1996 mercury 75 hp carb?

jackd1023 · #1 October 17th, 2009, 10:19 AM

Hello and thanks in advance for your help.

I just purchased a used boat from a used car dealer(EBAY). The boat is an 1996 Spectrum 18' with a 1996? 75 hp 2 stroke 3 cyl merc. Only paid $1500 for boat motor and trailer.

They told me that they knew nothing about boats and the gentleman that traded it in said it ran, they however could not get it to start.

I got it home and noticed that the Run/stop switch on the controls were on the off position. I tried to drain the gas tank but it is and internal tank so I am not sure I got it all out. Filled tank with 93octane. I sprayed the crap out of the carbs and pulled and cleaned the plugs. Fired the second crank and ran great.

I then decided to go fishing. Cranked and started spitting water like a champ. I left the launch let it warm up then hammer down. Ran great for about a mile then it fell on its face. I could not get over 3000 RPM and had a nasty loss of torque. Idled great and ran fine till i throttled up. ran a compression test all in the 130 range.

Before I start replacing parts any ideas? I have seen high speed jets mentioned, where and how please. Also the black box (deck of cards) above carbs should I make extinct? My wife is already pissed I bought it (she does not recognize a deal) So if there is a cheap fix would help out my marriage lol. Thanks for the help

Laddies · #2 October 17th, 2009, 10:42 AM

It sounds like a plugged high speed which you can get to by removing the plugs on the port side of the float bowl to clean if you don't want to remove the carbs and clean them which would be the proper repair

jackd1023 · #3 October 17th, 2009, 10:47 AM

I plan on pulling carbs this winter was just hoping to get in a few fishing trips before the ice sets in. What about the black box? Thanks a lot

Laddies · #4 October 17th, 2009, 01:10 PM

They never had a idle stabalizer on the 3 cyl 90 that I have seen, it might be a rev limit. what color are the wires and where do they go, plus the serial number would help

jackd1023 · #5 October 24th, 2009, 03:12 PM

Thanks for the advice, I cleaned out the high speed jets blew them out and they looked clogged with what looked like 2 stroke oil. I have not water tested yet.

I noticed the black box for lack of a better term, that is on top of the carbs, the wires were burnt. I cleaned soldered and shrink wrapped them it did not seem to make much of a difference thou. Any idea what that is and maybe what would cause them to burn?

jackd1023 · #6 October 24th, 2009, 03:14 PM

I wrote down the serial # but have no clue where I put it, I believe that it started with OG could be wrong. I had it looked up at the marina to get spark plugs fuel filter etc.. I was told the engine was a late 96- early 97, if that helps

jackd1023 · #7 November 1st, 2009, 03:41 PM

OK the serial # is OG227090

I got the carbs off. I cleaned them there was a lot of black residue in the float bowls. I blew out all the jets cleaned and adjusted the floats.

I did notice when I was taking off the carbs there is a "black box" with a few wires coming off of it. 2 red 2 yellow and a few more . What is this box and what does it do. The wires coming off of them looked to be burned and when I took it off i noticed that the inside looked to be burned too. Some help would be appreciated.

I also replaced the fuel filters new plugs and new fuel line.

I am planning on reinstalling carbs tomorrow but would like to know what that black box is what it does and should I replace. Thanks in advance for your input.

Laddies · #8 November 1st, 2009, 04:40 PM

That sounds like the regulater, heres a parts list for you to check out and that engine does have a rev limiter on it. http://www.ishopmarine.com/ishop/jsp...ier-050-025-MM

bhile · #9 November 1st, 2009, 05:05 PM

Your motor is a 1995 model. That black box is your regulator/rectifier and if the wires are burnt there is a 99% chance it is shot. You should also rebuild the fuel pump while your at it. Be sure to replace the check valves with the new style. They come with the kits from merc.

jackd1023 · #10 November 1st, 2009, 05:56 PM

Laddies thanks for response, looks a lot more like the regulator than the switchbox. is there a way to test this or what could cause this to go bad?

jackd1023 · #11 November 1st, 2009, 05:57 PM

The book at the local marina said it was a late 96 early 97 model, does not really matter thou, what are the symptoms of a bad regulator?

Laddies · #12 November 1st, 2009, 06:15 PM

Here's the test.

Silvertip · #13 November 1st, 2009, 08:14 PM

There is an easier way to tell what year it is: look at the data plate on the left side of engine. Like this one:

jackd1023 · #14 November 1st, 2009, 10:16 PM

Thanks for all of your help, I will let you know the verdict.

jackd1023 · #15 November 3rd, 2009, 08:31 PM

Thanks again I did order the rectifier should take less than a week I hope. What are the symptoms of a bad rectifier? could this cause the initial problem of not getting over 2k RPM?

I did test it and it was/is bad Just would like to have an idea ifI have to put more money into this thing. Thanks again!!