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Results of latest gmtech mods and A SHARK ON THE BOAT!!!!!

gmtech16450yz

Jetboaters Commander
Messages
270
Reaction score
530
Points
197
Location
SF Bay Area
Boat Make
Yamaha
Year
2017
Boat Model
Limited S
Boat Length
21
Ok I had a chance to take the boat out in the San Francisco Bay today. Amazingly nice ~72 degree air temps, water as smooth as glass day. The latest round of mods all worked awesome! and, I CAUGHT A SHARK!!!

Haha. I've been trying to catch one the last 2 times out in the Bay, finally got one today! OMG what a beautiful animal. It was like 5 feet long, not sure how much it weighed but it was pretty heavy! It's a Leopard Shark, pretty common in the Bay. We'd been fishing for a few hours already but when I finally hooked it and saw it in the water I didn't know what to do! I used a nice LONG pair of pliers to get the hook out, we took a couple pics and each of us had a chance to touch it before we let it go. So cool!

For those that were following my latest mods, the exhaust was WAAAAYYYY quieter, the engine noise was WAAAAAYYYY quieter, and my gauges worked perfectly. I was afraid adding in the Moroso Spiral Core mufflers might hurt power, but as usual, top speed didn't change a bit. Holding a normal volume conversation at anything below 7k rpm is not a problem, between 7 and 8k/52mph you have to speak up a little bit but it's still not bad.

The gauges worked awesome, as I thought, the lower ranged temp gauges are perfect. Highest temps I saw were under 150, "normal" seemed to be around 135-140 degrees. That's with 61 degree water temps. Interesting thing was that the port engine ran 5-10 degrees hotter most of the day. It's possible that the gauges aren't that accurate and the engines themselves actually aren't that far apart temp wise. The same was actually true for the water pressure gauges also, the port engine showed higher pressures than the starboard side. The explanation for that could actually be the fact that I opened up the nozzle on the starboard jet to equalize the engine rpms. A little less nozzle restriction could certainly explain the lower pressure readings. The cool thing is that 0-30 psi gauges are PERFECTLY matched to what our engines run at. Once you're over 3000 rpms or so the pressure starts reading. At 6800rpm the pressure reads about 20 psi, at 7800 the port side was reading about 28 psi and the starboard side was at 26 psi. So my idea of easily being able to make sure your pump pickup or coolant screen isn't plugged by simply glancing at the pressure gauges will work perfectly. Yay!

The blower mod also worked awesome, you can barely hear it when the engine is idling and the fans are on the low speed. On high speed you can't hear it once you get engine speed over 3k rpm or so. The other thing I did was to cover the aluminum pieces I made for the dash, throttle controls and storage compartment with white marine poly. I usually like polished aluminum, but it just didn't look right in a boat. The white looks much better imho.

It's so nice to have a boat setup the way you like it and the way it all just works the way you need it to. I put a bunch of hours into doing this stuff, but I'm thrilled with the results. The boat is quiet, fast, has the information and controls I need on the dash and looks good. The rod holders are amazing too! I really do like this boat, we should get many years worth of enjoyment out of it.


Screenshot_20180208-132335.png 20180208_090533.jpg 20180208_091308.jpg 20180207_204256.jpg 20180208_073832.jpg IMG-20180206-WA0003.jpeg 20180207_204248.jpg
 
Great catch. Your mods look good. Nice job.
I'm in Grass Valley and thinking of going out in the bay. How does your boat handle it? Do you take into the ocean?
 
Great catch. Your mods look good. Nice job.
I'm in Grass Valley and thinking of going out in the bay. How does your boat handle it? Do you take into the ocean?
Thanks!
As long as you go out early and get in by noon or so it's like glass! Literally the smoothest water you'll ever be in. Look at the water in that shark pic, it's totally flat. That was at around 11:30 today. You just have to be careful when the wind comes up because it can turn to whitecaps in a matter of minutes. These boats do amazingly well though, as seen by all the guys that have made the Bimini trip. I'm not taking my little 21 footer out to the Faralons, but we've gone under and a little bit past the GG bridge and it was fine. The south end of the Bay is always smoother though, way smoother than up by the GG or Bay Bridge.
 
That is one cool looking creature.
I love what you did with the dash. I may be following your lead.

I urge, beg, insist, demand, and pout until you comply with a full detailed write up of how you got these things quieter. Remember you are dealing with mere mortals so please dumb it down. It would be helpful if you could point us to the exact muffler you used. We Yamaha owners really need your help with this.
 
