Big Motor questions

Kentuck · Post by **Kentuck** » Tue Jul 24, 2012 10:49 am

Went out fishing last Saturday for the first time since March. I know, that 's bad! Anyway, while running around through out the day I noticed my big motor was "pulsing" in terms of power as I was going from spot to spot. By pulsing, I mean you could feel the boat speed up then slow down slighty. RPM's stayed the same. Have never noticed this before. Nothing real dramatic but I noticed it. Was using a fresh tank of gas. It's a Yamaha 150. Any thoughts on what it could be? Motor started and seemed to be running fine other wise.

whazup · Post by **whazup** » Tue Jul 24, 2012 11:13 am

Rough water?????

Kentuck · Post by **Kentuck** » Tue Jul 24, 2012 12:09 pm

My first thought was it was areas that had a lot of current changes, like eddies. I don't know, may have just been me, but I've never expereinced that in this boat.

Revoke36 · Post by **Revoke36** » Tue Jul 24, 2012 12:20 pm

Running through weeds maybe?

ash · Post by **ash** » Tue Jul 24, 2012 12:44 pm

First of all I would talk to a mechanic, Lou and Robert at A Boat Shop is who I use. Pull the prop to see if there is any tangles in the prop.

The other thing I would ask is have you had the fuel lines changed? Is your Bulb hard or going soft when this happens? It could be fuel, it could be that there is a blockage in the fuel line - if your not running stabil and leaving this ethanol bio fuel in the boat for that long it starts to seperate and do nasty things to the fuel lines. I know Robert has been replacing late model boat fuel lines when they arrive at the shop. - I wouldnt press this engine any further until you have identified what is causing the pulse.

mrbassin0614 · Post by **mrbassin0614** » Tue Jul 24, 2012 5:01 pm

Had the same prob with a 150 yam. check the plugs and make sure they are good. then another time it carbs needed cleaning

aNNieNsaLTIE · Post by **aNNieNsaLTIE** » Tue Jul 24, 2012 6:07 pm

ash wrote:First of all I would talk to a mechanic, Lou and Robert at A Boat Shop is who I use. Pull the prop to see if there is any tangles in the prop.

The other thing I would ask is have you had the fuel lines changed? Is your Bulb hard or going soft when this happens? It could be fuel, it could be that there is a blockage in the fuel line - if your not running stabil and leaving this ethanol bio fuel in the boat for that long it starts to seperate and do nasty things to the fuel lines. I know Robert has been replacing late model boat fuel lines when they arrive at the shop. - I wouldnt press this engine any further until you have identified what is causing the pulse.

I second with ash..... If you haven't changed your fuel lines, run some type of treatment, done a tune up in a while your going to have performance issues.
My friend had the same problem with my old boat. He never changed the main fuel lines or filter, no annual tune up, just ran it until he experienced a problem... I know money dosent grow on trees, but if you squeeze every trip out of your boat and avoid or postpone scheduled maintainence you may be stuck one day a long way from the ramp.

DeltaDan · Post by **DeltaDan** » Thu Jul 26, 2012 8:08 am

Kentuck wrote: I mean you could feel the boat speed up then slow down slighty. RPM's stayed the same. Have never noticed this before. Nothing real dramatic but I noticed it.

Monts - I am thinking Hub Slippage from your prop being out of the water for so long.

( not funny - I have another 72 hours of overtime on this next paycheck and I am plumb wore out. )

... When you say the RPM's dont change - Is that by site of your gauge -- or your ear ?

ash · Post by **ash** » Thu Jul 26, 2012 1:34 pm

Holy crap a Delta Dan sighting

Kentuck · Post by **Kentuck** » Thu Jul 26, 2012 3:01 pm

Thanks all. Never replaced fuel lines. 100 hour service last year. Brand new tank of gas (one tank was empty). Thinking about it I think I did hear the engine running slightly different, but RPM gauge never changed. Water pressure was good.

mrbassin0614 · Post by **mrbassin0614** » Fri Jul 27, 2012 4:25 am

Dude got same motor, had same problm twice. Once was spark plugs other time carbs needed cleaning.

chf8500 · Post by **chf8500** » Fri Jul 27, 2012 7:15 am

I had a 175 EFI was doing the same thing for about 3 months, did not think to much about it as it would always correct itself, untill about a quarter mile after blast off blew a piston, get it to a good mech and have him check it out lots of good advise on here but believe me that it can be very costly if you wait to long doing the trouble shooting yourself

Mike V.W. · Post by **Mike V.W.** » Fri Jul 27, 2012 7:54 am

We have seen a lot of those engines need the lift pumps changed they wear out and will leak fuel by and cause the engine to surge.

Mike Van Wagner
Gone Fishin Marine
1880 N Lincoln St.
Dixon Ca. 95620
707-678-1600

CN · Post by CN » Thu Aug 02, 2012 12:10 pm

chf8500 wrote:I had a 175 EFI was doing the same thing for about 3 months, did not think to much about it as it would always correct itself, untill about a quarter mile after blast off blew a piston, get it to a good mech and have him check it out lots of good advise on here but believe me that it can be very costly if you wait to long doing the trouble shooting yourself

Was that at the HBC up at Clear Lake?

Kentuck · Post by **Kentuck** » Wed Jun 19, 2013 1:56 pm

Just remembered to update this. Turns out two lift pumps were bad.

Jeff Jewell · Post by **Jeff Jewell** » Wed Jun 19, 2013 2:37 pm

Kentuck wrote:Just remembered to update this. Turns out two lift pumps were bad.

Same thing as mine..... I called Mike V.W.
Runs great now....

blkdog812 · Post by **blkdog812** » Wed Jun 19, 2013 3:47 pm

how old was the gas you let sit in your carbs? this ca fuel will cause issues if left sitting in your carbs. run some seafoam in the tank and see if that curses it.