Logo
FULL SITE MENU

Tale of Two Lancersepilog

sandkicker

sandkicker

Outstanding Contributor
"Last year I started a thread

"Last year I started a thread

http://www.marineengine.com/discus/messages/12487/214472.shtml

about back pressure issues with 5.7L engines and 280 drives. It's been a busy summer with lousy "work on boat weather" but FINALLY...
This morning I launched the boat with the new thru transom with mufflers setup.

First impressions...At idle the boat has a very nice throaty V8 burble.. at speed, no noisier, possibly quieter than the thru leg setup was...hard to say. But the proof of the pudding was in the running of the boat. It appeared to have markedly better throttle response than before, but most inmportantly... MAX RPMs went to over 4200 from the 3800 I was getting last season. I don't know exactly how high MAX RPMS is as my wife freaks out rapidly as boat speeds get over 35 mph...especially in a mild chop.

I still have some cosmetic/cleanup stuff to do, but I feel that I've made my point...
Don't run 5.7L (or above) V8 exhausts thru the lower unit of a Volvo 200 series drive...take them out thru the transom. Running 5.7L or larger V8s exhausts thru the drive is wasting HP and putting your exhaust valves at risk.

I've had many converstions over the last year with folks and the concensis is that "all those Volvo installs can't be wrong"...

Well... define "wrong". For me, if I have to use a 19P prop to get MAX RPMs running the exhaust thru the leg instead of using a 21P prop.... that's wrong."
 
"Robert,

I'm hearing th

"Robert,

I'm hearing the whirrrr of a hole saw in my future!

Couldnt be too hard to drill those holes and run temporary exhaust hose out the back to test.

Could mufflers be externaly mounted , say under the swim platform?

(don't have much room in my Imperial 230VC stern)

AQ271 with a 290DP drive, 4200 max rpm, typical cruise at 3000 rpm.....

Any Coast Guard requirements?

What size exhaust hose did you go to for the outlets At transom?

John"
 
"Re: Swim platform... Mercruis

"Re: Swim platform... Mercruiser "catalog" shows an "S" pipe for running the exhaust from the elbows to ports "below the swim platform". Maybe that will work for you.

USCG reqs...approved hose for "wet exhaust service".

General Industry guidelines... double clamps on hoses and at least a 1" drip per foot of run.
Should have shutters AND flaps on the ports.
The Merc thru kit comes with both.

I ended up with 3" hose, each side.

Re: hole saw... I used a 3 1/4" saw. I used one of those drill guide thingees to drill a pilot hole thru the transom (mine is very thick). I then reversed the drill bit in the hole saw and used the pilot as a guide to keep square. The 3 1/4 dia saw is actually a bit undersized. Its not undersized for the diameter of the thru hull, but there is a radius in the casting on the point at which the flange meets the barrel of the port. It only took a few mins with a coarse round file (LARGE) to radius the edge. A 3 1/2" drill will result in a hole that is uncomfortably close to the mounting holes for the flange. Be sure to have a squirt bottle full of water and keep the blade very wet, otherwise you can easily burn out one of these blades in less than one hole.

I'll be posting pix on my website in the next few days."
 
"No, did not change the prop!

"No, did not change the prop! Still turning a 15x21. Don't know exactly how many RPMS as the "crew" chickened out totally at 4200 RPMs (which was over 40 MPH) but revs were still climbing. Can't fault her totally, there was a short 1 to 2 ft chop running) Should get boat out tomorrow as I'm scheduled to go fishing with an old friend. Will post RPMs and MPH then."
 
Back
Top