anyone rebuilt a Mercruiser 140?

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lovetowrenchit
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anyone rebuilt a Mercruiser 140?

Post by lovetowrenchit » Mon Aug 25, 2014 9:49 pm

Hi
I would like to know if you professional engine builders have ever fooled with 1986 Mercruiser 140 with the two piece rear main seal? I know it's not a racing engine, but i was hoping to get some rebuilding tips, if possible, there is not a whole lot of rebuilding info on some of the boat sights, just problem, and solutions that you have to weed through.

I know that it is a GM block, and was told that the engine is considered 1/2 of a sbc 350. I'm not sure if this is true?

I'm also looking for a cam bearing installing/removal tool for this engine. I feel like i need one for a sbc? but not 100% sure.

The engine has 4" bores and I think I can buy 350 sbc cast iron rings standard?

I just have a lot of questions, and would appreciate any input, advice, comments

thanks! for the help!

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Re: anyone rebuilt a Mercruiser 140?

Post by BrazilianZ28Camaro » Wed Aug 27, 2014 7:24 pm

Hello, I"m not familiar with the mercruiser 140, but by the pics Google show its the same engine we have here in Brazil wich equiped Chevy Opalas made from 69 to '90.

This engine derivates from the 153" engine wich equiped the early Novas. The version you have have 4" bores and its the Pontiac version of the 153" with a 8 port head.

Overhere, the '69 to '74 Opalas had the 153" (3.875" X 3.25")on the entry versions, '75 and later L4s are 151"s with 4" and 3" stroke. Your engine might be a stroked version of the 151", the 181" (3 liter) engine.

I have built a couple of those 151" engines , up to 200hp level, N/A.

Yes you can use a SBC cam bearing installing tool. You can use the SBC 350'' rings, but you have to check if the 350" pin height is the same on 350'' pistons.

No, this engine isn't a half 350".

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Re: anyone rebuilt a Mercruiser 140?

Post by rfoll » Sun Sep 07, 2014 10:03 pm

If it has a cross flow head, it's an Iron Duke, only barely related to the Nova 4 cyl. It might be the 3 liter version. They are also related to the Pontiac 301.
So much to do, so little time...

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Re: anyone rebuilt a Mercruiser 140?

Post by machinedave » Sun Sep 07, 2014 11:10 pm

They are 3.0L GM engines with similar traits to the 2.5 GM engine although they were never offered in a GM car or truck but different varieties were used in industrial applications like Tenant sweepers and of course marine use. I have rebuilt a few of them. They are very easy to rebuild. I think the most important thing to address on these engines is a very thorough crack inspection. I also like to clean the castings in a baking oven and shotblaster to rid the castings of heavy rust and scale from the lake water. The heads can crack in between the valve seats but they seem to crack most often across the deck surfaces between the center two cylinders and also on the valve cover side of the head. If it was used in a cold climate the block, heads and exhaust manifolds are likely to crack in many places. Many well intentioned boat owners drain the blocks of water but there is often a lot of sand and muck in there that doesn't always allow all of the lake water to get out and then they freeze in winter. I always perform a magnetic particle crack inspection on the castings and if it passes then I also pressure test the block and head at 55psi of pressure to see if there may be a leaking crack that the mag powder cannot get into and pressure testing may also reveal a casting that is heavily rusted and may have a pinhole coolant leak that our eyes cannot see. There are many variations of parts on the motor and the boats that power them so I always give my parts supplier the part/serial number on the block tag that's riveted on the bell housing area so you can get the correct rebuild and gasket kit. You can save money on rings buy buying them for a 350 chevy and you will have four rings to spare. Order E251K(sealed power) or 2M-139 (Hastings). If I remember correctly they also use 350 chevy connecting rods so if you need a spare they are easy to obtain. They have a press on cam gear that has a trust plate behind it that needs to be carefully pressed on. I will take two .004" feeler gauges and place them between the cam gear and trust plate(one on each side of the camshaft) and carefully press the new gear on the cam and as I'm getting very close I will feel for a slight drag on the gauges and then my thrust is perfect. I don't recall that the cam bearing I.D.'s are the same as small block chevy but I could be wrong since its been awhile.

