I have a 84 model 39' Marinette cabin cruiser that is my weekend home and my baby It still has it's original twin 440 chryslers installed and they run beautifully with 700 hours on the clocks, and make this girl get up and go to the tune of 38 mph. I have as of 4-5 years ago give up racing and most all of my expensive vices except for the boat and it is my full time summer hobby.

I am wanting to play with a fresh set of motors and am thinking of buying a set of older motor home take out engines to start the builds from but have a couple of questions to start with. I have studied here and made myself aware of the high mount water pump deal, I do not want these I know.

I am interested if the heads and blocks varied from year to year in the 1974 to 1978 time frame in these types of applications ??

I understand that my boat engines were very similar to the Chrysler industrial engines used in ground power units and maybe some other industrial equipment like air compressors. Do any of you have or know where to find a close proximity of a dyno sheet so I can start out with an understanding of the torque curve of these engines. For my application I need all torque and 4400 ish rpm redline. Te original engines are rated by what ever means at 330 hp. but I have never known the torque. They tend to out run the 454 chevys that were put into these same boats the next year by about 1 to 2 mph if that is of any value to know.

Since one of the engines is a reverse rotation AI have to choose between building one as this configuration or switching to both std. rotation.

These will be mild smooth idle and want the max torque I can make in the 2200 rpm to 3000 rpm range type of builds, as I spend most of my time running in that range.

In the end I am running wide open in the 3800 to 4000 rpm range now due to being over propped I assume. I want to be able to pull this same prop size at 4400 when I am done, if all goes swimmingly so to speak.

Is there any advice on the motor home engines as cores and does anyone know about the torque #'s my original engines might of made.

I mainly want to build engines before I need engines and not loose a season of boating. I will be moving all of the boat marinization specific stuff over to the new motors and pickeling the old engines in case I need them in the future. I have talked to 440 boat guys in the past and have been warned that since these are fresh lake and river water cooled that my original engines will be rusted terribly inside to the point that the motor home cores are the far better starting point for heads and blocks.

For what it is worth I am thinking of using re-worked original steel heads and buying some 500 to 50? ci. stroker kits from 440 source or where ever this post may lead me for these builds.

I'd be happy to listen to any other comments as well.

 

If those are Industrial block... Thats what i would try to stay with... That way everything stays a direct swap.... No Guessing....

I also think I would do the overhaul in the off season... Give you time to really clean up the engine bay.

I dont see it taking to long for a rebuild, unless the block and heads are junk and to thin. That might give you a problem?

Careful on the upping the Torque to much... That has been know to rip the engine haul mounts loose.... Just food for thought....

I would love to see this tread with photos and all you do to this.... Very Cool.

I know.... This was no help to your answer.... Sorry.... Just my 2 cents.

 

I would keep the same setup with one a reverse rotation. Would probably make the boat smoother running..
A special needs cam ? I would call Comp cams and talk to them.. Contact Hughes Engines they may possibility even have a used Ind block

 

I have talked to a guy that has done a couple of boats with the twin engines running the same direction and he experienced no adverse effect from it. This id an all aluminum boat so the engine beds and stringers are all aluminum so will have no issue with making more torque. I will do the swap in fall or early spring but will keep my old long blocks in tact for back up engines.

The one other criteria that has to stay is the 700 to 800 rpm max idle to protect the transmissions. I am thinking along the line of just doing a couple new 500+ long blocks and maybe even moving my cams and and accessories and preformer intakes over to them, maybe check to see if a bit higher ratio rocker assemblies are available to drop in place. I am just wanting a 1 for 1 torque increase for the extra cubic inches. The water cooled exhaust is the most difficult to over come with only a couple of expensive options available.

 

Also Check with old man Banks... He might still have a few Industrial blocks laying around?

Gale Banks---- 1-800-601-8072
Or
A&A Midwest for a couple cores
1-800-826-7403

 

I was really hoping someone on here had some concept of what a torque graph might look like on these OEM 330 horse power marine/industrial engines. ?? Please !!!!

 

I think I finally found my answer, I think these engines are of the 330 horse 460 torque variety.

 

For a Marine application I would stick with the stock rocker arms or spring for the MP HD rockers

 

Some RPM's listed here: http://www.lhmopars.com/engines.htm

 

I would also find the designed hull speed before I went to far trying to overpower the hull drag.

And with keeping the opposite rotation props you can walk the boat sideways while docking.

 

There are lite weight all aluminum cruisers with planing hulls, more power goes faster, 20 mph at 2100 rpm and still giving 36 mph at 4000 rpm so diminishing returns are coming into play but plenty of room to go faster with an extra 100 ft. lbs. per. engine of torque allowing it to turn 4400 or 4500 rpm. I can't say personally but have talked personally with at least one fella on this forum that has done the twin std. rotation engines on more than one boat with no adverse effects or so negligible it don't mater so that is still up in the air. If I end up buying some good marine take outs then I might possibly reuse the cam arrangements with 1.6 rocker assy's for a slight bump in lift and duration and just rely on cubic inches and heads for the additional power. Here is a couple of pictures of it under power running 35 ish. I'd say. Were not talking displacement hulls here.

 

nice boat!

 

Your 74-78 motors will all be fine NO weird cooling hookups. Maybe an ign kill for shifting ?? Run some water pump lube rust inhibitor through them when parked...