

Offline Rex in OTZ

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Re: Boats with water jet motors
« Reply #9 on: June 25, 2010, 10:23:19 AM »
Serviceing the Phantom sport jet (inboard Mercury 210) jet assy.
Helps to get the shop manual, and buy the impact socket to remove the impeller retaining nut
Its impacted on due to the high vibration's involved.
had to remove the reverse gate and cable support bracket's to remove the support houseing since my impeller was all rounded off and the impeller houseing was badly scored by gravel I replaced them (not cheap).
Up front of the inlet grill is the 90 degree gear box under the motor, pulling both plugs to service with recomended 75wt marine gear lube this model uses 24oz, the port side plug is the fill port, the Stbd side is the vent/witness hole, no water came out so the seal looks good for at least year (2004 boat from Comeau's of Fairbanks,AK) otherwise it looks like its a bear to change out the oil seal, Serviceing the jet houseing's can only be done with the boat out the water, the cone shaped houseing supporting the end of the impeller shaft contains 75wt marine gear lube with no bearings just a pair of oil bath bushings, this houseing does not have a low point drain plug due to the location inside the jet drive houseing. to remove old lube the is houseing should be removed and dumped, they do provide two plugs visible from the back end but only the top plug is used for serviceing the center one on the apex the cone is for draing off the boat, I'm contemplating useing a suction gun to draw the gear lube out at the next service schedule (100hr's hobbs time) or once a year the problem is not getting all the old lube out or water sitting in the bottom, both front and back lubes were dirty like mabe seal wipe since it was dark, no creamy/whitish water contamination was found, Thank goodness a pilot buddy let me use a hanger to do this as outdoors we have heavy blowing dust problem.


Offline Rex in OTZ

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Yamaha F series water pump mod Over cooling relief hole.
« Reply #10 on: June 28, 2010, 07:31:48 AM »
If you ever completely replace your water pump on a F-series Yamaha outboard jet remember they need to have a hole drilled in them so check if it has it done and if not make shure it does.

Here's information from the outboardjet company to modify the F series outboard jet outboards so as not to over cool your motor.