Nissan 70hp

"I have a 1997 nissan that sta

"I have a 1997 nissan that starts fine and idles okay, when I put it in gear and up to about half throttle everything is ok. When you go past half throttle it starts to have a bad vibration and seems to have a loss of momentum... any ideas?"

"Brian, new problem (ie, j

"Brian, new problem (ie, just recently happened)?

Did you happen to hit anything with the prop (maybe unbalanced it a bit), even just a sandy bottom????

I only ask because it's always best to start with the "easy answers"..."

"Thanks for responding, no the

"Thanks for responding, no the boat has been in the boat dock since the last time we had it out and it didn"t do anything like that before. Any other ideas???"

"Ok, most times when something

"Ok, most times when something like this happens after the "last time out running fine" it is fuel related.

But, to be sure it wouldn't hurt to check the spark at all cylinders when you notice this issue. If you can get ahold of a timing light and rig it up to watch when you notice the power loss, that could rule out (or include) an ignition problem.

With the new E10 fuels (those containing up to 10% ethanol, alcohol or metanol) your carb(s), filters, gas lines can be fine one day and clogged or gummed the next. The alcohol really cleans your system out, but does so by loosening every bit of crud/varnish stuck to your fuel system and clogging something when it does.

So I would check the easy stuff first - fuel pick-up in the tank, hose connections (could be extra air getting in), fuel filter, water separator (if equipped).

If all those are ok, and your ignition looked to be good, the high speed carb jets may be gummed or partially clogged - requiring a good cleaning..."