Our Community is 705,000 Strong. Join Us.


marine engines in street cars??????/


8.1 chevelle
02-15-2011, 08:06 PM
was wondering if anybody else was running marine engine in anything? I am running a 8.1 G,M, based Indmar marine engine in a 67 SS chevelle pushing 450 hp. 560 tq. a real blast to drive:screwy:

Moppie@af
02-16-2011, 11:02 PM
That is some nice power and torque, but most marine engines I've seen have quite a peaky power curve as they are designed to operate over a very narrow rev range.

Whats it like to drive?

MrPbody
02-17-2011, 08:43 AM
The most significant "differences" between a "marine" BBC and a car or truck BBC, are the head gaskets (marine engines require a stainless steel fire ring), the expansion plugs (marine requires brass) and the camshaft. The carb is also slightly different, "venting" the bowl into the venturi (avoids external fuel leaks, VERY important on a boat...).

Change the cam, add an intake and "big" carb, and instant "hot rod"... (:-

FWIW

Jim

8.1 chevelle
02-17-2011, 05:14 PM
That is some nice power and torque, but most marine engines I've seen have quite a peaky power curve as they are designed to operate over a very narrow rev range.

Whats it like to drive?
This one will set you back in the seat from get go all the way to 5800 rpm thats where the rev. lim. is set at was sorta scary the first time i drove it:runaround:

8.1 chevelle
02-17-2011, 05:16 PM
The most significant "differences" between a "marine" BBC and a car or truck BBC, are the head gaskets (marine engines require a stainless steel fire ring), the expansion plugs (marine requires brass) and the camshaft. The carb is also slightly different, "venting" the bowl into the venturi (avoids external fuel leaks, VERY important on a boat...).

Change the cam, add an intake and "big" carb, and instant "hot rod"... (:-

FWIW

Jim
does not have a carb. it has a good sounding cam with all the power I ever use:screwy: short video on photobucket

MrPbody
02-21-2011, 09:33 AM
We've seen very few of the late-model EFI engines. It's only recently become acceptable to use injection due to safety concerns. (the "high-end stuff has had it for a while, now).

My post was simply to outline the differences between a "marine" and other engines. I have no doubt, the marine BBC pulls hard in the car.

PAX

Jim

MagicRat
02-22-2011, 10:49 PM
We've seen very few of the late-model EFI engines. It's only recently become acceptable to use injection due to safety concerns. (the "high-end stuff has had it for a while, now).

No EFI in boats? I'm curious as to the safety concerns.
Does this include electronic ignition?

I'm just curious because my boat has a GM marine block with a points-igntition, made 10 years after GM introduced HEI. I thought boats would have benefitted from HEI, so there must have been some practical reason they were not original equipment in boats.

MrPbody
02-23-2011, 09:29 AM
MR,

Not for certain, but I believe it was more a safety concern as far as reliability more than fire danger. Shade-tree techs lament the loss of points and carbs because one needs specialized equipment to diagnose problems with electronics. No tow trucks or curbsides on the water... Once the technology had been proven "over time", marine engines started getting the modern stuff. I don't know this for FACT, but it seems to be the "attitude" of marine engine suppliers. Makes sense...

Jim

8.1 chevelle
02-24-2011, 05:33 PM
I have worked at Malibu boats started in 98 running efi before I started Mastercraft and moomba is all running it also:confused:

MrPbody
02-25-2011, 08:56 AM
8.1,

I'm an old man. 10-12 years IS "recent"... (:-

Jim

curtis73
02-28-2011, 10:10 AM
I think you'll find that marine cams and stock street cams are nearly identical these days. Marine engines have a greater need for flat torque curves and being NOT peaky than a street engine, so they use some pretty recognizable numbers.

For instance, I have a stock Melling Mercruiser grind for a 350 that specs out to 194/204 duration on a 114 LSA. Nothing fancy about it, just a normal stock grind. Worked great in my station wagon, but ran out of breath at 5000.

In actuality, most marine engines these days are carbon-copies of what gets put in the street version. They add the brass freeze plugs, a bronzed lining in any aluminum water passage, a marine water pump, and mechanically speaking - that's pretty much it. It used to be that they ran larger bearing tolerances requiring 20w50 oil, but metallurgy has come so far in the last 30 years that they can use stock street tolerances and just use 10w30. The Marine Vortec 350 I have torn apart in my garage has a stock cast crank, two bolt mains, and the block and head castings are 880 and 062 respectively - straight off the street and into a boat.

The main concern with running a marine engine on the street comes if the boat was ever used in salt water with an open cooling system. If it ever circulated salt water, the salt will stay in the porous block casting forever. There is no way to wash it out. The problem is, salt and ethylene glycol coolant don't play well together. They can make some fun green jello.

MagicRat
03-04-2011, 09:54 PM
.