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Re: anyone rebuilt a Mercruiser 140?

Post by ALKYAL » Tue Sep 09, 2014 10:01 pm

Why press it on? The timing set we used had a Steel crank gear and an Alum. Cam Gear. Just warm the alum gear to expand the bore +.003/.004 over cam fit size. Agree with the feeler gages for the thrust.
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Re: anyone rebuilt a Mercruiser 140?

Post by machinedave » Tue Sep 09, 2014 11:29 pm

ALKYAL wrote:Why press it on? The timing set we used had a Steel crank gear and an Alum. Cam Gear. Just warm the alum gear to expand the bore +.003/.004 over cam fit size. Agree with the feeler gages for the thrust.
We press a lot of bearings, bushings, ball joints, gears etc... for auto repair shops in my area so we have a huge Dake press and tons of fixtures that make it a very quick and easy task to press anything on or off. I don't think there is anything wrong with your way of heating and installing the gear. If I wasn't good with the press I would probably heat it up too.

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Re: anyone rebuilt a Mercruiser 140?

Post by Schurkey » Thu Sep 25, 2014 3:13 pm

rfoll wrote:If it has a cross flow head, it's an Iron Duke, only barely related to the Nova 4 cyl. It might be the 3 liter version. They are also related to the Pontiac 301.
Early Iron Dukes had the non-cross-flow heads. GM recalled them due to excess pinging. The GM "fix" was thicker head gaskets which reduced compression. As I recall, it also destroyed any "squish", so the engine was just as prone to ping after the "repair" had been completed; but was shy a few horsepower.

Only the bore/stroke (of the 151 Iron Duke) is the same as a Pontiac 301. This engine has more in common with the Chevy 6-popper; the 153 was a direct descendent of the 230-cube 6-popper of that time. The 3-liter version even has the Chevy bellhousing.

BE CAREFUL with casting selection. There are items where the same casting gets machined differently; the casting number of the replacement part can be the same as the cracked or broken part you have--but it won't work due to a machining difference. One example of this is cylinder heads. Match the heads to the head gasket; assure that no holes in the head are out-of-place to the matching hole in the gasket.

I'm told that BBC 1.7 rocker arms are a common upgrade for this engine. I've never done that, so you may want to do some research.

A buddy of mine has a 2.5 in an S-10. Had continual head gasket problems until he figured out the casting number/head machining differences. Installed an Ultradyne cam and had enough power to tow a broken-down full-sized pickup at highway speed (until the head gasket popped...again. Once he got the correct cylinder head, the engine became both powerful and reliable--two words that are never used when talking about a stock 2.5 Iron Duke.

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Re: anyone rebuilt a Mercruiser 140?

Post by lovetowrenchit » Sat Nov 22, 2014 8:18 pm

BrazilianZ28Camaro wrote:Hello, I"m not familiar with the mercruiser 140, but by the pics Google show its the same engine we have here in Brazil wich equiped Chevy Opalas made from 69 to '90.cool! in your research I'm sure you saw some pics of my 140 & 3.0 Mercruiser engines

This engine derivates from the 153" engine wich equiped the early Novas. The version you have have 4" bores and its the Pontiac version of the 153" with a 8 port head.I have read that information also, but didn't know about the Pontiac version, good to know

Overhere, the '69 to '74 Opalas had the 153" (3.875" X 3.25")on the entry versions, '75 and later L4s are 151"s with 4" and 3" stroke. Your engine might be a stroked version of the 151", the 181" (3 liter) engine. I believe your correct that the 151 maybe stroked to the 181

I have built a couple of those 151" engines , up to 200hp level, N/A.That is too cool...I don't think there is much I can do to improve the performance of this amercruiser

Yes you can use a SBC cam bearing installing tool. You can use the SBC 350'' rings, but you have to check if the 350" pin height is the same on 350'' pistons. thanks for the input. I took the block and matching marked parts to the machine shop, and just got all of them back last week, and stared the assembly of the short block

No, this engine isn't a half 350".thanks, that myth is solved

What else you want to know?
I'm sure I'll have more questions, if you don't mind


thanks again for all the input. I will respond to all comments, then post what I had done to the short block

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Re: anyone rebuilt a Mercruiser 140?