Some people would say you have done too much to your yammie and that its not really a yammie anymore...


Screenshot_20180208-193500.png i say it looks great!!!
 
I am convinced I need to do the mods @gmtech16450yz has done to quite things down. I have a super hard time with backgroud noise. Hopefully they come out as good. So muffler wrap will be first in my list. My question is will removing the reaonators make things better or worse?
 
Wait, how did I miss all your mods? Link us in the right direction man!
 
So did you add those moroso mufflers in line, or did they replace the waterboxes?
 
I'd like to see the mod where he got all that stuff to fit in his dash.
 
How do u think the muffler mod would work on the mr1 turning 10k rpm?
Good question! I am sure one of us MR-1 owners will do something very similar as soon as I can get into the boat when it warms up. I really need to quiet the ride some.
 
I don’t recognize the helm controls and gages. @gmtech16450yz you keep these mods up and we will have to send you to thehulltruth so you can mingle with outboard crowd. Impressive stuff!
 
I urge, beg, insist, demand, and pout until you comply with a full detailed write up of how you got these things quieter. Remember you are dealing with mere mortals so please dumb it down. It would be helpful if you could point us to the exact muffler you used. We Yamaha owners really need your help with this.
@gmtech16450yz PLEEESAE. What he said.
Seriously. Please.

Especially this part:
It would be helpful if you could point us to the exact muffler you used.

--
 
@gmtech16450yz PLEEESAE. What he said.
Seriously. Please.

Especially this part:
It would be helpful if you could point us to the exact muffler you used.

--
I googled itand it's a glasspack shaped muffler but a spiral inside and they offee in a few different diameters and in stainless. About $107 each it appears.
Waiting for him to chime in but i think it may be wrapped as well with insulation.
 
Yep. The other details are in a couple of posts including this:
The throttle/shifter Yamaha SHOULD have put on our boats...

^^^^^ pics of my insulated water boxes in that link. In the last pics you can see the foam mattress insulation I put on the front panel of the rear cleanout compartment.


Also, hints from a tightwad...

Find and buy a cheap memory foam mattress from like Ikea or someplace. A twin sized mattress will give you enough foam to insulate a lot of one of these boats and will be way cheaper than buying the same stuff as "sound insulating" foam.

Buy, or secretly use your wife's electric knife to cut the foam with. (lol) Electric knives work great for slicing up foam, even making thinner pieces from thick sheets.

Buy some good quality spray adhesive (3m 90 or 77) to attach the foam, spray both the foam and the panel you're putting it on and let it set up for a couple minutes before putting the piece in place.

Take panels like the fuel tank compartment lid off and cover the entire underside of the panel with a layer of foam. Put layers of foam in the rear cleanout compartment, but I'd try to keep them above potential water levels even with closed cell foam. Put chunks of foam in the corners to absorb bouncing sound waves. Think of the foam as sound sponges, they will stop the sound from bouncing around and propagating.

Use (a cheap version) of dynamat to stop panel vibrations only. Dynamat is more of a vibration canceling approach, it's not going to "absorb" the sound like foam will. Two different solutions for two different situations. Sometimes I'll use dynamat on the actual panel, and foam on top of the dynamat. Absorb the sound waves and dampen the vibrations at the same time. It's really an interesting science, read up on what works best in each particular situation and you'll have better success with less time and money spent.

Marvin- The water boxes don't get super hot since they have water going through the exhaust too. They do get warm though, and I'd be careful using anything that will melt on them. That's why I used fiberglass insulation and aluminum tape on mine. The fiberglass may be a little overkill as far as it's ability to take higher heats, but at least I don't have to worry if they do get hot. It also meant I could make the layers pretty thin. It doesn't take much to cancel the "tinny" sound of an aluminum can muffler as long as the layers are tightly wrapped to the can. The thickness of the insulating layer I put on my water boxes is no more than 1/2 or maybe 3/4 of an inch thick.

All those mods help, but the muffler I think is special.

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@gmtech16450yz I am looking at all your pics. of the muffler install, exhaust hose routing. One question...if I am looking at them correctly, did you swap sides that your exhaust exits at stern in order to accommodate the longer runs or not. Hard to see routing and if you were able to exit on the same side as original. I know it all custom to the outlet, and I have a different boat/year anyway, just wondering as I wait for spring mods to begin.
 
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