Turbocharging a Marine Engine
 

There are two speed marine transmissions that should all you to build RPM's
quickly at slow speeds and still give you a good top end.

"Paul" wrote in message
able.rogers.com...
I think the "dog coming out of the hole" comment was based on putting a
bigger prop on it to take advantage of the increased top end. But without
that power down low then the it would be overpropped until the turbo
kicked
in.

wrote in message
...
Hemicuda wrote:
: So from what I can summarize from the above posts are that the turbo
: will probably work great while cruising and at top end but will be a
: dog coming out of the hole. This is a dumb question but I thought

It wouldn't be a "dog coming out of the hole". It'd act mostlyl like a
naturally aspirated engine.

Turbocharging a Marine Engine
 

Most boats have to achieve about 2800 rpms to plane off and start moving.
Low hp will still produce this rpm but the time to do it will increase as
you lower the power. Right now you produce a certain amount of power that
allows you to turn a certain prop to 2800 rpms within a certain time. To
maintain 5000 rpms at top end with more power you will need a larger prop.
The catch is you are not producing more power at low rpms so you increase
the time required to achieve 2800 rpms.

Think of it this way. An engine without a turbo in a car will achieve a
zero to 30 mph time of say 3 seconds and a zero to 60 time in 5 seconds.
The same car with a turbo will achieve a zero to 30 mph time of 3 seconds
and a zero to 60 time of 4 seconds (boost kicks in from 30 mph up). Now if
you reduce the gear to keep rpms under redline you just increase the 0 to 30
time to 4 seconds. Just an example.

Given the hole shot problem, heat generated, and trouble to implement hosing
and stuff - I would recommend going ahead and doing the blower. Blower may
use some more fuel but since your cruising with a lower throttle setting,
you should not see much of a change.


Tony
My boats and autos - http://t.thomas.home.mchsi.com



"Hemicuda" wrote in message
om...
So from what I can summarize from the above posts are that the turbo
will probably work great while cruising and at top end but will be a
dog coming out of the hole. This is a dumb question but I thought
that at slower speeds boats require less horsepower to move them
through the water. As the speed increases so does the power
requirement for a certain hull design. Is this true? If so it
appears that the low end lack of boost shouldn't kill me. Or am I
totally of base? The other thing I was thinking of was to put smaller
turbos on the engine to reduce lag but sacrifice top end boost.
Marine engines rarely go over 5,000 RPM so I could probably go with a
smallish turbine housing with a waste gate that will bring on boost
quickly and then dump the excess exhaust gas at higher speeds. I know
the heat will be a problem but I think that is manageable but I don't
want to take forever to get up on plane. Has anyone seen or ridden in
a gasoline turbo'd boat and seen how bad the hole shot was? The
reason I want to stay away from a blower is that although it will
boost power I think it will hurt the fuel efficiency. Also blowers
tend to be expensive and I can score a pair of T3 Turbos from old T
birds which would fit a 5.0 or 5.7L fairly well for cheap at a junk
yard and fabricate a set-up. Thanks for all the help and I
appreciate any more thoughts or info you could pass on!

Turbocharging a Marine Engine
 

Turbocharging a Marine Engine
 

"Rick & Linda Bernard" wrote in message ...
There are two speed marine transmissions that should all you to build RPM's
quickly at slow speeds and still give you a good top end.

I'm betting this guy does not have extra space between his 5.7 and
outdrive for a transmission :-)


"Paul" wrote in message
able.rogers.com...
I think the "dog coming out of the hole" comment was based on putting a
bigger prop on it to take advantage of the increased top end. But without
that power down low then the it would be overpropped until the turbo
kicked
in.

wrote in message
...
Hemicuda wrote:
: So from what I can summarize from the above posts are that the turbo
: will probably work great while cruising and at top end but will be a
: dog coming out of the hole. This is a dumb question but I thought

It wouldn't be a "dog coming out of the hole". It'd act mostlyl like a
naturally aspirated engine.

