Whats the difference between 3817 and 3817t connecting rods for a Mercruiser 181???

jdvasher

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I am rebuilding my engine and apparently the connecting rods I have and need to replace are thicker than the typical ones. Does anyone have specs on them. Did the thinner rods just use wider bearings or was the crank and block different all together? I have read a few places that they are all the same rod but I am finding out this is not the case. Thanks
 

Scott Danforth

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its a GM 3.0 industrial motor (same ones powered fork lifts, gensets, trash pumps, etc.

save your money and buy rods for a 3.0 GM industrial motor vs buying from mercruiser.
 

jdvasher

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Thank you, I will look into this. Any idea on part numbers to look for?
 

fishrdan

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Don't know the specific answer to your question, but there were small and large journal 181 rods. Been 10 years since I rebuilt my 181, and not sure if there was a difference in the rod width, but the diameters are different. (I have the large journal engine, 1973 181CI 140HP....) Far as I know, the main bearings are the same, just different sized rods and rod journals.

Are the rods so messed up that they can't be resized?

I bought a engine rebuild kit from Green Bay Parts World, but other internal engine parts like rockers, water pump pulley, etc, from an automotive engine 68 ChevyII 153CI. Some of the parts even had the GM P/N stamped on them. External engine parts (pumps, electrical, ignition, fuel) have to be marine, no auto parts can be used.

FWIW, one of my cam bearings was oversized, from the factory by the looks of it, rear cam bearing. I had to run to the machine shop to have them cross it to something that would fit...
 

jdvasher

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Don't know the specific answer to your question, but there were small and large journal 181 rods. Been 10 years since I rebuilt my 181, and not sure if there was a difference in the rod width, but the diameters are different. (I have the large journal engine, 1973 181CI 140HP....) Far as I know, the main bearings are the same, just different sized rods and rod journals.

Are the rods so messed up that they can't be resized?

I bought a engine rebuild kit from Green Bay Parts World, but other internal engine parts like rockers, water pump pulley, etc, from an automotive engine 68 ChevyII 153CI. Some of the parts even had the GM P/N stamped on them. External engine parts (pumps, electrical, ignition, fuel) have to be marine, no auto parts can be used.

FWIW, one of my cam bearings was oversized, from the factory by the looks of it, rear cam bearing. I had to run to the machine shop to have them cross it to something that would fit...

I'm still trying to figure this out myself honestly. The machinist mentioned wider and I found a few places the mentioned 1.30" width vs .9xx" width so I assumed that's what is was. The rods could be reworked but if I can get new old stock ones for a reasonable price it would be my preferred choice. He was able to find 2 at a warehouse for 50.00 each, assuming they are that cheap because they only have two. the old ones would cost at least that to rework.
 

jdvasher

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I've been doing a little more digging into this, I believe a big part of my original problem is misidentification of the engine itself. The serial number plate showed this as being a 1986 +/- but based on the size for the crank and rods it appears to be quite a bit newer. From what I can tell, They used 5 different cranks, 1987-1998 (87 was as far as I went back).

87-89 #0423-3816

90+ #0423- 810842
#0423-810842T (1.037 - 1.043 wide rod journal) (I'm pretty sure this is the crank I have however the part number on the crank is a completely different number, N383778, that last 8 is a guess because its not very clear.
#0423-804957 (0.952 - 0.958 wide rod journal)
#0423-804957T01

I am wondering if the 42 and 57 and the end of the part numbers signifies the width of the rod journal or maybe just a fluke. I don't have any dimensional data on the other cranks to verify this but if anyone can help fill in the gaps it could be helpful. I am also curious is the "T" designates thicker or thinner diameter rod journals. I know mine is 2.100"dia which is also bigger than normal.

I am assuming at this point the short block was replaced and possibly with a industrial version because the part number on the crank is foreign to Mercruiser or general GM parts list I can find.


Honestly I can say, this is becoming quite the puzzle and now I am being pulled deeper and deeper into it. I know these parts are used elsewhere but there doesn't seem to be any cross reference.
 

Scott Danforth

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with the 3.0, there is 1990 and older, and 1991 and newer.

the crank and rods changed for 1991 production year to go to the 1-piece RMS.

however if you keep looking at Mercruiser stuff, you will get confused as mercruiser used plenty of 1990 motors well into the early 1990s to use up stock

use the block casting or simply look at the crank - 1-piece RMS or 2-piece RMS

all marine 3.0 motors come from GM powertrain industrial engine division. everything in the longblock is GM.

it wouldnt mater if they replaced the longblock from a forktruck...... because it is identical down to the fasteners, pistons, cam, etc. the 3.0 motor is the same, starting in the same parts bin in Tonawanda NY, and coming down the same assembly line

the manifold, rotating electrics, mounts, coupling and flywheel housing are specific to the marinizer (OMG, VP, Mercruiser)

so for internal parts...... source from GM

however that begs another question. since 3.0 motors are literally under $300 for a running motor (once you get the free boat, and pay to scrap the rotten hull). why would you rebuild one?
 

fishrdan

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$200 for a set of rods? I'd be looking for a rebuildable core engine before spending $200 on rods. Plus, rods don't need to be replaced unless messed up (bent, cracked, bearing spun too bad to resize, etc) and $50+- would most likely have the entire set magnafluxed and resized.

