1990 Mercruiser 4.3 engine interchangeability?

[CatriderF7]

Id appreciate a little help from some of you guys that really know these motors. Im in need of a replacement 4.3 block and was wondering what year range I can look at. I know I need to be newer than 86 for the old flywheel/coupler to bolt up to it. But im not sure what year they went from the mechanical fuel pump to an electric pump, but im fine with adding an electric pump if need be. I assume if I stay between 1987-1990 i should be safe? Looking to do as little modification as possible

 

[Bondo]

Id appreciate a little help from some of you guys that really know these motors. Im in need of a replacement 4.3 block and was wondering what year range I can look at. I know I need to be newer than 86 for the old flywheel/coupler to bolt up to it. But im not sure what year they went from the mechanical fuel pump to an electric pump, but im fine with adding an electric pump if need be. I assume if I stay between 1987-1990 i should be safe? Looking to do as little modification as possible

Ayuh,.... I think mine is a '93, or '94, 'n it has the electric fuel pump,....
If yer willin' to buy an electric fuel pump, 'n new intake, you can go all the way to the current production Vortec motor,...

 

[CatriderF7]

Wow I figured thered be a lot more changes. So I could use a block from a late 90s blazer or s10 pickup without having any issues besides needing to ad a fuel pump? Do you know if the marine distributor and intake from my 1990 will fit on the newer style block and heads from a 98-99 auto engine?

 

[CatriderF7]

I know the intake most likely will not switch over to the newer engine, but If i buy a newer marine intake will I be able to use my pre HEI distributor out of the 1990 on a 1998 engine that is HEI?

 

[achris]

History of the 262 V6... 'First generation' was the non-balance shaft engine. Used fluid mounts and ran from 1985 to 1992. The 'Gen II' was introduced in 1993 with a balance shaft and electric fuel pump. Mid way through 1996 the engine was updated again (and called a 'Gen +') to the 'vortec' with different heads and roller cam and rockers. The intake is the same for the 1st and second generation, but is different for the Gen +. The early intake used 12 bolts at 90 degrees to the heads intake side, the later (Gen +) intakes use 8 bolts and they go in vertical. All engine can use the same distributor. The Gen I and Gen II engines used Thunderbolt IV and the Gen + carbed engines used Thunderbolt V. The distributor itself is the same, the only thing different is the module on the side of it. The Gen + MPI engines use a completely different system, and is probably not relevant to what you're doing. No Mercury Marine V6 used a GM HEI. If your engine has one, it's automotive, not marine and you should 'cast it adrift'. HTH,

Chris......

 

[CatriderF7]

Thanks for the info. I havent bought an engine yet, just trying to avoid buying one thats going to cause problems when trying to swap parts over. I am looking at an engine that came out of a 1998 chevy blazer. Its a good running engine for $200. Basically what I need to know is if anyone knows what exactly I need to make this swap so that I can price parts out ahead of time. Parts on the boat such as carb, distributor, alternator, starter etc are all good so I would just be switching them over. As long as the flywheel bolt pattern is the same and the marine distributor will fit on the 1998 model engine, I think i would be good to go

 

[achris]

If your current engine is the older 'non-balance shaft' engine, you're also going to need new mounts for a newer engine (1993 and later).

 

[Volphin]

What I did on my 4.3 was build a non-balance shaft block that came stock with the roller cam and add the Vortec heads and manifold. All the balance shaft does is reduce vibration (supposedly) and eat some HP. You can find Vortec heads in the junkyard for $100-$150/pair. Have them rebuilt for $300. Short block will run 1500 or so. New intake: $200 on sale.

 

[Volphin]

No Title

The one I built has lots of goodies, but you can keep it simple and have a great engine. Always consider a closed cooling system for new rebuilds as well, because you can't add them later very successfully.

 

[Volphin]

Pics still are not working.

 

[CatriderF7]

That would be a nice, but what im looking to spend isnt anywhere near that amount. And If I were going to spend 1500-2000 on it I would put a 305 or 350 in it instead of the 4.3L

 

[Volphin]

Yeah, but if you did that, you would have to glass in new motor mounts... plus change the out drive.

 

[CatriderF7]

If your current engine is the older 'non-balance shaft' engine, you're also going to need new mounts for a newer engine (1993 and later).

When I look at buying an engine mount set for a 4.3 V6 I see a lot that say they fit 1988-1995. Are you sure they changed them in 93?

 

[CatriderF7]

Yeah, but if you did that, you would have to glass in new motor mounts... plus change the out drive.

I guess you could change the outdrive but I wouldnt think you would need to other than to have optimum gearing. Didnt think about motor mounts but I think itd be worth doing extra work for if your going to put that much money into it you might as well have more power than before

 

[Scott Danforth]

When I look at buying an engine set for a 4.3 V6 I see a lot that say they fit 1988-1995. Are you sure they changed them in 93?

yes, the information that Chris provided in post #5 is accurate.

if you go with a 5.0 (305), many had the same gearing as the 4.3

 

[CatriderF7]

Im looking at a 1994 Vortec engine now. It has the same looking mounts. The mount itself is different but the bolt pattern on the block looks the same as the ones on my engine (2 bolts on top, 1 on bottom centered) is there something else you were talking about or are the actual holes spaced differently on the blocks?

 

[achris]

The mount itself is different. The point it attaches to the block is the same. The older mount is 'fluid' to try and damp out the inherent vibration of a 90 degree V6... Once the balance shaft engine arrived there was no need for the fluid mounts, so the same mounts as the V8s use were fitted. But the height of the mount is different, so going from the fluid to the solid will require the mounting pad to be raised slightly. I don't know how the fluid mount will perform on the balance shaft engine, never done it...

Drive ratio... Use the same drive, no need to change. Some V6s had 1.84, some had 1.62. Doesn't really matter which you use, as long as you prop so it pulls between 4400 and 4800rpm at WOT...

 

[CatriderF7]

Ah alright, well my plan is to buy an engine and basically strip it down and put everything external off of my cracked block on it, including the mounts that are in the boat. So itll be fine then. I thought you were saying the actual block was changed requiring me to buy mounts that bolted on differently because mine wouldnt bolt to the 94 engine. The mounts from my 1990 are the same ones that are on any of the V8s ive worked on. Just a triangular piece of cast iron? with some rubber to dampen vibration