sportjet noise modifications

[Tagster]

Has anyone made any changes to the engine box of a sportjet to lower the noise level in the boat?

I think that Dr. Strangelove was going to install sound deadening matting on the inside of the box. Did it work? What about heat dissipation through the insulating material?

Motion Marine makes two exhaust pipes that run off of the ??? I have seen them at the boat show, but, they want $300 or more for the set.

Any ideas that worked? How about those that didn't?

Took some people from out of town on a Willamette River Cruise yesterday and couldn't even talk to them with the engine running.

Thanks for your help!!

Tag

[Pete]

I've got a sportjet. My "dog house" is lined with foil backed insulation. I guess it helps a little. I keep looking at the exhaust mufflers. Motion Marine quoted me $550 for a pair. Mercury sells them for $388 a pair, installed. I suspect those are the best method for reducing noise, but the cost for $0.11 worth of painted potmetal is exhorbitant, so I refuse to pay it. Maybe I'll make something with an old coffee can. :wink:

[invader]

maybe try puting in a nice quiet outboard with a prop. just a thought.

[Ed]

I have a 19' DW with a sportjet and the noise isn't too bad. The sides of my boat are carpeted throughout (not the floors) and the motor box is fully insulated on the inside and carpeted on the outside. I think the carpeting really makes a difference especially on the sides. I have buddy who has a Stryker w/SJ and it is very loud. His boat does not have any carpet anywhere. I to talked to the folks at Motion Marine about their SJ mufflers. The consensus was that mufflers would only be a benefit for people NOT in your boat. Anyway, my SJ is reaally quiet at anchor or with the kicker running. If I would of bought a V6/8 I would be complaining about the lack of room.

[TundraIII]

Hey Tagster, are you saying that you have NO insulation material on the inside of your
box? I have a Motion Marine boat and the engine box has a foil backed insulator on the
inside, carpeting on the outside and a padded top seat cushion. Still a little loud but not annoying at all. I probably could improve on this set up with the addition of a foam gasket around the bottom and back side of the box where it meets up with the floor and transom. I have absolutely no heat problems the way my box is set up. It wouldnt take but a few bucks and a couple of hours to modify your box if it isnt insulated. I would think you'd hear an improvement.

[Tagster]

There is no insulation at all in the doghouse of my NR. There is carpet around the outside and a pad on top, but inside there is only a thick coat of paint.

Would sound deadening matting (the type for cars with high end after market stereos) be better than foil back insulation?

Has anyone here actually tried the exhaust pipes?

Thanks for the replies!!!

Tag

[WaterDog]

No insulation?!?!?! :rolleyes: I would be very concerned there is no insulation on the inside of the motor box if you store your boat outside. It’s like having a metal or fiberglass canopy on your truck without the carpet. It’s going to sweat and that moisture cannot be good. Maybe it wont sweat too much with the carpet on the outside. :whazzup:

The MM mufflers do help but I don’t think it’s going to get you where you want. If I’m making a long run I just close the drop curtain. That makes more difference than anything I know of.

Too me, the SJ is not any louder than a 200 OB w/ a jet. I’ll also add that the last two weekends I had the opportunity to fish out of an inboard (Chev V-6 w/ AT pump) and I didn’t think it was much quieter at cruising speeds . The tone of the motor was different (lower), but we still had to talk just as loud to hear each other. :rolleyes:

[TheRogue]

Foil back is probably reccommended for the heat aspect.

[Grass Hopper]

Sound deadening insulation is a good Idea. But STAY AWAY FRON AFTERMARKET EXHAUST> I don't know if Motion Marine has an exclusive with Mercury, BUT I am a mercury dealer, and to the best of my knowledge a Non-mercury exhaust system voids the factory warrenty. (WAS TOLD BY THE LARGEST SPORT JET CONSUMER/MFG ON THE MARKET) GOOD LUCK!!

[WaterDog]

I do believe MM has the exclusive on those muffler's. :grin:

[Pete]

Mercury makes the mufflers. MM also makes a knock off version, but as stated earlier, if you still have less than one year on the motor, the warrantee may be compromised. Besides, the MM price is way higher than the Merc price, so why bother?

[Snake9t9]

There is an awsome product that is a heat insulator as well as sound deadener that is used in the street rod and custom car industry (small car, big motor, lots of heat and noise). It's called Dynamat. You can find it online, not cheap though.

[HOGTIDE]

Ya, without some kind of insulation or matting, your doghouse is just like a resonating bell or drum head. My Intruder SportJet has foil lined insulation on the inside and carpet on the outside of the box. The interior of the boat also has carpeting on the sides. The noise level has not been an issue at all. I know it's quieter than my old outboard jet and it 'must' be quieter than one of those river-shakin' big blocks!

Snake9t9 sounds like he's got a lead on a good product. Or, take the boat back to NorthRiver and tell 'em that they "forgot something important!"