Info on Exhaust Manifolds for diesels

SS MAYFLOAT · Dec 7, 2003

Wanting to repower my boat with a diesel. I don't know a whole lot about marine diesels only that they are big bucks. Was thinking of a pickup truck diesel and converting it, but the exhaust manifolds needing to be water cooled, I'm at a loss in even trying to look. Any ideas on this subject? It is not set in stone that I am going to do this. Just looking for the lease expensive way to get better low end torque. Thanks....SS

Seaboo2 · Dec 7, 2003

Re: Info on Exhaust Manifolds for diesels

Two things: first you may want to read this: http://www.yachtsurvey.com/GasDiesel.htm It discusses a big con of this Here is a company that offers a kit using a dodge cummins engine: http://www.hsmarineservices.com/

Walt T · Dec 7, 2003

Re: Info on Exhaust Manifolds for diesels

Mayfloat, What is your boat? Size? Brand? Planing, displacement, current power? How do you use it? Why are you even considering a diesel changeover?

rodbolt · Dec 7, 2003

Re: Info on Exhaust Manifolds for diesels

hello I gotta agree with seeboo2. I cannot make people understand that for heavy continuos commercial serviuce a large slow turning diesel will go thousands of hours. most smaller high revving play diesels are relativly short lived. most of the life expectancy is due to customer neglect on both gas and diesel. in our saltwater here the average life span of a saltwater cooled engine is about 6 years regardless of hours used. the salt does not care it corrodes. risers and maniflds usually go about 3 years. some volvo diesel only 2 due to the corrosive effects of the fuel by-products after combustion. I cannot get any of my customers to toss 1200 plus dollars worth of manifolds in the trash before they wipe out 16,000 worth of engine. most will wait until the engine is junk due to bad riser/manifold then cry about the package replacement cost.I have seen more diesel fires in boats than gas fires. most all gas fires here have been traced to insurance fraud or improper parts/maint. like the guy who uses rubber lines between the pump and the carb. now SS

why do you want disels? what type of drives or transmissions do you have? the type C volvo will take most small diesels below 340 HP. stay away from mercs they dont like gas much less diesels. the 6.9 ford has been marinized by starpower and they could help with one for you. good luck and keep posting. but if ya really want to play go with the 8.1 volvo EFI

a sweet beast.

SS MAYFLOAT · Dec 7, 2003

Re: Info on Exhaust Manifolds for diesels

Okay, here we go. Sorta been through this before a couple of years ago. Boat 27'x 8', Bayliner Victoria w/flybridge dual helm Outdrive is ChrisCraft but the exact same as the Volvo 280 and is powered with a 350 with Chriscraft manifolds. Sleeps 6, Head, Galley, Dual voltage fridge, microwave, stove oven combo, 2 - 20 gallon fresh water tanks, 30 gallon holding tank, dual heat water tank, and 100 gallon fuel tank. So she is fully equipped minus built in genset. However I carry a portable generator that weighs about 70#. I only use the boat in fresh water during the 6 month season. Of course mainly weekends, but sometimes live aboard for several weeks at a time. Last couple of yeas I mainly have spent time just at the dock due to the poor performance. With two medium sized people on board, holding/freshwater tanks empty, fuel tank half full, no personal gear onboard, and no supplies, this boat will barely get up on plane. It takes about a quarter of a mile to get it up at WOT. Then once it is up on plane and taching out, pull the throttle back to about 3800 rpm, boat settles back down in the water. It is just working too hard to plane out. Awhile back Slowly Sinking said he had the same boat and he had the same problem. I have checked around with others and basically the same problem. I have changed props without solving my problem. When I go to a smaller prop, it gets up on plane faster, but cannot maintain its planning at a lower rpm. I have considered going to a BB/454 for the repower to deal with the underpower problem. Now for my intended use of the boat. My wife and I intend on traveling alot on the riverways within the states. The number one concern is my wife does not like to go fast up on plane. She finds it frieghtning to the utmost. Believe me, I've had bruises where she has beat the crap out of me for scaring her. I would like to be able to cruise between 15 and 20 knots a be effiecient. With the gas engine at this speed, the fuel guage drops quickly for the distance traveled. I have a friend that operates a recycling yard and get just about any engine that I need. Of course I am aware about land bound engines vs marine engines as far as the spark arrestors go. I have read lots about how it is not cost effective to go this route and how the corrosion problems that exist in diesels while they are not operating. However my boat would get much more use if it would satisfy me in its ability not to suck gas so bad for the low speed in which I want to cruise. Sorry to make this long, but I was just trying to give a detailed description of the boat and my intentions on its use. Thanks......SS

SS MAYFLOAT · Dec 7, 2003

Re: Info on Exhaust Manifolds for diesels

BTW Tabman has tried to help by recommending me a certain size trim tab. I did increase the tabs in size along with the ends being bent down. Did help some, but not that noticable......SS

