Mercruiser 165 EFI conversion

[justin146]

I am a tinkerer. I have been considering converting my 250 chevy Mercruiser to EFI. It seems pretty straight forward to me. I'll find a spot on the exhaust manifold that doesnt have water jacketing and drill for the o2 sensor, or fab up a 1 inch spacer between the manifold and elbow for it. Then use a Rochester 2 barrel to chevy TBI adapter on the intake. Either that or make an adapter plate that will mount a 4 barrel unit, like the FiTech. I wont have spark control, but I am ok with that. I remember somewhere that there was a computer controlled distributor for 84 model trucks that could be adapted- But now I cant find one or any info on one.

I've seen plenty of v8 conversions, and the adapters for oxygen sensors are readily available. unfortunately the pattern for my elbow is different. I have a 3 axis cnc in my garage and can probably knock the spacer out in a few hours.

Any thoughts?

 

[kmarine]

It is far more complicated than that. you need a high pressure fuel cell seprate from the fuel tank. a second fuel pump to feed the fuel cell. special uscg approved linesl not to mention that early efi systems from ford racing mercruiser and Volvo are still plagued with problembs that haunt boat owners from 1994 to about 2003. holly pro-jection and Fast fuel injection still have issues with retrofitting. I have a boss gt40 racing engine made by PCM and 6 dealers and a ford racing tech cannot tell me why my computer hesitates at 3500 rpm you can purchase a new boat for what you will spend in parts before you get it right.

 

[o'neal]

I posted about injecting my mercruiser 120 once...... must meet regs and specs of uscg.around my parts on certain lakes i could be checked and I didn't feel like explaining or a ticket.the carb and points work just fine for me.why do you want to convert to efi?

 

[justin146]

Actually I plan to do a full high pressure system with inline pump after the fuel tank selector. And another selector for the return lines I'll run. I plan to do the tuning myself. I've done a couple EFI systems on cars before. The only hard part I see is the O2 sensor location.

 

[justin146]

I really wanted to swap in a 4.8 truck motor I have, but I want to keep the interior stock. The doghouse isnt wide enough. This is my consolation prize

 

[Scott Danforth]

Unless the parts you intend to use are J1171 listed and compliant, i wouldnt do it.....boom

You will actually lose a bit of top end power moving to EFI from a carb.

In my mind, not worth it

 

[khe]

Actually I plan to do a full high pressure system with inline pump after the fuel tank selector. And another selector for the return lines I'll run. I plan to do the tuning myself. I've done a couple EFI systems on cars before. The only hard part I see is the O2 sensor location.

I don't think the early marine EFI systems (the TBI systems and the early MPI systems) use an oxygen sensor. They run in open loop mode. Unless you're all compliant with Coast Guard regs., it's probably not worth it from a safety point and a hassle standpoint as O'Neal described.

 

[justin146]

Thoughts on this "marine" kit?

http://www.ebay.com/itm/EFI-Complet...50-5-7L-MARINE-APPLICATION-BOAT-/321764729811

 

[justin146]

My thoughts after reading a bunch of posts about USCG regulations- A quadrajet to TBI adapter, using a TBI from a boat (even though they are exactly the same as automotive ones). NO timing control, so stock distributor. USCG approved fuel lines and pump. And control with with my Megasquirt with a wideband in a spacer between elbow and manifold.

This would fully comply with regulations- or the interpretation of regulations by people here. Which dont cover EFI at all. Because they are from the 70s.

And for the people that say it will be expensive- I don't really care. Money is not an object on this honestly.

 

[harleyman1975]

As you can probably tell I-boats is not a hot rodders web site. It is more geared towards helping the average Joe keep his boat running safely and cost effectively. I know for a fact that there are guys here that can do amazing things with non stock engines but the forum tends to try to encourage people to keep things as stock as possible (to ease parts sourcing) and safe (uscg compliant). I think it is cool what you are trying to do personally and wish you success. Let us know how it turns out!

 

[Scott Danforth]

My thoughts after reading a bunch of posts about USCG regulations- A quadrajet to TBI adapter, using a TBI from a boat (even though they are exactly the same as automotive ones). NO timing control, so stock distributor. USCG approved fuel lines and pump. And control with with my Megasquirt with a wideband in a spacer between elbow and manifold.

This would fully comply with regulations- or the interpretation of regulations by people here. Which dont cover EFI at all. Because they are from the 70s.

And for the people that say it will be expensive- I don't really care. Money is not an object on this honestly.

While you may believe you meet the requirements, you have to legally test the system and have it certified

Marine TBI units are not the same as automotive. There are more shaft seals to prevent any fuel leaks,

The latest 33 CFR 183 sub section J covers all fuel systems

I applaud building EFI systems, just not on boats with closed bilges where the risk of explosion is real

 

[GA_Boater]

I would feel safer with MFI over TBI. But really if I wanted FI, a newer boat or full repower is the way to go. IMHO of course, I'm not spending the dough.

Be safe about it, Justin.