Re: Nissan 40 HP problem
Re: Nissan 40 HP problem
DuckMarshal said:
I've had it in the shop three times already and can't get it fixed. It started out bogging down like there was trash in the carbs. Now it will only run about 7-8 MPH on the GPS and won't even get up on plane. The first mechanic I took it to cleaned the carbs and did some other stuff to it like raising the motor and changing my props out. Nothing worked and I'm out $600. The motor is in like new condition and is a 2002 40 horse. I heard that there is/was a problem with this model motor in the fuel system? Is that true?
Thanks.
Test a bit. Something will have an effect. Engine needs fuel, spark, air.
Fuel - Eliminate the simple things first - buy a small plastic tank a new fuel hose put brand new gas in the tank and try running from that tank. If 2 stroke motor needs premix 50:1, use a good TCW3 outboard motor oil (Mercury, Johnson, etc. ) *not* Pennziol, Quaker State, crankcase oil, chain saw oil, 16:1 or 32:1 chain saw mix, not last years gas, not gas you bought 4 weeks ago for the lawn mower. Gasahol (10% ethanol) is nation wide now. After 4 weeks, a vented can is 15% water. You can separate it by skimming off the gas, but the recovered fuel can be quirky by itself, so I use it 1 quart per gallon of fresh fuel.
Ok - on to the good stuff...
Use the choke for 10s when wide open throttle not on plane, it *should* kill the engine - if it helps it instead then it is fuel starved. If no change, check the choke. Same wide open conditions, but this time squeeze the primer ball for 20s - if that helps, you're not getting fuel into the engine, if that hurts then the carb isn't cloing its inlet valve when its full... Check for bad carb float, inlet valve or seat, or simple misadjustment of float height. Clean/replace all fuel filters. Check fuel hose/connections - hose hard? hose spongy? hose casing has cracks? Connections clean and tight? Connectors snap together and apart convincingly? - engine off, the squeeze primer ball any leaks?When primed the ball should be HARD, if its spongy, there is a fuel/air mix in the lines, that's a suction leak, replace lines and connectors. Does ball inflate s-l-o-w-l-y between sqqueezes? - hose collapses and/or fuel tank pickup is clogged cleand and replace things until it works right. Check fuel pump pressure and delivery - gauge is cheap, but see service manual, don't just pull off the spark plug wires for all engines anymore it can ruin the electronic ignition module. And don't spray fuel around, it tastes lousy. Poor delivery? Use different or replace fuel hose before rebuilding fuel pump, bad hose may collapse in suction, can't test with primer ball. Use different gas. Disassemble carb(s) and really clean all passages, when assembled use rubber sealant over screw plugs.
Spark - is the spark advance linkage connected? Wires look bad ? if they look good but a little WD40 helps, they stink. Spark plugs... too cheap to diagnose, just replace them with recommended - check the gaps. Check the routing and the wires from the flywheel coils to the ignition pack, and the ignition pack to coil(s). Check to see if other sensors are disconnected or borken and the motor is in cripple mode. (If it thinks its in reverse, out of oil, or overheated etc, it may be de-tuning the spark to protect the engine. Is it peeing (cooling water)? Check shift linkage to see if reverse power restrictor remains engaged in forward. Other sensors/conditions depend on engine type/model.
Air - There's no air filter... check compression. Less than 125 lbs? Maybe sticky rings - try Seafoam carbon remover engine cleaner. Try Seafoam "Deep Creep" spray from auto parts store, follow can directions. If there is an impressive white cloud for more than a few seconds on restart, run for 5 minutes and repeat the cleaning until there isn't, or 4 cleanings, or you used up the whole can. Retest compression - still poor? - head gasket? - 2 stroke crankcase sealed? bad reeds? - 4 stroke - burned valves? Not a mechanic? use the seafoam and see if it helps. It usually ruins the spark plugs, buy new ones and change them when you finish. If you are a packrat, you can put in old ones before you use the seafoam.
If all else fails try to trade it in to a Tohatsu dealer. When they check it and find it lacking they might tell you whats wrong... but don't fix it, just trade it in. Summer is short and you've already lost 1/2 of it to this motor.
