volvo 305 to 350 swap ECM issues?

the man

Petty Officer 2nd Class
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So, bought a 2006 305 GXI with a cracked block. Engine # 3869309 5.0 GXI-F. Volvo wanted $5500 for a long block, at the time I thought that was a bit much. I removed the engine and tried to source a replacement. During my research, I was told several times that a 350 would be a 'bolt in" application, "we do it all the time" - direct quote from a local marine engine supplier. So I got a new 350 short block, and used the old (100.7 hours) heads, cam, flywheel, intake, etc. Now it starts right up BUT:

Runs rough at idle. Surges up and down 100- 400 rpms, sometime settles down to a consistent 700-800 rpm idle. With no load and a little throttle, it was surging 400-600 rpms, then same thing, sometimes settling down. Test ran it in the water, same thing at about 3000 rpms- runs smooth, but surges up and down. When I back off on the throttle from 3000 rpms it dies every time.

I have read this thread: http://forums.iboats.com/volvo-pent...volvo-penta-305-350-running-rough-310708.html . BUT on mine, the ECM is not programmable; apparently it is an "E" type and Volvo made it so that it is not changeable? This is what I have been told by the boys that should know including the dealer.

Speaking of the dealer- They tell me that a new ECM is $1500, and might not work, "too many variables" they say. I told them there are no variables- I have a 350 block and everything else is from the original engine. Their response? If it doesn't work there are no returns on electronics. Thanks guys.

I have heard everything from I need to get a new- programmable- ECM (which would mean a new harness also) and program it, to "get a 305 and put it in". What if it isn't the block size though? It is reading no codes, and we are at a loss. Everyone has a different opinion; I have also been told that the computer takes a while to "learn" the engine and just to run it a while. I could write a book just on all the different theories.

So, next steps? Thanks in advance.

edit: full set of numbers listed on engine
3869309
4012191556
5.0 GXI-F
 

Don S

Honorary Moderator Emeritus
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62,321
Re: volvo 305 to 350 swap ECM issues?

You need a different ECM, one from a 5.7Gi-G (Not F, wrong style) PN is 3885452

The injectors are the same, and the wiring is the same as the 5.0GXi-F.
Your 5.0L ECM will be running the engine too lean.
 

the man

Petty Officer 2nd Class
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Messages
182
Re: volvo 305 to 350 swap ECM issues?

You need a different ECM, one from a 5.7Gi-G (Not F, wrong style) PN is 3885452

The injectors are the same, and the wiring is the same as the 5.0GXi-F.
Your 5.0L ECM will be running the engine too lean.

I love an answer that does not have the words "I think" or "it might be". Thanks Don

Will post with results.
 

the man

Petty Officer 2nd Class
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Re: volvo 305 to 350 swap ECM issues?

ps- any ideas where to source this besides the dealer?
 

the man

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Don S

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Re: volvo 305 to 350 swap ECM issues?

Volvo stopped using MEFI in 05 and went to EGC and EVC.
Merc stopped in 01 and turned to the 555.
 

Tail_Gunner

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Jan 13, 2006
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6,237
Re: volvo 305 to 350 swap ECM issues?

Thanks for that. Already talked to him- he was the first to give me the bad news. Not programmable / no bueno.

Ran it again and getting a bit of backfire- I suppose probably from the lean condition as Don pointed out.

Top Quality Source for Boat MEFI ECU Tuning | CO, KS, OK, TX, NE, AR, MO | MEFI Tuning

Those guy's have harness's set for for conversion's you might try them i dont know if it cost effective but the rusults would be great.
 

Don S

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Re: volvo 305 to 350 swap ECM issues?

I will ask this again, why would anyone want to go backwards and have to change wiring harnesses and buy an ECM to go to the older style MEFI ECM? MEFI is outdated. Troubleshooting the newer systems is so much nicer, and with more info.

Going back to MEFI from the EGC system, is like going from electronic ignition to a points ignition.
 

Tail_Gunner

Admiral
Joined
Jan 13, 2006
Messages
6,237
Re: volvo 305 to 350 swap ECM issues?

I will ask this again, why would anyone want to go backwards and have to change wiring harnesses and buy an ECM to go to the older style MEFI ECM? MEFI is outdated. Troubleshooting the newer systems is so much nicer, and with more info.

Going back to MEFI from the EGC system, is like going from electronic ignition to a points ignition.

Well not quite like that.....For engine mgmt a 4b can do anything that boat of his requires and is really beyond the engine..cheaper fully programable and marine certified.....Now one may not like the diagnostic software that is for sure and on small boats one is paying for a lot of tech not used...But you are right it is much more robust in feature's

Electronic Vessel Control - EVC (Electronic Vessel Control) : Volvo Penta
 

Don S

Honorary Moderator Emeritus
Joined
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Messages
62,321
Re: volvo 305 to 350 swap ECM issues?

Well not quite like that.....For engine mgmt a 4b can do anything that boat of his requires and is really beyond the engine..cheaper fully programmable and marine certified.....Now one may not like the diagnostic software that is for sure and on small boats one is paying for a lot of tech not used...But you are right it is much more robust in feature's

Electronic Vessel Control - EVC (Electronic Vessel Control) : Volvo Penta

The EVC system you linked to is not the EGC system the OP has in his boat.
That EVC is all fly by wire technology, all instruments, throttle and shift are all done electronically. It really came about with Volvo's new diesels, and is slowly starting to show up in the really high end gas engined boats. It takes a special computer to even diagnose the EVC.

I am referring to the EGC systems Volvo is using, Rinda even manufacturers diagnostic computers for the EGC that is even affordable to DIYers. Rinda Technologies - MerCruiser Scan Tool Spec.

Even if the person buys a different boat, his diagnostic computer is still going to work.

That is why I really dislike making a boats system one of a kind with aftermarket cheaper stuff to save a buck. Hard to get help for that kind of repairs. When it costs more, then it's even worse.
 

the man

Petty Officer 2nd Class
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May 26, 2007
Messages
182
Re: volvo 305 to 350 swap ECM issues?

Replaced ECM with part # 3885452. edit: Reacted a bit early on this (edited) post. Looks like it worked. I played with the timing a bit- do not have a light with me but new ECM appears to have been the cure. Once again, iboats saved me!
 
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