91 Nautique ProTec???'s

My 91 Nautique hasn't been running good for the last few years and I am thinking it may be in part to a failing PCM ProTec system, any suggestions would be greatly appreciated...

For the last few years I have been struggling with this issue where my boat will start, idle, and run fine until I put it under load while pulling a skier or accelerate to over 2400 RPM. If I do either it the engine will start missing and not want to accelerate past that speed. If I back the throttle down it will run fine running at 2-2300RPM all day long with no misfiring. I am getting close to my wits end on this one.

I've replaced the plugs, multiple times along with wires. Also, have been running Seafoam and Startron w/fuel for the last 3 years with mixed results.

My thoughts are the ignintion is starting to go bad if it's the coils or whatever...any input would be greatly appreciated!!!

89Martinique wrote: Seafoam=Bad. Just for future reference. Your problem lies with your Oil Pressure Switch, not sender, and temp switch, again, not the sender. Had the same problem with my 92 Comp. Replaced the oil switch, all is good.

Like most of us, I'm on here to learn...

1. Oil pressure switch and temp switch... can you explain this; assume I know nothing about it (pretty close to the truth).

2. Seafoam=Bad. Hmmmm. I've always run Sta-Bil (lately the marine version for the ethanol garbage) in my boat gas (I've had a Mercruiser for 15 years and just got the 1984 SN2001 this year), and I used to add CD-2 Lead Substitute. I always run premium (hi octane). Now the CD-2 isn't available, so I've been using the small bottles from Gunk but they're a ripoff. So I've been talking to a lot of mechanic-types, and many of them have told me to just use Seafoam in the gas, and skip the Sta-bil and lead substitute. They claim the Seafoam lubricates the valves (I've heard that) and stabilizes the gas (I've never heard that before this year). So they sort of had me convinced... where are they going wrong?

I'm not trying to hijack the thread... the OP talked about using Seafoam.

kylem428 wrote: ...... other sign being that the boat runs like crap above 2.4k. Kyle

The conversion is the Viagra for the "Limp Mode" in the failing Pro-Tecs. Ha!

Thanks for the info guys, I appreciate it! I'll keep in mind the Seafoam info, I only used it as a fuel additive.

I was thinking it is probably time to do the conversion over to a distributor ignition system. I think I am going to probably try the oil pressure switch first and go from there, the temp switch is brand new w/less than 1 hour on it. Won't be able to give a report back til I get up north this weekend though.

One other question...I noticed when I was looking in my PCM manual tonight and it mentioned to disconnect the knock sensor when adjusting the idle or timing as that may cause it to go into limp mode as well, anyone know about this??

Jeff

If you ditch your Pro tec, I will take it off your hands. Would like a spare to tear into. Also, there are 2 Temp units on the intake manifold, one for dash, other for protec, replace the one for the protec. Above the oil filter there are 2 oil units, a big canister for the dash, and a small one for the protec. Replace both protec units and it should work fine. Post pics, will help greatly.

89Martinique...if I do ditch the ProTec I'll let you know. I ordered a new oil pressure switch, that hopefully I'll be able to install tomorrow evening. I'll try and post some photos this weekend too. I still have yet to get up north to work on it but the parts have arrived. I'm hoping to remedy this without going the retrofit route but that remains to be seen.

desertskier...I appreciate the feedback and will definitely check the voltage from the dash to the coils. My dash does goofy stuff if I turn the nav lights on so that could definitely be a culprit as well. I'll let you know what I find.

I ran my engine (on the lake under load) with the oil pressure switch and the water temp switch disconnected and the engine ran with no problems. I measured the resistance of each switch to ground and they are both open. So when a failure occurs (either low oil pressure or high water temp) the switch grounds the input to the protec which puts it into limp mode. If you suspect you have a bad switch just disconnect them and if the problem goes away then re-connect one at a time until the problem comes back. If you still have the problem with the switches disconnected then it is not caused by the switches. I didn't mess with the knock sensor but it's probably the same.

Well, if you get your dash gauges working you dont *Need* the switches hooked up. I mean the retro fit just bypasses them, no different than leaving them disconnected.