Walt T · Dec 7, 2003

Re: Info on Exhaust Manifolds for diesels

The 454 with a properly geared drive and proper prop should be fine. Duo props would be even better. At sea level 1:65 gears should be okay. You ought to be able to turn a 17 pitch single prop. 1:95 gears will require props in the 21 pitch range. The 1.95 gears and a 21 pitch prop will get you about 40 mph at 4400 figuring approximately 10% slippage. The 1:95 gears will help that big boat get up on plane even with the steep prop. The 1:65 gears with the 19 is about 44 mph which is a little optimistic. I think a 17 pitch with a 1:65 ratio and the 454 will get you about 38 mph at 4400 rpm (approximate wot) and a cruising speed of about 25 mph which is about right. A good steel 4 blade should work well.

rodbolt · Dec 7, 2003

Re: Info on Exhaust Manifolds for diesels

hello wow your wanting the best of both worlds

. that is a big heavy pig boat and that puny motor wont hold it on plane at 1/2 throttle. I would rather see a repower with a 7.4 or an 8.1 but that 280 outdrive is going to be a bit of a problem. that drive is rated at 280 horsepower. hence the 280 designation. it was badly underpowered when it was new and did not get better with age. they are very nice boats though just most were under powered. most diesel applications will require fuel tank mods to return excess fuel. the international/ford 7.9 is common and its already been marineized by starpower. the bellhousing choices to mate with the volvo transom sheild will be a problem. if you go diesel and keep the current outdrive it will need to be updated with the new Nedox style cone. good luck and keep posting

SS MAYFLOAT · Dec 7, 2003

Re: Info on Exhaust Manifolds for diesels

Thanks for the replies Diesel Walt and Rodbolt. I'm in an area in which I want to please my wife, but I'm tired of "The Slow Boat Under My Hinney" I just hate to make the mods to make it an efficent displacement boat and then having problems selling it in the future due to it being slow. I was told several years back on this forum that the 280 outdrive would be okay with a bone stock 454. That is providing it is operated with caution in not hammering on the takeoffs as well as quick throttle return. (I've heard that hard backlash on the outdrive is just as rough on them if not harder. I have never grenaided an engine or outdrive in my 25 years of boating. My neighbor has an old 327 ZR that he claims would be excellent for my boat. He says it develops 375 hp, but I have told him that I can't run the rpm that 327 needs to develope the hp. Would this maybe a canidate to use? If it would put out the low end torque needed? Just another question. Okay.....the idea of a diesel is out. Will start putting together the things needed to get a 454 going on. Thanks again, you have been a big help. SS

Walt T · Dec 8, 2003

Re: Info on Exhaust Manifolds for diesels

Your neighbor is delusional. However it was kind of a trip down memory lane to think about that old 327. In 1965 it was produced at 250 HP. In 1966 it was upped to 275. There were optional versions of that engine that went to 350 HP. Keep in mind that these horsepower figures may sound fantastic, but a different rating system was used to find horsepower in those years. Depending on the number of power options on the car, the total "net" horsepower (the rating system used today) could drop from between 20-40% of the "gross" total. So his "375" hp would actually be more like 225-300 hp by todays standards. And if that is a 1965 engine then it would be 125-200 hp by todays standards. Hardly what you want. The 280 will work with the 454 under normal use, but if it were me I'd trade up to a 290 and install a duo prop lower. You wont regret it.

Bondo · Dec 8, 2003

Re: Info on Exhaust Manifolds for diesels

SS, You answered your own Question about the 327..... Displacement builds Torque down low.... The 327 Won't make the power you Need, at an RPM that's Usable........ An overbore of .030,+ a Stroker Kit(383cid) in your 350 can easily make 350/375HP, Under 5000RPMs.... This is what I'm doing for the Project I'm building now.... The 7.3l Navistar/Ford Diesel was/is used by Mercruiser Also..... I'm building my new motor well big enough so this combo will also fit, as it's My Ultimate Goal.... Just because I'm a Diesel kind of Guy..... I've got the Engines, I just need the Merc. Manifolds to make the conversion.....So, If Anybody knows Where I can find a set, either with or without the turbo, I'm Interested................ Another Option that Might help you is the Dual-Prop outdrive..... I Think the 280 is convertable to the dual-prop....

Wellcraft Excel · Dec 29, 2003

Re: Info on Exhaust Manifolds for diesels

Hello.. I live in Norway and my engine is an 7,3 IDI turbo diesel. with starpower manifoils. I also wonder where to get new ones. The rest is mercruiser.. Engine runs like he....l

Info on Exhaust Manifolds for diesels

Admiral

Petty Officer 2nd Class

Lieutenant

Supreme Mariner

Admiral

Admiral

Lieutenant

Supreme Mariner

Admiral

Lieutenant

Moderator

Cadet