Post by lovetowrenchit » Sat Nov 22, 2014 8:23 pm

rfoll wrote:If it has a cross flow head, I don't think it's an Iron Duke, never offered in an auto before. I believe it is exclusive to the Gm mercruiser only, however the GM block is made in Mexico, go figureit's an Iron Duke, only barely related to the Nova 4 cyl. It might be the 3 liter version. They are also related to the Pontiac 301.
I think I had hear that too, somewhere, good info

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Re: anyone rebuilt a Mercruiser 140?

Post by lovetowrenchit » Sat Nov 22, 2014 8:44 pm

machinedave wrote:They are 3.0L GM engines with similar traits to the 2.5 GM engine although they were never offered in a GM car or truck but different varieties were used in industrial applications like Tenant sweepers and of course marine use.I have learned that this engine was also used in some commercial generators, and fork lifts, and good to know some history bout the engine I have rebuilt a few of them.that is good to know, because I'm rebuilding now, and may have some questions if you don't mind They are very easy to rebuild. I think the most important thing to address on these engines is a very thorough crack inspection. I also like to clean the castings in a baking oven and shotblaster to rid the castings of heavy rust and scale from the lake water.just to let you know I had the short block and all my marked parts taken to the machine shop, and have received them back, and are now assemblng the short block The heads can crack in between the valve seats but they seem to crack most often across the deck surfaces between the center two cylinders and also on the valve cover side of the head.this is good info, because soon i will have to take a closer look at the head. I have 2 heads 1 from the 1986 140 that has a larger intake valves, and used with the original dish pistons. the 1993 head has smaller intake valves and was used with flat top pistons. I;m not sure which head Ill be using, both will work, if I'm correct? If it was used in a cold climate the block, heads and exhaust manifolds are likely to crack in many places. that is what happened to the 1993 3.0 . i purchased the boat with the cracked block, and purchased the 1986 140 for the doner engineMany well intentioned boat owners drain the blocks of water but there is often a lot of sand and muck in there that doesn't always allow all of the lake water to get out and then they freeze in winter. I always perform a magnetic particle crack inspection on the castings and if it passes then I also pressure test the block and head at 55psi of pressure to see if there may be a leaking crack that the mag powder cannot get into and pressure testing may also reveal a casting that is heavily rusted and may have a pinhole coolant leak that our eyes cannot see.the machine shop tested the block and it has passed There are many variations of parts on the motor and the boats that power them so I always give my parts supplier the part/serial number on the block tag that's riveted on the bell housing area so you can get the correct rebuild and gasket kit.I purchased a Fel-Pro marine gasket set You can save money on rings buy buying them for a 350 chevy and you will have four rings to spare. Order E251K(sealed power) or 2M-139 (Hastings). If I remember correctly they also use 350 chevy connecting rods so if you need a spare they are easy to obtain.I do have a spare 3.0 with low hours, and plenty of parts, but that is good info They have a press on cam gear that has a trust plate behind it that needs to be carefully pressed on.The 1993 3.0 has the aluminum cam gear, and the 1986 has the neoprene? if that is the correct word for it, or is it fiber? I will take two .004" feeler gauges and place them between the cam gear and trust plate(one on each side of the camshaft) and carefully press the new gear on the cam and as I'm getting very close I will feel for a slight drag on the gauges and then my thrust is perfect. great info, my cam was in perfect condition, and cam gear wasn't removed, so no need to fool with the thrust plateI don't recall that the cam bearing I.D.'s are the same as small block chevy but I could be wrong since its been awhile.
I appreciate the info. I really learned a lot, and still may have some questions. i will also post what is currently going on with this engine, and where I'm at with the assembly

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Re: anyone rebuilt a Mercruiser 140?

