Muffler/Exhaust - Freedom 39

Engines, Drive trains, Propellers, Steering, Ground Tackle and other mechanical system
User avatar
THATBOATGUY
Posts: 574
Joined: Thu Dec 04, 2008 9:50 am
Location: F40 CC CK Maryland
Contact:

Re: Muffler/Exhaust - Freedom 39

Post by THATBOATGUY »

The aqualift should take your cooling water as high as possible as soon as possible (within reason obviously) with the rest of the run downhill. In the U.S. Exhaust hose is sold by I.D. Our 2 inch exhaust hose on Marquesa is 2 inch ID. The exhaust elbow is approximately 2 inch O.D.

George
George and Kerri Huffman S/V Marquesa Freedom 40 CC CK Sail MarquesaImage

Mike Holibar
Posts: 174
Joined: Mon Jun 01, 2009 12:41 am

Re: Muffler/Exhaust - Freedom 39

Post by Mike Holibar »

Hi Dean,
I had a look at Fyne Spirit's exhaust system over the weekend. She has a waterlock p60 muffler sited in the bilge just aft of the gear box to starboard of the shaft. P60 in think refers to 60mm id of the muffler, The Hoseis all 3" id while the thru hull 2.5"id. I took some pics but haven't worked out how to load them on this site. If you send me your email I should be able to send them to you directly.

Cheers,
Mike Holibar
S/V Fyne Spirit of Plymouth (Freedom 39PHS-1989)
Lyttelton
New Zealand

User avatar
OldRover
Posts: 60
Joined: Tue Feb 08, 2011 6:25 pm
Location: New York, NY

Re: Muffler/Exhaust - Freedom 39

Post by OldRover »

Mike, thanks for the assistance. Sounds like you have what I would think is correct for a 50hp diesel. Looks like I will be pulling some undersized hose... At least I haven't purchased waterlock yet. I look forward to the pics. Sounds like I was looking at the right spot for placement. I was looking at the Vetus nlp75, but its going to be real tight. Your pics will be a great help. I'll PM my address.
'82 F39 ph

User avatar
THATBOATGUY
Posts: 574
Joined: Thu Dec 04, 2008 9:50 am
Location: F40 CC CK Maryland
Contact:

Re: Muffler/Exhaust - Freedom 39

Post by THATBOATGUY »

This is a good thread,

Mike, I'm very interested in any specs you might have for back pressure for the 4-108. I'm rebuilding one for Marquesa this spring and if it needs upgrading the exhaust system then it will get it at that time. No use going to all the trouble if it's just going to have to work harder than it needs to.

George
George and Kerri Huffman S/V Marquesa Freedom 40 CC CK Sail MarquesaImage

Mike Holibar
Posts: 174
Joined: Mon Jun 01, 2009 12:41 am

Re: Muffler/Exhaust - Freedom 39

Post by Mike Holibar »

Hi George,
I have been trying to get some more specific data for the 4.108 from my Perkins contacts without much success as it is some years since these were sold. Still, I hope to have something in the way of a general guide in the next day or two. I did speak to an Auckland contact, Jim Kilmartin who was Perkins sales manager around the time these engines were being sold. As luck would have it he currently owns a Gary Mull designed 39 footer "Floyd" powered by a 4.108. Floyd was built in the States and had the 2" exhaust system. When Jim got her he was concerned that his engine would not reach full rpm and intitially thought this was down to prop size, which is the first thing that I would have thought of. However, nothing he did to the prop would make any improvement. Eventually he noticed the undersize exhaust, and, suspecting this may be the cause changed all the exhaust to 2 3/4"-3" (he is not sure of the exact size) except for the through hull which was left at 2" bore. The result allowed the engine to achieve full rated rpm, an increase of about 300rpm. The Perkins service manual for my engine notes other faults caused by excessive back pressure other than loss of power. They include over heating, excess fuel consumption and smoking, but these were not apparent in Jim's case.
Regards,
Mike Holibar
S/V Fyne Spirit of Plymouth (Freedom 39PHS-1989)
Lyttelton
New Zealand

User avatar
THATBOATGUY
Posts: 574
Joined: Thu Dec 04, 2008 9:50 am
Location: F40 CC CK Maryland
Contact:

Re: Muffler/Exhaust - Freedom 39

Post by THATBOATGUY »

More interesting yet. Did your friend change mixing elbows also or shim up to the larger hose? I'm determined to do everything I can for the rebuilt engine as we will relay on her for another year or two of cruising before putting the boat on the market.