In actuality, most marine engines these days are carbon-copies of what gets put in the street version. They add the brass freeze plugs, a bronzed lining in any aluminum water passage, a marine water pump, and mechanically speaking - that's pretty much it. It used to be that they ran larger bearing tolerances requiring 20w50 oil, but metallurgy has come so far in the last 30 years that they can use stock street tolerances and just use 10w30.
r.

The differences between marine and auto engines (assuming the same architecture) is an interesting subject.

Traditionally, marine engines were considered to have more durable bottom ends, because marine engines must be able to run at full power, high (4500 +) rpms for extended periods of time, use that cars never see, unless in race conditions. So many components are more robust. However, I have wondered how necessary is this.... can one use a decent auto engine in a boat?

From this site (http://newboatbuilders.com/pages/fuel-2.html):

Marine Engines 101: I was participating in a forum on-line recently and someone asked, “why can’t I simply drop an auto engine into my boat, and use that?” In response I put together the following which I called Marine Engines 101.

1. Marine engines are generally based on commonly used automotive blocks. Up until the late 80's it could have been a Chrysler, Ford, or GM block. Newer engines are almost all based on GM blocks. A good example is the GM 8.1 Liter engine that is in my motorhome, in a lot of pickup trucks, and a lot of other vehicles. But that is basically where the resemblance (other than outward appearance) ends.

2. Marine engines usually run at much higher continuous duty loads than automotive engines. Auto engines run up to speed, then the transmission shifts and the RPM drops to save fuel and because all that power is not needed to keep the car moving at the same speed on level ground. A car cruising on a level highway at 60 mph is running at about 2500 rpm (rpm depends on the gear ratio of the differential), much lower than it's max torque, and using about 20% of it's rated hp.
(MagicRat edit: I think the hp required is even lower. Most cars get down the road at 60 mph on 10-20 hp, which is even less than the 20% stated)
Cruising speed on most motor boats is around 3/4 throttle. A marine engine at 3/4 throttle is running anywhere from 3500-4000 rpm or more (depends on the engine, propeller size and pitch, and the reduction gear in the transmission) and near it's max hp. It is generally running at or near max torque. So the loads placed on marine engines are much higher and they must be built to handle heavier loads.

3. The cam shaft in a marine engine is designed for heavier loads. Whereas in a car the cam is selected for general use over a wide range of rpm, the cam in marine engine is selected for max rpm and torque.

4. Because of the heavier continuous torque loads, rods, pistons, etc are stronger.

5. Because they run under heavier load they need more cooling water. So the water passages are larger in a marine engine and a more powerful water pump is needed.

6. Valves are generally heavier duty like in trucks.

7. The head is usually heavier with larger water passages.

8. A higher capacity water pump is required.

9. A higher capacity oil pump is required.

10 Carburetor: The carburetor on a car and on a boat may look the same but internally they are not. If the float sticks in the bowl and fuel flows out the vent on a car it goes out of the carburetor. On a marine carburetor it goes down the throat. Marine carburetors are not allowed to spill any fuel into the boat. Plus that, marine carburetors have different jets and setup because of the different duty cycle. They need to be tuned to run most effeciently at three quarters throttle, usually about 4500 rpm (the rpm varies depending on the engine).

curtis73
03-05-2011, 10:04 AM
Old-school metallurgy required the extra bearing tolerances. Older crank forgings (and castings to a lesser extent) had much larger variances in heat-related size changes. Since a marine application runs at much higher loads, the bearings saw typically higher temperatures. Those higher temps did two things; swell the metal and reduce the bearing tolerances, and raise the oil temps accordingly. Wider gaps and 20w50 were the solution.

Todays castings are not only strong enough to replace yesterdays forgings, but the metallurgy has improved heat expansion ranges allowing boats to use street-type specs and 10w30.

I am not an expert by any means, but I have torn down and built about 5 marine engines - mostly small block chevys and one 351 Ford. The Ford was a 1981, and it still had 4-bolt mains and a forged crank, but otherwise it had the same exact rods, pistons, heads, etc that you would find on the street. The one I'm building right now is a marine chevy 350 Vortec, and not only do the guts have the same exact casting numbers as the street version, it even uses the same carbureted intake casting number as the ZZ4 crate engine.

I'm continually shocked at how similar they are these days. With the exception of salt use in the water jackets, I have no problems interchanging them; street/boat.

534BC
03-05-2011, 01:21 PM
Aren't some of them reversed rotation ? If so, don't mistake that cam.

curtis73
03-06-2011, 05:28 PM
Aren't some of them reversed rotation ? If so, don't mistake that cam.

Not since the late 70's in I/O configuration, early 80s in Inboards. Since the introduction of reverse rotation lower units and transmisisons, the reversing of the prop takes place after the engine. They did that specifically to keep things simple.

Add your comment to this topic!