1994 EFI Replacement

[Dan30]

Hi all, I bought a 94 Ski Nautique last fall knowing that the PCM EFI was first-generation and no longer supported by PCM. It runs very rich, and have been told that not much can be done about it. It accelerates very well, but hesitates at maybe 1200 to 1500rpm but then the power surges smoothly after that. The timing was set at 16 deg and my mechanic brought it down to10 deg because he thought it would help the hesitation; this was not helpful as now I still have the hesitation but lack power both before and after the hesitation. We exclusively use the boat for course skiing and want as much power as is practical. The boat has 330hrs after reportedly having the block cracked from freezing, total boat hours supposed to be around 650.

My questions are:
1. Is there a good after-market throttle body fuel injection system that I could install, or could I put a newer PCM system on? My mechanic is skeptical of after-market EFI as he has not had good experience with them for cars.
2. Should I just put a 4bbl Holly on it and be done?
3. Where can I find an engine specification sheet? I'd like to check the compression before I spend some money on this.

Thanks - anything helps!

[NautiqueJeff]

Engine spec sheet can be found here.

https://www.planetnautique.com/Corre...T-40Manual.pdf

Is this an early GT40?

[Peter6000]

Hi all, I bought a 94 Ski Nautique last fall knowing that the PCM EFI was first-generation and no longer supported by PCM. It runs very rich, and have been told that not much can be done about it. It accelerates very well, but hesitates at maybe 1200 to 1500rpm but then the power surges smoothly after that. The timing was set at 16 deg and my mechanic brought it down to10 deg because he thought it would help the hesitation; this was not helpful as now I still have the hesitation but lack power both before and after the hesitation. We exclusively use the boat for course skiing and want as much power as is practical. The boat has 330hrs after reportedly having the block cracked from freezing, total boat hours supposed to be around 650.

My questions are:
1. Is there a good after-market throttle body fuel injection system that I could install, or could I put a newer PCM system on? My mechanic is skeptical of after-market EFI as he has not had good experience with them for cars.
2. Should I just put a 4bbl Holly on it and be done?
3. Where can I find an engine specification sheet? I'd like to check the compression before I spend some money on this.

Thanks - anything helps!

Is this a gt40 with multipoint injection?

Sent from my SM-G892A using Tapatalk

[bradb]

I replaced my Pro-Tec ignition and throttle body injection with a Holley Sniper TBI kit.
After 1 season I’m more than happy with the results.
I’m happy to answer any questions you have about it.

Alternatively, I just posted a complete original TBI system with Pro Tec ignition for sale - including coils, ecu, sensors, trigger, wiring harness, etc. Hit me up if you are looking for spare parts.

I believe all the original systems were tuned to run rich.

Good luck getting it sorted
Brad

[gary s]

No mpi was not until 95. To the OP think Quick Fuel carb and D.U.I. distributor

[Jonny Quest]

Dan

I had a 1994 with the ProTec and throttle-body electronic fuel injection. At first, TB-EFI started acting up. I contacted Holley to buy a replacement injector. No dice. Holley informed me that all parts for that particular TB-EFI were no longer available (NLA). So, I started looking at after-market options for EFI. Not long after that, the ProTec completely died. I had to be towed back to the marina as the ignition system was completely dead. I contacted PCM about parts for the ProTec system...again NLA. When I started evaluating my options, I decided to go retro-fit back to carb and distributor. I went with a Davis Unified Ignition (DUI) from www.PerformanceDistributors.com and a QuickFuel marine carburetor. The retro-fit was not too difficult. The results were outstanding…almost equaling how the engine performed new. Send me a Private Message if you want additional detailed info.

JQ

[Dan30]

Thank you all for your replies. Yes, it is the GT-40. I was looking last night and saw the Holley Sniper EFI, and it looked pretty good. What all did you replace besides the TB? My fuel supply system takes 4 to 5 cycles to get fuel to the TBI, so I'm thinking to replace that as well.

Thanks!

[bradb]

Dan,
When most people refer to the GT-40 engine, they are referring to the multi port fuel injected engine released in ‘95. A ‘94 can have the GT-40 heads, but would be throttle body injected, and most people would refer to this as the “Pro-Boss”.

If you are looking to convert from a “pro-boss” to a Holley sniper, I can certainly answer a bunch of questions for you. From a GT-40, not so much!

So, assuming you are converting from a throttle body injection pro-boss, I replaced the whole fuel system from the tank forward, the whole ignition to the hyperspark dizzy, and of course the throttle body.

