Re-power with underwater exhaust

fl amberjack

fl amberjack

New Member
Jun 24, 2015
27
ft lauderdale
Boat Info
amberjack 34
Engines
8.1 mercs
I am repowering my 2001 amberjack 34 with 8.2 mer Mag DCT HO 425 HP and am wondering if anyone here has done a re-power converting the old exhaust with mufflers over to underwater exhaust? I will need a relief port at idle for sure...It seems like it should work fine, keep the noise and fumes way down but wondering if there are any issues to consider when doing this....any advice or comments would be greatly appreciated :)
 
Everything is possible if you have enough Money!

Seriously, this may be more expensive than it appears on the surface........ new mufflers, new exhaust hoses, bronze under water outlets, plus quite a bit of fiberglass and gelcoat work and bottom painting. None of it is technically challenging for a competent boat yard. The conversion will take some planning because there is nothing to copy as this was never an option for the 330EC or 340AJ from the factory.

I delivered a gasoline powered 340AJ for the local dealer to their other store some time ago, and listening to 2 big block V-8's at cruise speed in a short open boat for 3 hours made that the longest 40 mile trip I ever took in a boat, so this might be a very worthwhile project and one worth going the extra mile for considering the fact that you are investing in a re-power.
 
Well, I guess that is true but when I looked at newer models and hulls like tiara I still would end up with a 10 year old hull and engines for a lot more money. I really like this hull so having brand new fresh fast power over a 10yr old tiara seems well worth it. Yes these 7.4"s are pretty loud and smoky and I really only get 20mph at like 35gph, yikes! I'm thinking I will get 25kts around 30gph with the new setup...really appreciate your input as this is a huge project! PS I will be using all the old hoses and mufflers and can get the bronze exhausts for under a grand. glass work will be an ouchy for sure
 
Don't misunderstand my comment. The 33EC/34AJ and the 37EC are some of my favorite Sea Rays. A number of folks in our area have repowered gas boats with diesels just because they love the boats and con't find anything they like better.

You might want to rethink the idea of reusing the old exhaust hoses and mufflers. With under water outlets, you still have to have an over flow pipe at the top that exhausts out the side of the boat as well as a separate outlet for the under water fitting. Also, just going by the size of the exhaust in the corners of your transom and the online parts lists for the 34AJ (which does not have underwater outlets) and the 34DA (which does have underwater exhausts) I suspect your present muffler outlet is much larger than you will need for the under water fittings. You will need 2 4" inlets, one 2.5" outlet and one 5" outlet and you only have 2 4" inlets and one 6" outlet which it too large for t he underwater fitting.
 
An interesting idea for sure. I know with mine, installing in-line stainless mufflers just before the vernalift cans provided some welcome softening of the exhaust tone.

The typical placement of the bronze exhausts are outboard and towards the stern. On our 340 Amberjack boats the engines are mid-ships and the two exhaust hoses/engine are routed to the outboard sides of the engine room to a vernalift can, then a larger single exhaust tube follows along the side of the hull to the stern corner thru-hull exhaust. Behind the engines are the fuel tanks (which stretch the beam of the boat) and behind the fuel tanks is another bilge area. The bronze exhausts would probably not fit in the engine room floor behind the engines since that's where the prop shaft exits the hull so they would probably have to go in the aft bilge.

I suppose you could provide a diversion fitting for the single large exhaust hose passing through the aft bilge and feed it to the bronze exhaust, but not sure if the hose would be the right size for the bronze exhaust.
 
Last edited:
fwebster said:
Don't misunderstand my comment. The 33EC/34AJ and the 37EC are some of my favorite Sea Rays. A number of folks in our area have repowered gas boats with diesels just because they love the boats and con't find anything they like better.

You might want to rethink the idea of reusing the old exhaust hoses and mufflers. With under water outlets, you still have to have an over flow pipe at the top that exhausts out the side of the boat as well as a separate outlet for the under water fitting. Also, just going by the size of the exhaust in the corners of your transom and the online parts lists for the 34AJ (which does not have underwater outlets) and the 34DA (which does have underwater exhausts) I suspect your present muffler outlet is much larger than you will need for the under water fittings. You will need 2 4" inlets, one 2.5" outlet and one 5" outlet and you only have 2 4" inlets and one 6" outlet which it too large for t he underwater fitting.
Click to expand...