The rods from my 73' 181 were in spec, had them magnafluxed at the shop while they were pressing on the pistons, but I didn't have them resized. Other engine builds, I've had the rods resized....
 

jdvasher

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with the 3.0, there is 1990 and older, and 1991 and newer.

the crank and rods changed for 1991 production year to go to the 1-piece RMS.

however if you keep looking at Mercruiser stuff, you will get confused as mercruiser used plenty of 1990 motors well into the early 1990s to use up stock

use the block casting or simply look at the crank - 1-piece RMS or 2-piece RMS

all marine 3.0 motors come from GM powertrain industrial engine division. everything in the longblock is GM.

it wouldnt mater if they replaced the longblock from a forktruck...... because it is identical down to the fasteners, pistons, cam, etc. the 3.0 motor is the same, starting in the same parts bin in Tonawanda NY, and coming down the same assembly line

the manifold, rotating electrics, mounts, coupling and flywheel housing are specific to the marinizer (OMG, VP, Mercruiser)

so for internal parts...... source from GM

however that begs another question. since 3.0 motors are literally under $300 for a running motor (once you get the free boat, and pay to scrap the rotten hull). why would you rebuild one?

The main reason for the rebuild is that I am doing a complete restoration from the ground up. I had a good engine (except for a few worn parts). I really cant see putting that much work into a project and throwing in a question mark of a used motor.

As to the rods, I have the wider ones with the larger crank journals. Any idea how I can cross reference the numbers? I can fine the parts for the industrial engines for pennies compared to the mercruiser products. Would really like to find some more specifics on this. I have had several people tell me the same thing but haven't got anywhere with cross referencing these parts.
 

Scott Danforth

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The main reason for the rebuild is that I am doing a complete restoration from the ground up. I had a good engine (except for a few worn parts). I really cant see putting that much work into a project and throwing in a question mark of a used motor.

As to the rods, I have the wider ones with the larger crank journals. Any idea how I can cross reference the numbers? I can fine the parts for the industrial engines for pennies compared to the mercruiser products. Would really like to find some more specifics on this. I have had several people tell me the same thing but haven't got anywhere with cross referencing these parts.

rebuilding a 3.0 is about the same cost as rebuilding a 5.7

mercruiser bought the motor from GM. (GM bought some of the parts from Melling and perfect circle and prestolite, etc.) Mercruiser will charge between 5X and 25X for the parts because they by parts from GM and repackage.

cut-out the middleman.

you are over-thinking the parts process. take the motor to your local machine shop and have them open their cross-reference books. they have to do the machine work anyway. However its simple, using the casting number of the crank, it determines the rotating assembly.
 

jdvasher

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you are over-thinking the parts process. take the motor to your local machine shop and have them open their cross-reference books. they have to do the machine work anyway. However its simple, using the casting number of the crank, it determines the rotating assembly.

Thanks but your not really telling me anything I didn't already know. The engine is at a machine shop, the best in the area. One man shop and the guy has been building race engines for for 50 years. He has a long history with the old Iron duke which was what first brought me there.

I am trying to help dig up some information because his contacts are coming up with nothing. I keep getting responses that this is super easy to figure out and to just look at other sources to get parts cheaper but nobody actually seems to know where to look specifically.
 

Fun Times

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My original problem is misidentification of the engine itself. The serial number plate showed this as being a 1986 +/-.
What is the engine serial number and what area did you locate the serial number from?, An id metal tag down by the engine starter or on a sticker on top of the engine?...Are there 2 serial numbers by chance found on the engine at each location mentioned?

Also what is the engine block casting number?

87-89 #0423-3816

90+ #0423- 810842
#0423-810842T (1.037 - 1.043 wide rod journal) (I'm pretty sure this is the crank I have however the part number on the crank is a completely different number, N383778, that last 8 is a guess because its not very clear.
#0423-804957 (0.952 - 0.958 wide rod journal)
#0423-804957T01
How clear are the other numbers you found on the crank? Have a close up photo of them?

As noted in the following links below it's suggested that the numbers can be misleading enough that they give out one suggestion that the 8's could look like 3's. Maybe some of the other numbers on the crank have missed appearances as well.

Thinking maybe your number N383778 could be somewhat close to the other numbers that are listed elsewhere online but are hard to read/make-out clearly.

