1980 175 hp v-6 3000 rpm

[Coloradolakeboy]

I live in Colorado and the elevation where I boat varies from 5000 ft to 9000 ft. Since the carb and fuel pump rebuilds and re-jetting for high altitude, I am only getting 3000 RPM and bogging under load (Tubers). Full Throttle RPM range 5300-5800. Once planed out and motor trimmed occasionally 5000 RPM . Idle is fine. Starts well, except on Ramp! Carbs and Fuel Pump rebuilt and new lines and bulb, Ignition test out good. Compression tested 120-125 with #6 at 115 at our 5000 ft. elevation. A local Mercury mechanic tested 15000 volts on plug wires and did the Link and Sync. He said the ignition was fine. I've got a 14.5 x 17 prop on it. Is this a fuel side problem or what? Thanks.
Rob

Edit: The tach was acting goofy last time out. Got Stuck at 5000 RPM.

 

[j_martin]

Re: 1980 175 hp v-6 3000 rpm

Just for grins and giggles, disconnect and tape off the yellow wires from the stator to the rectifier. Would bet the rectifier shorted and is causing trouble on the ignition side.

You should test the rectifier by the FAQ on this site, and also test for stator output to the switchboxes with a DVA. That might show up a weak stator or switchbox.

hope it helps
John

 

[Coloradolakeboy]

Re: 1980 175 hp v-6 3000 rpm

Are you saying to disconnect and tape the yellow wires and put it on the lake? It runs fine on the muffs and at low idle on the lake. John thanks again for your help, I will do the testing and report back.

 

[j_martin]

Re: 1980 175 hp v-6 3000 rpm

Yes, that's what I said.

The engine will run "fine" on the muffs on 2 cylinders. There is absolutely no load on it. In the water with a propeller is another story altogether.

That's why, even if one whole bank is missing at high speed, it will seem to rev of the top readilly on the muffs, and hit the wall at about 3000 on the water.

Tach runs off the charging system. Goofy usually means a bad rectifier. If running without it (just a test you see) seems to fix the ignition problem, then just replacing the faulty rectifier might be all you need. If not, you need the dVA to check if a stator or switchbox is failing.

hope it helps
John

 

[Coloradolakeboy]

Re: 1980 175 hp v-6 3000 rpm

I tested the rectifier per the FAQ directions on this site. The rectifier is bad. I also found that the two yellow wires from the rectifier to the stator had no insulation on them for the first couple inches. They were in contact with each other. Hope that didn't damage the stator. The ohm reading on the two yellow wires was close to spec. .85 instead of .75 I found a DVA adapter on www.Usatoolwarehouse.com for 25 bucks thanks to a comment on a thread by sparkieboat.

 

[j_martin]

Re: 1980 175 hp v-6 3000 rpm

Shorting the yellow wires theoretically shouldn't hurt anything, but if the insulation is that bad, how is the rest of the stator?

 

[Coloradolakeboy]

Re: 1980 175 hp v-6 3000 rpm

I only cut the black shrink wrap til the crumbling stopped and liquid taped the wires.

 

[Coloradolakeboy]

Re: 1980 175 hp v-6 3000 rpm

Update. I replaced the stator and took it to the lake this last weekend. It now has full rpm WOT and a good hole shot. The new problem is after a WOT run it loses power like it is running out of gas. I pulled back the throttle and hand a helper pump the primer bulb, it was not firm, but after doing so, the full rpm range could be achieved. So what could that be? I put a new quicksilver bulb on last summer.