sydneyACE
06-18-2012, 01:41 AM
Ok, so my boat has been really hard-starting (starter motor has lots of difficulty spinning it fast enough to fire), but I've just been dealing with it. Every once in a while, if the battery gets too low, it just wont turn over. We originally though the starter was going-out so I took that out and had it tested. It seemed to be working fine though. My brother who is a way better mechanic than I am suggested the timing was too far advanced which makes sense. So on Friday, in-preparation for this weekend, we put the timing-light on it and retarded the timing some. Worked like a charm. The boat started nice and easy, and the starter said "thank you". We ran it on the hose for a while and everything was looking good for Saturday.
Well, Saturday came and I got to the lake, launched the boat, and she fired right-up like a dream, on the first crank. I motored away from the dock and stopped to check under the cover to see that everything was alright. (I had just had the impeller go-out on the last outing so I was a little paranoid.) Sure-enough, I looked, and the pump wasn't drawing any water out of the lake and the manifolds were getting really hot. (I have clear hoses on the water system.)
Very discouraged, I tried checking everything I could think-of to get it to pump. It pumps ok when I disconnected the hoses running from the thermostat housing to the exhaust manifolds, but when I hook them back-up it stops pumping.
Long-story short, I tried everything I could think-of, checked everything I could think-of (obviously checked the impeller), and couldn't figure it out.
My genius brother (on a hunch) tried something though that fixed it. He advanced the ignition a little again. Bam! Intantly started pumping water again. I know it has something to do with exhaust back-pressure, but couldn't believe what a big difference a few degrees of timing can make. Cylinder pressures must still be high-enough when the exhaust valves start to open that it's creating lots of pressure in the exhaust system. (Which overwhelms the raw-water pump with lots of pressure in the exhaust manifold water-jackets, and stops the flow.)
Sorry for the wall of text. I seem to do that every time.
TL;DR: (summary)
My boat was very hard starting (cranked too slowly). Solution, retard the timing slightly.
Raw water pump not pumping enough to cool the exhaust or pick-up water from the lake. Solution, we advanced the ignition timing just a bit because we must have retarded it too much before. (Operator error on an adjustable timing light.)
**Has anyone else ever noticed how adjusting the timing affects the cooling flow? I was very surprised.**
Anyway, I'm just happy I got to get-out and have some fun today without toasting an impeller... even though it was windy most of the day...
I did get some pics for you all though. I will post them up soon!
Well, Saturday came and I got to the lake, launched the boat, and she fired right-up like a dream, on the first crank. I motored away from the dock and stopped to check under the cover to see that everything was alright. (I had just had the impeller go-out on the last outing so I was a little paranoid.) Sure-enough, I looked, and the pump wasn't drawing any water out of the lake and the manifolds were getting really hot. (I have clear hoses on the water system.)
Very discouraged, I tried checking everything I could think-of to get it to pump. It pumps ok when I disconnected the hoses running from the thermostat housing to the exhaust manifolds, but when I hook them back-up it stops pumping.
Long-story short, I tried everything I could think-of, checked everything I could think-of (obviously checked the impeller), and couldn't figure it out.
My genius brother (on a hunch) tried something though that fixed it. He advanced the ignition a little again. Bam! Intantly started pumping water again. I know it has something to do with exhaust back-pressure, but couldn't believe what a big difference a few degrees of timing can make. Cylinder pressures must still be high-enough when the exhaust valves start to open that it's creating lots of pressure in the exhaust system. (Which overwhelms the raw-water pump with lots of pressure in the exhaust manifold water-jackets, and stops the flow.)
Sorry for the wall of text. I seem to do that every time.
TL;DR: (summary)
My boat was very hard starting (cranked too slowly). Solution, retard the timing slightly.
Raw water pump not pumping enough to cool the exhaust or pick-up water from the lake. Solution, we advanced the ignition timing just a bit because we must have retarded it too much before. (Operator error on an adjustable timing light.)
**Has anyone else ever noticed how adjusting the timing affects the cooling flow? I was very surprised.**
Anyway, I'm just happy I got to get-out and have some fun today without toasting an impeller... even though it was windy most of the day...
I did get some pics for you all though. I will post them up soon!