Turbocharging a Marine Engine
 

Turbos work well in marine applications, one of the side benefits is that they
also make great mufflers. Here is a good thread on a marine turbo project:

http://forums.hotboat.net/ubb/ultima...c;f=3;t=000483

Turbocharging a Marine Engine
 

Thanks for all the comments. A marine trans is not an option so if it
comes to that I will definitely go a different route. I am not
looking for absolute power in this set up but instead looking fora
viable alternative to shoving a 502 in an express cruiser. My main
goals for the project would be improve performance of a small block
without the disadvantages of big block. As to the issue of fabbing a
set-up I should be able to get all the fittings I will need and mig
them all together. The cooling issue does concern me because I don't
want to build jacketed headers but I was thinking about possibly
tracing them tubing that water is pumped through and then rapping the
piping. As long as I have enough flow through the tubing the water
should stay liquid and cool the system. Since I am looking at putting
this system on a 5,000# boat loss of accelaeration will be a big deal
because I would still like to have the functionality to use it for
water sports. I understand some of the reasoning about the
acceleration problems. Is there any slippage of the prop in the water
during acceleration. If I can get it to about 1000-1500 rpms and put
some small turbine housings on the turbos I should be into boost by
this point. The small housings will kill my top end but that
shouldn't be a problem seeing as the engine probably won't see more
than 4500 RPM. Are there any technical articles on the start-up
torque and HP requirements of boats that I could read? Thanks for the
help.


572 wrote in message . ..
Turbos work well in marine applications, one of the side benefits is that they
also make great mufflers. Here is a good thread on a marine turbo project:

http://forums.hotboat.net/ubb/ultima...c;f=3;t=000483

Turbocharging a Marine Engine
 

"Hemicuda" wrote in message
om...
Thanks for all the comments. A marine trans is not an option so if it
comes to that I will definitely go a different route. I am not
looking for absolute power in this set up but instead looking fora
viable alternative to shoving a 502 in an express cruiser. My main
goals for the project would be improve performance of a small block
without the disadvantages of big block. As to the issue of fabbing a
set-up I should be able to get all the fittings I will need and mig
them all together. The cooling issue does concern me because I don't
want to build jacketed headers but I was thinking about possibly
tracing them tubing that water is pumped through and then rapping the
piping. As long as I have enough flow through the tubing the water
should stay liquid and cool the system. Since I am looking at putting
this system on a 5,000# boat loss of accelaeration will be a big deal
because I would still like to have the functionality to use it for
water sports. I understand some of the reasoning about the
acceleration problems. Is there any slippage of the prop in the water
during acceleration. If I can get it to about 1000-1500 rpms and put
some small turbine housings on the turbos I should be into boost by
this point. The small housings will kill my top end but that
shouldn't be a problem seeing as the engine probably won't see more
than 4500 RPM. Are there any technical articles on the start-up
torque and HP requirements of boats that I could read? Thanks for the
help.


572 wrote in message
. ..
Turbos work well in marine applications, one of the side benefits is
that they
also make great mufflers. Here is a good thread on a marine turbo
project:

http://forums.hotboat.net/ubb/ultima...c;f=3;t=000483

Perhaps something like this:
http://www.amazon.com/exec/obidos/tg...glance&s=books

Mark Browne

Turbocharging a Marine Engine
 

I already have Hugh McInnes book which is really solid on the
fundamentals of Turbo'd engines. Does Bell's really add that much?
The guys at the JYturbo forum speak higher of McInnes book. I am
looking for a little more on the hydro-dynamics of props during the
acceleration of a boat. I am familiar with pumps (my back ground is
an engineer) but I not that familiar with the specifics as they apply
to boats. I want to get some rules of thumb about how much torque and
HP are needed during boat launch so that I can make some guesses about
whether a turbo would work in the application I'm looking at. Do you
know any books concerning that subject? Thanks for the help.

Perhaps something like this:
http://www.amazon.com/exec/obidos/tg...glance&s=books

Mark Browne