Exhaust Noise

Bigearl · Post by **Bigearl** » Tue Sep 18, 2012 6:10 pm

I have just discovered this site and and found some very interesting posts and issues similar to mine. I own a 1977 F28 which I bought in 2000 when I retired as I planned to cruise from Lake Ontario and through the Trent- Severn canal system to Georgian Bay and on Georgian Bay.
Just as well I was retired as a spent a good deal of time sorting out bad work by a previous owner, mainly electrical. Motors are Chrysler 318s with Paragon V drives.
My wife and I have done several enjoyable cruises and have just completed a cruise from Mattawa on the upper Ottawa River through the Rideau canal to Kingston on Lake Ontario, about 250nm. This is a great boat for the canals as it is so very maneuverable and the walk around deck makes it easy to get to the bow during locking through etc.
I fixed a bad distributor (rusted and broken springs on the mechanical advance) and then had to reprop as I only had 21kts at 4400 rpm on both motors. After putting on 14x11 props I was able to get 29kts on GPS at 3900 rpm. I find a cruising speed of about 17 to 18 kts at 2600 RPM is a good speed for on plane running.
As for exhaust noise I find it very noisy from about 1200 rpm to 1700 rpm particularly when the motors are in sync.
Does anyone else have this issue?
I am thinking of extending the exhausts with rubber elbows into the water which will quiet it, (I hope), until it comes up on plane. At higher rpm I don't find the noise objectionable.

prowlersfish · Post by **prowlersfish** » Tue Sep 18, 2012 6:55 pm

Your mufflers could be burnt out inside .

pnmudge · Post by **pnmudge** » Tue Sep 18, 2012 10:43 pm

Bigearl wrote: I find a cruising speed of about 17 to 18 kts at 2600 RPM is a good speed for on plane running.

Wow! you get 17 - 18kts at 2600??? That's incredible! Planing, we get about 14kts at 2800 - 3000 RPM..... and cruise 7.5 kts at 1500rpm most of the time, not on plane.
We have 14 x 10 props, which were super-cupped when we bought them, but we've since taken all cupping out.

Can I ask what you burn at your planing speed?
We do 15lt/hr at 1500, and about 50lt/hr at 3000

Sorry, can't help you with the exhaust noise....

~DarkNemesis~ · Post by **~DarkNemesis~** » Tue Sep 18, 2012 11:14 pm

prowlersfish wrote:Your mufflers could be burnt out inside .

+1 mine were

aaronbocknek · Post by **aaronbocknek** » Wed Sep 19, 2012 2:18 am

~DarkNemesis~ wrote:
prowlersfish wrote:Your mufflers could be burnt out inside .
+1 mine were

yep. probably the mufflers.

k9th · Post by **k9th** » Wed Sep 19, 2012 6:11 am

Welcome aboard and you have a beautiful area to go boating in. I've been in that area a couple times and can't wait to get back.

larryeddington · Post by **larryeddington** » Wed Sep 19, 2012 10:33 am

Probably the old rubber mark II mufflers are burned out, and they are not longer available. I got two 4 inch mini mufflers for mine. Have not plumbed it as yet and do not know how loud it will be. Space is a problem at aft side of engines for plumbing mufflers.

Bigearl · Post by **Bigearl** » Wed Sep 19, 2012 10:34 am

Thanks to all who responded to my post re exhaust noise and the welcome, boaters are generally such great folks and Trojan boaters even more so. I guess as a first step I should replace the mufflers and see what that does, my wife says we sound like a train when we run at 1500 rpm.
To pnmudge I had Bayview Propeller do the calcs for me and that is what I went with, 14X11 cupped props, they claimed this was what the boat originally was supplied with. I keep a deck log and record all fuel purchases and miles run by GPS and work this back to gallons or liters per nm, as a result all my fuel consumption data is a mix of on and off plane cruising. My average is 3.6 liters per nm (0.95US gallons/nm). When I do have an opportunity to run at 17-18 kts for longer periods I seem to get about the same fuel consumption as at 8kts which is about as fast as practical without getting up on plane. That works out to 16 to 17 gallons per hour.
I know my port motor is not as responsive as the starboard motor and I believe this in part is due to the distributor which does not give as smooth an advance as the stbd. one. With a timing light I can see the timing bounces around too much, if I correct that I might get a slight improvement in fuel consumption.
Hope that helps.
Bigearl

larryeddington · Post by **larryeddington** » Thu Sep 20, 2012 8:56 am

When hyou get the muffelers installed, we would like to see pics as my f28 is very difficult to exhaust plumb. Going to se one 4 inch muffler per engine, thought about crossing engine exhaust from one side to the other using long mufflers bolted in paralell to transome.

aaronbocknek · Post by **aaronbocknek** » Thu Sep 20, 2012 1:17 pm

would something from centek work for your boat? will a 'lift' type muffler work in a tight location?
just tossing out ideas.
aaron

http://www.centekindustries.com/product ... tions.html

Bigearl · Post by **Bigearl** » Thu Sep 20, 2012 9:50 pm

Thanks for the suggestion, I checked the Centex website and I am concerned that the lift type mufflers would result in too many elbows etc. As Larry says plumbing the F28 is difficult particularly as there is limited room for length although diameter is not an issue. My boat is now stored for the year on the hard about 200 miles from my home. (This is as I broke my cruise into 2 parts, I will pick up again next year and return via a different route). I am still considering making exhaust extensions into the water as this reduces both noise and fumes at low speed (before going on plane). I wonder if Larry can tell me the outside diameter of both the exhaust flange and pipe at the outside of the transom of the F28? I am thinking of moulding two fibreglass extensions similar to the way the Fresh Air Exhausts do it. I have seen reports of this and the results seem good.
Bigearl

larryeddington · Post by **larryeddington** » Fri Sep 21, 2012 10:24 am

Yep I can tell you as soon as I get the measurements. Both have a modest turn down of the tips. BTW the tips are not available. I will get back with all the measurements. Definitely 4 inch diameter from engines, the transome hole is as I remember 6 inch and could not fine anythine unless custom made.

Again I will take a picture of the through the transome out of the boat and give size.

Bigearl · Post by **Bigearl** » Fri Sep 21, 2012 1:29 pm

Thanks Larry, I did see various sizes of thru transom exhaust pipes from Overtons. I don't plan to replace mine, just plan to put a flange against the existing flange with a pipe big enough to go over the existing down turned existing pipe.
Bigearl

larryeddington · Post by **larryeddington** » Wed Sep 26, 2012 12:47 pm

Here some pics of my exhaust tips for my F28, hope they help.

MattSC · Post by **MattSC** » Wed Sep 26, 2012 9:28 pm

I have a pair of Centek Mini-Max 4" on my F-26. From the specs they were designed for v-drives or tight installations. They sound good, but I believe they make quieter ones than this. It's noise rating is fair, but does sound just as good as my Camaro...

http://www.centekindustries.com/minimax.html

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