TBI conversion kit for older boats

[Rawleigh]

Has anyone tried a TBI conversion kit on any of the older V8 in our boats? I ran across this website and it got me thinking about how much it might increase fuel efficiency over a 4 barrel carb. Of course at $1,175.00 each for my 440's, I could buy a lot of fuel. They might be more cost effective for someone who wanted to extend their range without changing tanks though.

http://www.affordable-fuel-injection.co ... -19-1.html" onclick="window.open(this.href);return false;

[1962 31]

haven't done any on a boat but im converting a 72 chevy blazer to a tbi set up next week and have done some others at my shop fuel injection is the way to go! start easier better economy and don't gum up if it sits for a few weeks. my next idea is fuel injecting my 71 Honda cb750 stand alone ecu with new style injectors and throttle bodies. I hate carburetors

[mike ohlstein]

Yeah, but I could (or could at one time....) tune your Honda with a screwdriver, a pair of pliers, and my ear.

Now you need a computer.

[Bruce]

I did a pair of small blocks in a Bertram 28 when they first came out. It was for a sheriff's deputy friend of mine who had gotten hit by a car on 95 while making a traffic stop and was looking to save fuel costs.

They were a disaster. I put a ton of hours into that project with horrible results.

That was a few years back. I would think with advancements in the computer and programming that it should be better.

But unless a system has all the sensors and a distributor that is plugged into the ECM, your not going to get the same results as a complete closed loop EFI system. Just using a temp sensor with an EFI system isn't going to cut it.

Until engine temp comes up it is going to run rich heavy and plug fouling is a reality. Over the road systems are not as crtitical as marine due to the operational performance curve differences.

If I'm not mistaken by your link the cost is 17 and change for your engines plus another 3 to 400 for the distributor.

Throttle bodies ran a very short time in the marine industry and then went to MPI. I had nothing but trouble with TBI systems with plug fouling, back firing which will take out a TBI injector and upper end fuel delivery.

The simplistic way a TBI or MPI system works is it measures the air flow and only delivers the fuel needed to take advantage of the air flow at a given rpm rather than try and burn a over rich mixture where unburned fuel just gets thrown out the exhaust.

Anyone can understand from that description that unless you have all the components in a system to take to measurements which btw changes with temp, getting the most for your dollar is impossible.

I'd insist the manufacturer send you contact info for people who have actually bought and used your model so that they will give you a personal review before I would even think about buying it.

[Kevin]

I'm with Bruce on that one. That coin does not include installation or your time if you are the one doing the install. I am a fuel injection guy as I never learned carbs. I did do a swap from factory computer to a stand alone system on my car. You need all the sensors so that the computer can make the correct adjustments. The amount of tweaking you can do with a modern stand alone computer is rather complex.......way above my knowledge base. There are actually fuel maps for cold start vs hot start and you can even change the maps based on the voltage being supplied by the alternator. The timing can be programmed based on load and rpm and all sorts of crazy stuff. It has been two years since I even looked at the settings on my rig. I got it running safely based on wide band oxygen sensor that is built in to the down pipe and I walked away from it due to lack of time. The car has the power to break traction in third gear but there is so much more on the table with proper tuning. A car engine is limited duty and the boat is continuous duty.....two totally different animals as far as programming. I think I would steer away from that adventure unless you just enjoy a challenge.

[Bruce]

The nice thing about computer tuned systems that have end user adjustments is tuning the performance to your application. No two chassis builds are the same and neither are engines. You add tires, density altitude, pavement temp and a dozen other variables and having computer access is great.

The TBI after market system I worked with had no end user adjustments other than wide swings in curves using a reset switch and an led.

Carbs are easy. Got a friend who bought a 31 Packard with a straight 8. Called me over to ask what this thing was under the manifold pointing down.

Why that's an updraft carb, a what he said? Just chuckled.

[Pete Fallon]

Rawleigh,
I have factory installed TBI system in my 31 I installed them in late 1997 Big block 454 7.4 L Mercruisers with FWC and 8 degree Hurth down angle trannies. The reason I went with the TBI system was that the big blocks were boiling the fuel before it got to the injectors(MPI) They run strong and are very stingy on fuel. The electronic components are a nightmare, map sensors, ECM's, throttle sensors, temp sensors, trannie sensors, You name it there is a sensor for it. But when they run they are flawless. My factory direct engines were tuned to 310 hp and can be dialed up to 330 with a tweak of the computer. Like Bruce said they didn't last long in the marine application 1997 to 1998 just 2 years, parts are still available thru Merc or after market companies. I did have a few issues with back firing that would burn the wires on the injectors but I fixed it with some heat shield material. Anyway that was the way I went when I repowered from 440 Chryslers that I couldn't get parts for.
Pete Fallon

[Bruce]

Pete,
While all the marinizers basically used GM auto components for their systems including ECM's, Merc gave me the least amount of trouble. Crusaders were terrible as were others.

I don't think the programmers at GM understood marine engine loading. Unlike cars which very rarely go from idle to 3/4 throttle, thats common for marine. That throttle opening would dump manifold vaccum to 0 with a hugh rush of air. There was just enough delay in the electronics to introduce a real lean condition causing back firing since the injectors were mounted on above the intake just like a carb. That air fuel mixture then had to atomize and distribute down to each cylinder with those at far front and back always getting slightly leaner mixtures.
This is where timing is critical and needs to be tied into the ECM.

Another issue with marine is lack of 0'2 sensor measuring the exhaust gas for proper air /fuel and adjusting timing and fuel delivery. Other than a knock sensor to retard timing should it occur, TBI relied on a temp sensor and throttle position sensor for most of its monitoring.

Most marine intakes have uneven length runners adding to the problem.

This issue was fixed for the most part when they went to direct port injection and added a map sensor.