Fletcher 17 with Jaguar 4.2 6cyl inboard via VP 270 drive,exhaust prob

Hi,first post here,hoping for help and possible ideas.
I bought the boat with 3.8 Jaguar fitted. Proper Barn find project.
I have many pictures for anyone interested.
Boat is mid 60s fibreglass hull
I am using a 1986 4.2 Jaguar engine completely re built, the boat came with a homemade water jacketed exhaust manifold and a pair ( 3 cylinders on each)LANCING MARINE purpose built jacketed
manifolds.
The homemade EM worries me as it’s homemade for a start,the water exit pipe that is connected to a short piece of hose (300mm) long then to exhaust outlet 3” with a flapper externally.
The LANCING MARINE manifolds are well made and completely jacketed, with water injection in the bottom……..these are really want to use.
BUT……
The exit on these manifolds are about an inch back from the oval 3” hose connection, my worry is I am going to get water back into the engine.
I have very little room to the transom,300mm and 600mm respectively.
LM engineer has told me it “ should be fine” to me is not acceptable.
It needs a riser/ dropper but I have very little room.
For general info, I still need to re ply the transom as existing is rotten,the boat will only be used very lightly. More of a historic project than a daily. But I still want it to be RIGHT.
This Jaguar engine was used in lightweight British tanks in the 70/80s and has plenty of tourque,under the guise as CVRT J60 engine, which is the route I am taking, hence the army green intake manifold, and Rolls Royce twin downdraught carb.
Engine is now completely sealed, ancillaries to fit next, hoping to fire up in the next couple of months.
m

 

A few thoughts; I do agree with you about the 3+3 manifold, that is what this engine "wants". But it also depends on the exhaust timing. I guess the tank engine has less valve overlap at top dc than you find in the car. With the 1-5-3-6-2-4 ignition sequence, that would reduce the risk for water blown back as long as you keep the outlets separated all the way. That risk is unacceptably high with the straight collector.

Unfortunately, the water/exhaust mixing zone can't be seen in the pics, could you elaborate on that, please? It may be possible to angle the hose stub down by cutting and rewelding, and then inject the water into the downslope. In the present condition, I'd say that water ingress is less likely while running; problems arise when the engine is killed. The song of this fella with a 3+3 manifold is sheer music, so good luck, it's worth doing right!

 

When sitting at trim, what is the angle of the engine beds? A stern unit I expect based on your reported distances to the transom. For a "historical" project and based on the existing exhaust jacket, I would expect sufficient bed angle to keep the inlet below the exhaust ports and an above water flappered overboarding pipe.

 

Hi,thanks for such a quick and knowledgeable reply,I have marked with small cross within the EM this is the exit point within, and is the same for both EMs.
My thoughts are, to block the exit and drill a pipe fitting barbed to it,then a short hose to an injection point on the downward exhaust hose. Possibly a very short piece of flexi exhaust on the EM oval stub (stainless) then short piece of stainless pipe which is solid with water injection spigot. Then short piece of flexi to transom mounted exhaust outlet, with flapper connected externally. I have included a picture of the current transom configuration as I believe I can go down hill slightly compared with the original set up. I will have 2 outlets side by side with a small gap.
Another huge thought I had, ( and the EM do fit upside down) was to turn the EM over , cool the manifolds, then go dry exhaust piping for a distance, add a mixing elbow at the correct point, and then exit the transom. Lot of work and money, and I lose a lot of engine compartment, and it will get bloody HOT. I’ve also added a picture of the engine compartment so it’s possible to see how cosy this set up is. This was the original 3.8 XK engine in boat when I got it. 1964.

 

Hi
Any thoughts on my ideas,,,,,
I’ve also seen these “ snails” that go with “logs” ( from what I can gather wet exhaust manifolds, that water enters and exits).
I can make my EM into logs,and then add snails to protect back flow of water into exhaust valves.
Do you think this is a viable option?
Thanks
Rob

 

Looking again at another angle, the set up I have with these EMs they actually lean over to the side a long way, also there is a step inside the manifolds before the throat of the exhaust throat passages.
I think I shall push forward and get engine running etc, bench test water flow and temps etc before putting back in boat.
Rob

 

Have you lifted the "lid" and seen what's inside? If yes, any pics?

 

You probably already know this, but from photos of a Phantom 23 that was fitted with similar setup with the 3+3 manifolds, it appears to have a drop (snail) at the ends of the manifolds that then exited the exhaust thru hull to eliminate reversion, with plumbing coming into the top plate as you proposed as well as the snails, and the exhaust outlets in a stacked configuration.

 

Hi
Baeckmo, I haven’t opened,removed lid as they both pressure tested ok. Didn’t want to disturb.
I have taken some close up shots of EM all from different angles. ( I stand corrected they have no steps inside,smooth passages all the way).

SolGato, I have seen this boat/ engine set up before, video of it running on Utube somewhere.
That boat had a lot of input from Lancing Marine, with a very interesting surface drive.
The “ Droppers” you speak of are second generation and unfortunately do not fit my stubs,also they would make the exit from my boat on or just below the waterline. Which I really don’t want.
Because, ( I guess), it was a surface drive the engine was mounted higher in the boat, and it didn’t effect it having the droppers.
I shall attach the EM pics, plenty of time to, resolve exhaust issue, can’t see engine going into boat until at least next year. Got the transom to re do yet.
Although got a nice Bowman oil cooler and Bowman HE F300 from EBay the other week, so all major parts are sourced,just got to get busy.
Rob