Like Tree0Likes

Difference Between Boat and Car Engines

Reply
Old 10-15-2007, 01:13 AM
  #11
Registered
 
Join Date: Oct 2004
Location: Newbury Park, CA
Posts: 1,425
Default

Quote:
Originally Posted by johnfharding View Post
I used stock gaskets so I'm guessing that 9 to 1 would be pretty darn close.
I forgot to mention that marine engines use head gaskets made of corrosion resistant materials, too. Marine engines often (but not always) have forged components, especially the crank and rods.

Michael
Michael1 is offline  
Reply With Quote
Old 10-15-2007, 02:00 AM
  #12
Charter Member # 55
Charter Member
 
Griff's Avatar
 
Join Date: Oct 2000
Location: Omaha
My Boats: .......32............. ...............Active Thunder....
Posts: 15,744
Default

Quote:
Originally Posted by White Knuckles View Post
If that's the case, then why can't they develop a transmission just like a car that can lower the stress on the engine?

That would be like shifting into high gear at 30mph and trying to go up a steep hill. A boat hull has a lot more resistance than 4 spinning wheels on a car.
Griff is offline  
Reply With Quote
Old 10-15-2007, 11:53 AM
  #13
Platinum Member
Platinum Member
 
BigSilverCat's Avatar
 
Join Date: Jan 2003
Location: Joplin, Mo
My Boats: 2016 50' Skater Catamaran , 2003 41' Apache Cat, 2003 36' Cigarette Gladiator
Posts: 2,467
Default

paint it blue and put a mercury sticker on it and you will have magically turned it into a marine engine.
BigSilverCat is offline  
Reply With Quote
Old 10-15-2007, 12:14 PM
  #14
Geronimo36
Gold Member
 
Panther's Avatar
 
Join Date: Sep 2002
Location: Elkton, MD
My Boats: 36' Apache Warrior / 22' Apache Scout
Posts: 11,838
Default

"Marine engines have an extra .001"-.003" bore clearance because of high load operation and cold water to the block. A cold block with hot pistons is what dictates the need for extra marine clearance."

http://racingsecrets.com/article_racing-10.html
Panther is offline  
Reply With Quote
Old 10-16-2007, 09:19 AM
  #15
Registered
 
Join Date: Feb 2004
Location: MT. JULIET, TN.
My Boats: '99 33 Outlaw HP 500's,
Posts: 3,698
Talking

Quote:
Originally Posted by Panther View Post
Usually, piston to wall, ring, bearing clearances are different on a marine engine because its running sustained high RPM's
People overlook this very important fact all the time. They are usually pushing a rope back to the dock!
kennyo is offline  
Reply With Quote
Old 10-16-2007, 11:10 AM
  #16
Platinum Member
Platinum Member
Trade Score: (1)
 
KAAMA's Avatar
 
Join Date: Oct 2000
Location: Western Michigan
My Boats: A boat?....What boat??? How about a galvarnized warsh tub wit a toranady strapped own da rear!
Posts: 4,329
Default

Quote:
Originally Posted by Panther View Post
Usually, piston to wall, ring, bearing clearances are different on a marine engine because its running sustained high RPM's.....high load operation and cold water to the block. A cold block with hot pistons is what dictates the need for extra marine clearance.
Quote:
Originally Posted by kennyo View Post
People overlook this very important fact all the time. They are usually pushing a rope back to the dock!
I agree with all of the above. Since the early 1980's I have seen lots of boat guys who had a machine shop that is used to building great car engines fail when they were in stalled in an offshore boat. Piston to cylinder wall clearance, piston ring end gap, valve guide clearances all has something to do with "thermal expansion". The weight of oil you use and keeping it cool is important as well.

Finding a good precision machine shop that builds a truly decent marine engine is hard enough itself. Even many of these guys and their machine shops who are used to building great car engines for the past 20+ years....they have a lot of pride and you can't tell them anything because they think they know it all because of their sucesses with car/street engines. Think twice before you take your engine(s) to a machine shop used to building car engines...street, drag strip, oval......no matter how good they are. It is usually hard for them to grasp the marine offshore engine thing.

