errol_white
Recruit
- Joined
- Aug 31, 2003
- Messages
- 5
This 1987 outboard has worked reliably for years-20 to 30 hours per year. Then, first day out this summer I was tooling along ~4000 RPM and then sudden loss of speed. No buzzers, no yellow or green lights. I push the remote up and anything over 3200 generates a hollow running sound with the occasional rev up a few hundred RPM and right back down to 3200 RPM. Very smooth from 0 to 3200 RPM. Almost seems like there is a governor at work. Here is what I've done so far, on the weekends I visit the home that has the boat, and none of it has helped:<br /><br />Fuel:<br />A) Checked fuel filter and plastic screen that is closer in-line to the engine. Squeeze bulb and no difference while running. Replaced fuel pump. Ran off separate tank from hose disconnected at engine-side of bulb. No difference.<br />B) Bought manual. Rebuilt the two Nikki carbs. No sign of clogged jets, dirt, or water. Slightly re-adjusted linkages.<br />C) Checked plugs. All the same. All wet, and a little black looking but with short engine runs this is inconclusive.<br /><br />Mechanical:<br />A) Throttle cables not stretched, or slipped.<br />B) Checked all linkages. Nothing seems to have moved.<br />C) Compression check: All 4 cylinders within range of each other, and held pressure. I think all were around 140 psi, but don't have notes handy.<br /><br />Electrical:<br />A) Checked wiring. Looks OK. Connections tight, grounds secure.<br />B) Checked timing with timing light and manual. Minor adjustments. Mechanical timing does advance at higher RPM, so looks OK.<br />C) Performed resistance check of regulator/rectifier. Looked OK.<br />D) Performed resistance check of light coil. Looked OK.<br />E) Performed resistance check of high and low sides of all 4 ignition coils. Looked OK.<br />F) Performed resistance check of CDI, and most measurements don't match book. Not sure if this points to CDI problem, after all the engine runs great up to 3200 RPM.<br />G) CDI has blue wire coming from within the CDI that connect to CDI terminal "over-rev". Thinking that this part of CDI might be bad, I disconnected it. No difference. 3200 RPM max.<br />H) Checked 2 temperature sensor switches. Both are open-circuit-like they should be.<br />I) Shorted 2 wires for each sensor and caused remote buzzer to sound. This confirmed wiring to the temp sensors and the buzzer.<br /><br />This one's got me stumped. I'm now at the end of the season, and getting ready to pull the boat out and drop off at a Yamaha repair place.<br />Before I do that, do any of you have any other ideas?