stringer question

[danshat]

I am repowering my 34 DC. The shop stated that if I went to deisel engines it would more than likely require some retrofit of the stringers. The original Chrysler 440's have been removed and the stringers have large grooves in then and on the starboard side have a groove that is cut all the way through leaving an opening at the top of the stringer. Is this normal? I don't believe the 440's were OEM. I think they were added in the early seventies and am wondering what I need to do. I would rather not pay the shop to fix it. I will be on the boat later this week and will take photo's so you know what I mean. I am still in a heated debate with myself between the Cat 3208's and GM 5.7's. Any advice is greatly appreciated.

 

[REBEL]

I would use the existing stringer as a "bed" and then mount an aluminum "C" channel to cap them. Square everything up so its where you KNOW it has to be then pull them off and bed WELL with a bunch of 5200. Bolt them in with some (6?) lag bolts. You want a square, flat plane to work off of for leveling and alignment.
I did just this with an old boat that had wood stringers, took a million measurements and did a dry run on the shop floor. I didnt feel like paying for crane time unless absolutely neccessary.
The figures need to include angles and height for coupling alignment, pipes for exhaust, coolers, hoses etc and MOSTLY, for ease of access for YOU to work on the stuff. While the engine bay is empty, now is the time to clean, remodel and rewire etc. Also youll need to upgrade water intakes, battery cables and controls. Sounds like a fun project. Should be able to knock it out in about 4 days. rebel

 

[REBrueckner]

Make sure you know the mounting dimensions, engine and transmission height and width requirements for whatever engine you select before you install any stringer modifications. You may be able to either widen or narrow the engine bed, if required, and change the height by using an angle iron (inverted L shape) piece.

I don't know the GM's, but the CAT 3208 in moderate HP versions is hard to beat. Try searching here on Sam's ...they have been discussed before.

 

[34Hatt]

Dan I want to see pictures did you look at my repower pictures lots of pictures of the stringers. Would think yours and mine should be very close? Check my rebuild home page link in Signature.

3208 I think will be tight have you thought about Cummins B' series?

 

[Boatsb]

3208 N just fit in a series 1 36. may be too big for the 34.

 

[rtrafford]

As posted above, consider the Cummins B. Also, I recommend sticking with steel, not aluminum for stringer mounting sisters. It's easier to do right without something going wrong, now or later, like metals et al.......

 

[Walter P]

Alum is actually the better way to go. Steel will rust etc. Be sure to use the proper grade of Alum. My first choice would be 7075 T-6, followed by 2024 T-3 of 4 and last by 6061 grade. The 7075 is considered "aircraft grade" and is actually stronger than mild steel. It's main negative is that it is almost impossible to get a good weld on it, but you shouldn't need to weld anything to it for your purpose.

Walt

 

[yachtsmanbill]

OKEEDOKEE!

 

[yachtsmanbill]

POOOEY!!

 

[Walter P]

Hey Bill,

Yes, I know that your's are welded, as are mine, but I don't think it has to be. The new mounting pads can be designed as bolt on's but I guess welding is better in the long run so forget 7075 T-6 and check weldability of 2024 T 351 and if that still doesn't meet specs (I think it will), then go to 6061 which you can weld easily and is still very strong.

Walt P

p.s. I hate show off's posting pictures of their super clean, beautifully painted engines. Makes us common folks look bad.

 

[drburke]

The Cats weigh a lot compared to the Cummins B, which is not too much more than the optional DD 4-53s from the factory, ignoring the torque increase. Maybe that also may be why the shop suggested a stringer upgrade.

http://www.adieselengine.com/new_page_1.htm

For the record, the stringers are hollow and my lag bolts only grabbed the outer shell, which is fine except the previous owner stripped them out and decided not to open up the metal for larger bolts and just epoxied them in. A close look shows I twisted, drilled, or otherwise cut mine out, and need to pour in some epoxy/mat to make an interior structure for new bolts.

Dan, some of us watched closely the EOTL work--attached pics should be familiar (renewing gassers until Cummins install next winter).

DAN

 

[boatwright]

the change from gas to disel and the differance between hp/torc/etc, means the strength of the stringer/hull bond and design need to be evaluated.

 

[31FlyCruzr]

My understanding is that the fill of the stringer is hard dense foam. Can you lag bolt down into that? My engine bed is alumunum C channel bolted thru the stringer sideways with bolts, not lag bolted down into the stringer. Engine mount is bolted down thru the top of the channel.

Bill

 

[Boatsb]

Do not lag into the stringer. The foam was there to form the shape. The cap needs to be through bolted. If you need to increase the size of the cap or replace it because it was cut up do so with good materials.

The stringer and hull are designed to take only so much but the 250 HP engines you are putting in should not give you problems. The ones you took out are more HP and probably close in torque.

 

[Avenger]

I may be misinformed, but I always thought that Hatteras had included a steel plate in the lay up of the top of the stringer in the engine area so that it could be drilled and tapped for engine beds. No???

 

[rtrafford]

not going to argue the point....I simply prefer steel tied to my engines as to not introduce yet another metal in a critical location. personal preference, I suppose... I coat mine well with a primer and paint well prior to and again after installation. No rust.....

 

[danshat]

Here's a couple of pics. There is definately a mounting plate under there but the new engines are a lot smaller. You can also see where the stringer was molded around part of the engine. I will get a picture of the part that really scares me later. Also no foam inside my stringers they're hollow.

 

[34Hatt]

Yes they are hollow and were made on a mold then put in place then had foam shot in. It seams the foam just got dissolved over the years in many spots. Those stringers have 3/4" or more in the top so all of my hardware is tap and then bolted in with some 5200 so it won't vibrate lose. I have 1/2 hardware on the top edge and 3/8 thru the side so those go into solid glass. You could get away with bolting them straight down and probably never have a problem have you Guys seen some other engine installs. I don't recommend this but I bet it would hold up so any cap I feel would work. Hell I seen mounts bolted through stringer that are wood with a little bit of glass over them. I did the 6061 C channel and run it at 23 kts offshore for 4 years so far No problem have cracked other things in the boat but not in the Bilge

I see the area you question looks like someone has done something there is that filler? Maybe you can grind near one of the holes and see if its glass and how thick is the glass.

 

[34Hatt]

I may be misinformed, but I always thought that Hatteras had included a steel plate in the lay up of the top of the stringer in the engine area so that it could be drilled and tapped for engine beds. No???

Maybe in some but I can say there was no metal plates in mine but as said above Lots of glass.

 

[danshat]

Had a guy out the other day who told me the stringers needed to be removed, everything ground out and new stringers installed, for a grand total of about 9K. I am in the process of a second opinion of course but I was wondering if 16lb closed cell foam with some heavy on the glass patches would be an effective fix? any ideas?