Is your engine a 1 or 2 piece rear main seal?

https://www.nlamarine.com/products/m...nt=10458830917

https://www.nlamarine.com/products/...ft-3-0l-140hp-4cyl-1990-1999-1-piece-oil-seal

http://www.crankshaftsupply.com/kits_gm.htm
3.0
4
74-93
Marine application used in Mercruiser and OMC engines with a two piece rear oil seal.
N393775, N398776, N9341352
44
18098
261M
3.0
4
94-99
Marine application used in Mercruiser and OMC engines with a one piece rear oil seal. Rod thrust width is 1.035".
N14094623, 14096624
54
18099
261M
3.0
4
94-99
Marine application used in Mercruiser and OMC engines with a one piece rear oil seal. Rod thrust width is 0.963".
54
18096
3.0
V6
82-85
E
Early engine with tall deck block and long connecting rods.
257, 404
40
14024
211
3.0
V6
85-88
L
Late engine with short deck block and short connecting rods.
377, 732, 819
40
14027
212
3.0
V6
97-02
R
Crankshaft has bolt on reluctor ring attached to the rear counterweight.
1255069, 90499243
41
18097
 

Scott Danforth

Grumpy old guy who plays with boats
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Messages
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Thanks but your not really telling me anything I didn't already know. The engine is at a machine shop, the best in the area. One man shop and the guy has been building race engines for for 50 years. He has a long history with the old Iron duke which was what first brought me there.

I am trying to help dig up some information because his contacts are coming up with nothing. I keep getting responses that this is super easy to figure out and to just look at other sources to get parts cheaper but nobody actually seems to know where to look specifically.

first, the 3.0 industrial engine is a bored and stroked version of the 153 cubic inch 4-banger that originally was designed for the 1962 Chevy II which was 2/3 of the 230 inline 6

the "Iron Duke" is a 151 cubic inch pontiac motor that came about in 1977 and lasted until 1993, and it shares only 6 bolts with the Chevy motor. and those are the 1/4-20 bolts on the valve cover. there is no other common parts

the 3.0 is made in the Mexico plant only and there are two variations. the 1990 and prior with the 1-piece RMS crank and the 1991 and later with the 2-piece RMS crank.

the crank for the 153 1962-1970 153cid, with casting number 8522, 3788522, 379082N, 5743014
the crank for the 2-piece RMS would be 1974-1990 181cid, 3.0L, with casting numbers N393775, N398776, N9341353
the crank for the 1-piece RMS would be 1991-1999 3.0L, with casting number N14094623, 14096624

so what crank do you have?
 

jdvasher

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Messages
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What is the engine serial number and what area did you locate the serial number from?, An id metal tag down by the engine starter or on a sticker on top of the engine?...Are there 2 serial numbers by chance found on the engine at each location mentioned?

Also what is the engine block casting number?

How clear are the other numbers you found on the crank? Have a close up photo of them?

As noted in the following links below it's suggested that the numbers can be misleading enough that they give out one suggestion that the 8's could look like 3's. Maybe some of the other numbers on the crank have missed appearances as well.

Thinking maybe your number N383778 could be somewhat close to the other numbers that are listed elsewhere online but are hard to read/make-out clearly.

Is your engine a 1 or 2 piece rear main seal?

[

The serial numbers matched (A540484) and yes they were located in the correct spots. as to the block casting number, I will have to check with the shop as I didn't write that down. I agree with you on the number, I was givin the number over the phone by the builder and he sad half of the last letter was missing but possibly and 8. Either way the other crank numbers are way of so it appears to be that crank, memory is a little fuzzy but I believe it was a 2 piece RMS. I did not realize at the time that there were two different motors so wasn't really paying attention

and thank you or the information.
JD
 

jdvasher

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first, the 3.0 industrial engine is a bored and stroked version of the 153 cubic inch 4-banger that originally was designed for the 1962 Chevy II which was 2/3 of the 230 inline 6

the "Iron Duke" is a 151 cubic inch pontiac motor that came about in 1977 and lasted until 1993, and it shares only 6 bolts with the Chevy motor. and those are the 1/4-20 bolts on the valve cover. there is no other common parts

the 3.0 is made in the Mexico plant only and there are two variations. the 1990 and prior with the 1-piece RMS crank and the 1991 and later with the 2-piece RMS crank.

the crank for the 153 1962-1970 153cid, with casting number 8522, 3788522, 379082N, 5743014
the crank for the 2-piece RMS would be 1974-1990 181cid, 3.0L, with casting numbers N393775, N398776, N9341353
the crank for the 1-piece RMS would be 1991-1999 3.0L, with casting number N14094623, 14096624

so what crank do you have?

Thank you,

It would appear that I have the 2 piece crank based on the casting numbers. So now that I know this, how do I cross reference to non-Mercruiser parts?

JD
 

Fun Times

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jdvasher Maybe the following info I just ran across will help you out some.

http://boatinfo.no/lib/bulletins.html#mercruiser-service-2003_13


 

jdvasher

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