Also, cam differences. The only thing I could think of that would even be close to a marine cam would be a tame hi-perf street legal cam. You have to consider the engine's RPM operating range and the application when used for a marine engine.

The best way I have heard a marine engine being described is: A marine engine is like a semi pulling a full load of heavy cargo up a mountain. The torque has to be there and you have to keep everything cool at the same time.

Sorry about the soap box presentation. Have fun.
KAAMA is offline  
Reply With Quote
Old 10-16-2007, 02:46 PM
  #17
Registered
 
fandango's Avatar
 
Join Date: Feb 2002
Location: Solomons Island, MD, Vero Beach, FL
Posts: 396
Default

Can anyone (specifically anyone who works/worked for either company or has FIRST hand knowledge- not I know someone who knows someone) answer the question of what is the difference between the short block that GM performance sells -ZZ502 - and the shortblock that come with the "marine engines" from 1800runsnew and the likes. We are talking about only the shortblocks (not heads, cams, etc). You can buy a GM ZZ502 shortblock for approx $ 4400 I think and the 1800runsnew total engine is about $ 5400. Is someone taking apart these shortblocks, changing/checking clearances, balancing and reassembly, and then charge only an extra $1000 for the entire motor?? Point is I have heard that the 415 horse 502 comes from a plain GM performance shortblock (forged piston, steel crank, 7/16 rods etc.) and the 500 hp was disassembled and changed/checked, balanced and reassembed. Sorry for the long post.
fandango is offline  
Reply With Quote
Old 10-16-2007, 09:07 PM
  #18
Registered
Thread Starter
 
Join Date: Sep 2007
Location: Hartsburg, Missouri
My Boats: 1986 269 Cobalt Condurre
Posts: 110
Default Thank All

Very interesting perspectives. I know for a fact the guy that machined my engine is very very very PROUD. He got Really , Really pissed off when I asked him if I should plasti gauge the bearing clearance's etc. He said no! Thats what you paid us for. ( I plasti gauged anyway ).Anyway, that said, It sounds like I would be better off not to put this engine in a boat, I know the crank and rods are not forged, I know the piston clearance and rod bearing, ring gap and etc is to manufacturer specs. My measurements showed the bearing clearances were on the tight side of the range and so were the ring gaps. I would assume those spec's are for automotive use. Sounds like I would be pushing my luck. I have no idea on the 502 question.
johnfharding is offline  
Reply With Quote
Old 10-16-2007, 09:56 PM
  #19
Registered
 
OkieTunnel's Avatar
 
Join Date: Mar 2001
Location: Oklahoma City, OK
My Boats: 35 Motion "Bring It" is "For Sale", 31 Warlock
Posts: 872
Default

I don't think anybody asked what you were going to put this in. If it were going in a light weight 16 foot jet boat it would probably work fine with the right impellor. We are on OSO so I assume it is going in something bigger.
OkieTunnel is offline  
Reply With Quote
Old 10-17-2007, 09:00 AM
  #20
Registered
 
Join Date: Mar 2004
Posts: 205
Default

I have done some experimenting with this I bought new a boat with a 350 mag blew it up and tore it down I found no 4bolt main cast pistons and crank nothing different than a 78 chevy truck engine. I even ran my 350 mag cam in my 78 chevy truck to see what it would do and how it would react I found not much different than the cam it came stock with. I even tore apart the starters one from the truck and one that said marine stamped on it and found no difference they were exactly the same. The water pump on the front of the marine motor went bad had a gm pt# matched up to a 68 corvette. I built a marine small block without using marine parts but with marine clearances except for carb, fuel pump, and alt and ign and it has performed flawlessly for over 700hours. So go figure.
k24u is offline  
Reply With Quote
Reply

Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Nordicflame
Hustler
3
06-23-2008 10:47 PM
bert g
General Q & A
25
08-19-2007 04:27 PM
VIPER7
Sonic
13
09-01-2004 01:13 PM
cougarman
General Boating Discussion
6
03-18-2002 11:04 AM
26scarab
General Boating Discussion
25
03-07-2002 03:03 AM



Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT -5. The time now is 01:31 PM.


Copyright 2011 OffShoreOnly. All rights reserved.