There were a few little things on the install that took a bit of figuring though….

I had a machine shop make me a spacer for the O2 sensor. I gave them my exhaust riser gasket and told them what I needed. They did a great job, even slanting O2 hole downwards as specified in the Holley manual.

The throttle body was wider than my old setup so I had to fab up a new throttle cable mount. The linkage was a different ratio (different distance from the pivot to the throttle cable connection), so I made up something for that too.

I replaced the ProTec ignition with the sniper Hyperspark too, so I had to get new plug wires (they used to go from the coils at the back, now they come from the dizzy at the front). I used GT40 wires.

A few other miscellaneous items that were a little tricky to source - the longer bolts for the exhaust risers I think they were 6.25” so I had to cut down 6.5” bolts (also hard to find in a store). I had to buy longer 4” exhaust hose after I moved the risers up with the spacer. It was pricey ~100$.

Honestly, the next hardest part was untangling and decoding the old wiring to remove the old system!!

I took a bunch of pictures along the way, so let me know if you have any questions.

[PaulM]

Brad,
I saw your post in this thread " 1994 EFI Replacement" and I'm interested in doing similar to convert to Holly Sniper. I think I know what to get, but you mentioned the disconnect of the old stuff was a chore. You also stated you had pictures and that could help. My 94 SNOB was running great until this season and now it spraying lots of fuel outside of the flame arrestor. I think the ECM is not controlling the injectors correctly and since getting parts are impossible I thought I would do a convert. One question ... did you consider keeping the old fuel pumps ? And info or help would be appreciated.
Thanks in advance,
PaulM

[Jonny Quest]

I had a 1994 SNOB that had the EFI fail. I went with a retro-mod and installed a QuickFuel M-650 carb and new electronic distributor. Results were amazing. The engine ran super strong.

JQ

[bradb]

PaulM, Disconnecting the old stuff wasn't hard at all, just time consuming to undo all the electrical tape and loom, etc so I could see what was going where.
If I remember correctly (and it was about 3 years ago now...), almost all the old wiring came off (and all the sensors), except for the alternator wiring and the harness up to the dash.

I did consider keeping the old fuel pumps, but 2 things made me change my mind. 1) I believe they were original from '94, so it was time, and 2) I couldn't find the specs of the high pressure pump to know if it met the requirements of the Sniper system. I did like the original setup, but have not had any issues with the single high pressure pump mounted below the floor where the fuel filter used to be. I also considered in-tank, but left that project for another day!

The pic below shows the general layout of what I did (before I did the wiring and dizzy, etc). It worked great, but I'm considering changing where I have the coil mounted. As it stands now, I can use "GT40" plug wires, except the coil wire is too short. it would be nice to be able to use the standard plug wires.

I do have a bunch of pictures I can share if need be. Pop me a PM with your email and I can send them along.

If you do go this route, post your progress. I'd love to see how it comes along.

[bradb]

PaulM, Note, I had them make me 2 spacers, but only one is threaded for the O2 sensor. I just wanted the exhaust risers to look the same on both sides (height).

Other tricky parts:
- had to fab up a new throttle cable mount out of angle iron. If I remember correctly this was because the new throttle body was wider then the original. It took a drill, grinder and an hour time.
- made an "extension" for where the throttle cable mounts to the throttle body. I later found that you could buy this part, but it wasn't hard to make.
- had to trim down the bottom mounting flange of my spark arrestor about 3/16ths in order for the doghouse to close.

- and a bonus tip - if you happen to drop anything down the exhaust manifold (like say the plastic cover for the o2 sensor), tape a straw to the end of your shop-vac... Don't ask me how I know... I spent 2 hours trying to fish it out various ways and was almost ready to order a new gasket and just remove the manifold when I thought of the shop vac idea! once I did that it was out in 2 seconds flat!!!

It should be clear by now that i'm not all that mechanical, and I managed to get through it! Good luck if you decide to give it a try, and If you have any questions, don't hesitate to ask.

[PaulM]

Brad and Jonny - thanks for your feedback and info. I was very interested in going with the Holley Sniper, but with all you, Brad, went thru to get it done scared me to attempted it. I decided to do the skidim retro carb approach, but I did a DUI distributor for the spark. I ordered all the parts and within start to finish, I have the boat back in service within in 2 weeks It's running the best I can remember, which is what I wanted during ski season. Brad I really didn't want to go back to "old school" however it just felt like I was going to spend some time doing what you did ... if was off season, I might have done the Sniper. However thanks for your pics and info as it did help me make my decision. Knowledge is king !! THANKS