Oh I see...Ok, yes I will have to talk to the guys at the shop about that one for sure....did not realize they were so different, many thanks for the input!
 
Hey Jimmy hope all is well up there :) Yes the plan is to place the bronze ports in the aft bilge...the challenge is going to be getting around the livewell and the fish box as I really need those!! We'll see, engines will be here in about a month so we have some planning time. Working on that hose size issue right now....many thanks and will send pics once its done and speed figures are in :)
 
http://api.viglink.com/api/click?fo...- Page 15&txt=http://www.freshairexhaust.com/ spoke to the owner of fresh air exhaust I think im going this route




fl amberjack said:
I am repowering my 2001 amberjack 34 with 8.2 mer Mag DCT HO 425 HP and am wondering if anyone here has done a re-power converting the old exhaust with mufflers over to underwater exhaust? I will need a relief port at idle for sure...It seems like it should work fine, keep the noise and fumes way down but wondering if there are any issues to consider when doing this....any advice or comments would be greatly appreciated :)
Click to expand...
 

Attachments

  • image002.jpg
    image002.jpg
    20.6 KB · Views: 374
Whoa that looks pretty interesting! Is he pretty confident that back pressure will not be an issue here and will those pipes hanging down effect you cruising performance? many thanks for the picture very interesting....Brian
 
We have a different boat with Crusader 8.1s. The boat was built with transom exhausts. Noise was never a problem, but we did get some station wagon effect when we opened the windshield vent. We are hull 54 and a few hulls later Tiara converted to an under water exhaust that used the same mufflers but added the underwater system. This solved the exhaust problem completely and I had the factory convert my boat. For us it was a good change. Fuel efficiency remained about the same. I'm happy we made the change as we plan on keeping this boat a while.
 
from my understanding the prop wash pulls the exhaust and the pipes are secured to transom or swim platform, this will be a early spring project for me. look at the website there are videos of a inboard boat




fl amberjack said:
Whoa that looks pretty interesting! Is he pretty confident that back pressure will not be an issue here and will those pipes hanging down effect you cruising performance? many thanks for the picture very interesting....Brian
Click to expand...
 
I'd be interested in knowing more since my boat has a custom extended canvas roof which seems to increase the station wagon effect. My concern is how the tubes will fit the corner thru-hull exhaust ports without sticking out too much past the side of the hull. Please keep us updated as to what they can offer and a possible group buy discount??
 
In 1977 Sea Ray built in the underwater exhaust as standard design element.
 
I think this will be more complicated that it may appear.

On the 330EC/340AJ, the exhaust outlets are flared and at the corner of the transom. They are 6" holes so if you are even able to hook the system you are favoring to the outlet, you will have something akin to stove pipes running across the transom and attached to the swim platform.
 
Well I'm still in the Preliminary stages of trying to figure out exactly how these pipes match up to the exhaust outlet he has a plan for this but I have to pull the boat and take measurements inside the exhaust outlet the way he makes it sound the 90° turn is going to be mostly inside that 6 inch outlet so what will be protruding Will not be very much I will do this after I pull the boat for the season in December though he sounds very confident price should be somewhere around 1500 but I'll tell you after doing a three hour run off shore and listening to the drone of that motor I could easily fall asleep out there. X I'll keep ya posted!!


Sent from my iPhone using Tapatalk
 
Nice boat and thanks for the reply...great to hear the underwater exhaust cleaned up the fume problem! I am hoping the emissions on these new mercs are alot less as well
 
[h=2]Re: Re-power with underwater exhaust[/h]
Nice boat and thanks for the reply...great to hear the underwater exhaust cleaned up the fume problem! I am hoping the emissions on these new mercs are alot less as well​
 
You must log in or register to reply here.

Forum statistics

Threads
113,304
Messages
1,430,329
Members
61,165
Latest member
Tjbarone
Back
Top