Repower 3.0 to 4.3 MPI

[mdchappell]

I am looking to repower a 2002 merc 3.0 to a late model 4.3. Can anyone give me any hints. The 4.3 is a marine block with auto heads and intake. All have brass freeze plugs and other required changes for marine use, I hope.

 

[Dakota47]

Re: Repower 3.0 to 4.3 MPI

It wont bolt up..

 

[Don S]

Re: Repower 3.0 to 4.3 MPI

You may need stringers & engine mount pads in the boat, as the 3.0L engine has a front mount and the 4.3 has engine side mounts. You will also need a marine ignition system compatable with a shift interrupt switch, is the MPI a marine version? If not it isn't going to work. Complete exhaust system, including the Y pipe that attaches to the transom shield. Will also need to change the upper gears in the outdrive to a different ration (NO, you can't just change props and get away with it). Then there is the coupler, and who knows what else.
Sure there is room in the boat for it? It's wider than the 3.0L

 

[mdchappell]

Re: Repower 3.0 to 4.3 MPI

After reading more posts onm this forum and others, I think Im going to try to find a 4.3 that maybe is blown. I know the block is good on mine, but Im just not sure about getting all the extras/S pump, water lines and adaptors and who knows what else. As for it fitting, my boat was available with the 4.3l in the same interior configuration. Provisions for the mounts are in place. What part will not bolt up, bellhousing or what?

 

[imported_TheMan]

Re: Repower 3.0 to 4.3 MPI

Although my original boat and replacement motor are significantly older, I did a similar swap.

As a summary of my experience:
Buy junk boat with decent motor.
Haul out engine. Disassemble, inspect, replace gaskets, repair, prime, paint.
Fabricated some T shaped mounts to run off existing stringers and attached engine mounts to them.
Installed Y-exhaust from junk boat.
Install engine.
Drive around.

The 4.3L I purchased was connected to an Alpha I Gen 2 and I installed it on an original Alpha I with no problems.

Don has the experience and know how, so I don't mean to contradict him with my limited experience, but as of yet I have not switched out drive ratios (I am saving up for a replacement drive from SEI and am using the current 2:1 ratio). I believe when Don says that you must replace the gear ratio, he is referring to having top end, or maybe even the overall best, performance (please correct me if I am wrong, Don!). Since I use my boat for wakeboarding mostly at the moment, I am not really concerned with top end performance and actually more so the bottom end. I expect that the 2:1 ratio gives me better hole shot (no proof!). Regardless, the operation of the boat is 10x better than it was with a 3L, without the outdrive swap. There is obviously a danger of over-revving the engine though, but I don't run WOT much.

 

[cmcpherson]

Re: Repower 3.0 to 4.3 MPI

If you have to ask what bolt up, do you really think this is something you should undertake???????????

 

[imported_TheMan]

Re: Repower 3.0 to 4.3 MPI

cmc, I did the swap and don't know what you think/say won't bolt up either.....
Only thing I can ASSUME you are talking about is the exhaust or POSSIBLY the engine mounts..

 

[cmcpherson]

Re: Repower 3.0 to 4.3 MPI

Point is quite simple, if you have to ask what it could be, you are not prepared to undertake the job.

 

[imported_TheMan]

Re: Repower 3.0 to 4.3 MPI

I politely disagree.

Anyone who thinks they know what every step of every job is going to be is a fool.

There are almost always quirks with any job you undertake, especially on a boat. If it were cut, dry, and easy everyone would be doing it. You might have to do some work, do some reading, and learn a few things on the way, but rest assured, there is a way.

If you are willing to accept that and understand you may run into problems, then you are prepared to undertake the job. So, MD, if you want to upgrade, upgrade! Just be careful and remember lives are at stake.

 

[cmcpherson]

Re: Repower 3.0 to 4.3 MPI

Ok, If You Can't Even Figure Out The Basics, How Are You Going To Figure Out The More Complicated Stuff?

 

[tommays]

Re: Repower 3.0 to 4.3 MPI

How is it that anybody knows what fits with what and which years the flywheel size changed without asking someone else who new more then them at the time

Or the really obscure stuff like the year the 14" flywheel does not clear and you need to buy the volvo kit to make it work

 

[cmcpherson]

Re: Repower 3.0 to 4.3 MPI

EDIT By Don S

That's enough!

 

[Don S]

Re: Repower 3.0 to 4.3 MPI

cmc, NO MORE COMMENTS, he has a right to ask the question.
If you want to flame people for asking questions, find another forum.

Back to the original topic of what will and will not work.

 

[cmcpherson]

Re: Repower 3.0 to 4.3 MPI

whatever, this place sucks!!!!

 

[JB]

Re: Repower 3.0 to 4.3 MPI

Bye, cmc.

 

[Limited-Time]

Re: Repower 3.0 to 4.3 MPI

OK..................Bye, Bye............

 

[Limited-Time]

Re: Repower 3.0 to 4.3 MPI

Dang it JB Ya ZAPPED him while I was typing..........

 

[mdchappell]

Re: Repower 3.0 to 4.3 MPI

Thanks guys. On the issue of "Bolt Up" I was refering to the fact that I didnt know if he was referring to the bellhousing or the accessaries. The idea of buying a junk boat is appealing. Let me through another idea out there. Thru hull Exhaust. By the way. What year engine would I need to use or does it matter since I will have to replace the bellhousing anyway.