Post by lovetowrenchit » Sat Nov 22, 2014 8:47 pm

ALKYAL wrote:Why press it on? The timing set we used had a Steel crank gear and an Alum. Cam Gear. Just warm the alum gear to expand the bore +.003/.004 over cam fit size. Agree with the feeler gages for the thrust.
thanks for the info, it is something I will remember, good stuff

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Re: anyone rebuilt a Mercruiser 140?

Post by lovetowrenchit » Sat Nov 22, 2014 8:49 pm

machinedave wrote:
ALKYAL wrote:Why press it on? The timing set we used had a Steel crank gear and an Alum. Cam Gear. Just warm the alum gear to expand the bore +.003/.004 over cam fit size. Agree with the feeler gages for the thrust.
We press a lot of bearings, bushings, ball joints, gears etc... for auto repair shops in my area so we have a huge Dake press and tons of fixtures that make it a very quick and easy task to press anything on or off. I don't think there is anything wrong with your way of heating and installing the gear. If I wasn't good with the press I would probably heat it up too.
good info to use both methods. I don't have a press, and if I needed to install the cam gear I have two choices, thanks

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Re: anyone rebuilt a Mercruiser 140?

Post by lovetowrenchit » Sat Nov 22, 2014 8:58 pm

Schurkey wrote:
rfoll wrote:If it has a cross flow head, it's an Iron Duke, only barely related to the Nova 4 cyl. It might be the 3 liter version. They are also related to the Pontiac 301.
Early Iron Dukes had the non-cross-flow heads. GM recalled them due to excess pinging. The GM "fix" was thicker head gaskets which reduced compression. As I recall, it also destroyed any "squish",I have read the same thing so the engine was just as prone to ping after the "repair" had been completed; but was shy a few horsepower.

Only the bore/stroke (of the 151 Iron Duke) is the same as a Pontiac 301. This engine has more in common with the Chevy 6-popper; the 153 was a direct descendent of the 230-cube 6-popper of that time. The 3-liter version even has the Chevy bellhousing.this is good info, the 140s and 3.0 have 350 sbc block from what I understand

BE CAREFUL with casting selection. There are items where the same casting gets machined differently; the casting number of the replacement part can be the same as the cracked or broken part you have--but it won't work due to a machining difference. One example of this is cylinder heads. Match the heads to the head gasket; assure that no holes in the head are out-of-place to the matching hole in the gasket.more good info. i have 2 heads one from the 1986 140 which has larger intake valves, and dish pistons, and the 1993 3.0 head which has smaller intake valves used with flat top pistons, not sure which to use, they both are identical bolt and mating patterns

I'm told that BBC 1.7 rocker arms are a common upgrade for this engine. I've never done that, so you may want to do some research.I maybe interested in this, further investigation is needed, and cash lol

A buddy of mine has a 2.5 in an S-10. Had continual head gasket problems until he figured out the casting number/head machining differences. Installed an Ultradyne cam and had enough power to tow a broken-down full-sized pickup at highway speed (until the head gasket popped...again. Once he got the correct cylinder head, the engine became both powerful and reliable--two words that are never used when talking about a stock 2.5 Iron Duke.
thanks for all the great info, and I may have more questions, if I may

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Re: anyone rebuilt a Mercruiser 140?

Post by lovetowrenchit » Sat Nov 22, 2014 9:25 pm

Well, I have some updates on the Mercruiser 140 with pics, if I'm allowed to continue with this thread. I know this is not a marine engine performance forum, so let me know what y'all think about moving forward. If it's okay to continue...I will post up tomorrow

thanks!

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Re: anyone rebuilt a Mercruiser 140?

Post by Schurkey » Sat Nov 22, 2014 9:44 pm

lovetowrenchit wrote:this is good info, the 140s and 3.0 have 350 sbc block from what I understand
NO. The 153/151/3L all have an entirely different block design compared to the 350. The bellhousing bolt pattern on the 153 and 3L, and maybe the bore spacing is similar to the small-block.

As I said earlier, the 153 was a four-cylinder version of the 230 six-popper. This engine family was revised more times than I can count; but the 3L block seems to have more in common with the 153 and the six-popper than with the later versions of the 151.

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