I'll take facts and figures over "this is the way I've always seen it" any day. Thanks for digging.


George
George and Kerri Huffman S/V Marquesa Freedom 40 CC CK Sail MarquesaImage

Mike Holibar
Posts: 174
Joined: Mon Jun 01, 2009 12:41 am

Re: Muffler/Exhaust - Freedom 39

Post by Mike Holibar »

Cheers George,

I got hold of Neil Blue today, he is the national technical manager for Perkins, Detroit, MTU engines. He tells me he no longer has data on 4108 exhausts but in terms of recent and current Perkins Sabre marine engines the maximum allowable back pressure is 3"Hg, or 10 Kpa or 1.5psi. This applies to all the engines. The pressure is usually measured just after the mixing elbow. The way to step up the size from the mixing elbow is to weld a cone between a short piece of 2" ss tube (same od as the mixing elbow) and what ever id hose you are stepping up to. The cone should be available at any ss tube supplier. Such an adaptor would usually be about 6 inches long, and you just use a short piece of exhaust hose to join it to the mixing elbow. It would seem the waterlock muffler type p60 fitted on Fyne Spirit has 60 mm id and I would guess about 75 mm (3") od. So 3" hose would be the size to go for, while ids for gooseneck and though hull are likely to be about 60mm - they wouldn't want to be any less than this. The mixing elbow is a standard item and is fine at 2". At this point the elbow is mixing hot gas travelling at high velocity with water. The gas needs room to expand and slow down hence the need for larger hose. It's a bit like friction, the smaller and longer the hose, the higher velocity it must travel at and the more pressure required to drive it through the system. Even though certain parts of the system, like the muffler,step down in diameter, it is only briefly, the gas travelling through the system mostly in the larger hose at lower speeds and pressures. Fyne Siprit doesnt have a goose neck as such, and I think the id of the thru hull is greater than 60mm. As I have been thinking on this subject I think I would be going for a larger goose neck than 60mm id and perhaps step up both that and the thru hull to 3 inch id, just to be on the safe side.

Regards,
Mike Holibar
S/V Fyne Spirit of Plymouth (Freedom 39PHS-1989)
Lyttelton
New Zealand

User avatar
folotp
Posts: 54
Joined: Mon Aug 08, 2011 10:52 pm
Location: Lake Ontario, Canada
Contact:

Re: Muffler/Exhaust - Freedom 39

Post by folotp »

Hi all,

Thought I would revive this thread! I too have the 2" ID exhaust hose and muffler with a Perkins 4.108 on my F39PH and plan on replacing the exhaust hose this winter so would be interested in any real life experiences. Were there any conclusions on the proper size exhaust for the F39? Has anybody upgraded to 3"?

OldRover: Did you manage to fit the Vetus NLP75 (3") Waterlock Muffler somewhere? I'm thinking of going up to 3" as well, but the space in the bilge for a larger muffler is quite limited.

Also, I'm thinking of installing the Vetus Gooseneck/Muffler NLPG75 (3"). Does anyone have experience with this product?

Thanks.

PA
Pierre-André Folot
s/v “Farfelu” - Freedom 39 PH 1983, hull #14
Sailing the Thousand Islands and Lake Ontario
Canada

User avatar
OldRover
Posts: 60
Joined: Tue Feb 08, 2011 6:25 pm
Location: New York, NY

Re: Muffler/Exhaust - Freedom 39

Post by OldRover »

I wound up going with 2 inch inside diameter wired hose. This was primarily due to routing issue with larger exhaust hose (passing through to the aft compartment and bending a gooseneck below the cockpit. I kept the length to a minimum with minimal bends (only a small bend at the outlet). A larger hose would breath better, but the 2 inch is an acceptable minimum. The smaller diameter also aids in low end torque which is good for me since I tend to not run at wot for extended periods.
I was going to install a Vetus NLP waterlock. Fit is a little tight, but definitely can work. But I got a good deal on a Vetus NLPH50. This unit is real easy to place since it runs inline with the hose and is only about 5 inches in diameter. This unit really turned out great. It adds some sound reduction and preforms well not really adding backpressure. I looked into the NLPG too. Vetus recommends this as an additional muffler (primarily for sound reduction and should be used along with a waterlock). I did happen to see such a setup and it does make things quiet. It also should make the installation take up less space and tuck nicely up into the hollow of the transom. I decided not to include mainly due to added expense. I would not use it without a waterlock since there is a risk of sucking water laying in the exhaust hose back into the motor on startup.
'82 F39 ph

Post Reply