1990 Bluewater 3.7 Guage Issue - not reading correctly - bouncing

[frankttaylor]

All,

Not sure if this is right place to post my latest issue. I have a 1990 Bluewater with 3.7 L Mercruiser. Boat sat for at least 7 years before she was re-surrected. When we got her unning in the driveway all the guages seemed to run perfect. I had on water this last weekend and when I was at no-wake speed the fuel guage dropped to empty, oil pressure to 5 -10lbs, the volt meter was bouncing as well as the temp guage. They seemed to smooth out and work properly when I picked up speed. I know the charging system on these creatures are a bit tempermental (from what I have read). Do you think it is a connection issue? Charging issue? The boat seems to run OK. - I also noticed the temp rose on the boat when I was cruising. It ran about 160 degrees which doesn't really cocern me and I attributed to warm lake water is this normal? I changed impeller and it is working excellent.

Thanks!

 

[generator12]

Re: 1990 Bluewater 3.7 Guage Issue - not reading correctly - bouncing

When you were in the driveway you were on muffs and running in neutral. Your idle was probably smoother and just a little higher RPM than when idling in gear at no wake speed.

Let's start with temperature. 160 degrees is just fine at cruise - in fact, it's just about perfect. Second, when fully warmed up and at very low speed (i.e., idle or close to it), 5 - 10 PSI oil is just fine. That too is normal as long as you see it increase when RPM increases. (Remember, the oil pump is running slower when RPM is down. As well, the oil viscosity is lower at normal temp. than when cold.) Some variation in indicated voltage is not unusual at idle - your RPM rate at idle may be just on the edge of what the alternator needs to provide charge. If that clears up immediately when the engine is throttled forward, consider it normal. Same for the oil pressure fluctuation.

Now the fuel gauge - that's a different matter. The sending unit is typically the problem here - either the connections at the sending unit are bad (i.e., corroded) or the unit itself is failing. It may read on scale part of the time and off scale the rest. You can replace it for about $30 if needed. It could be the gauge itself, but normally isn't.

 

[frankttaylor]

Re: 1990 Bluewater 3.7 Guage Issue - not reading correctly - bouncing

Generator12,

Thank you for your input. My concern was there wasn't enough charging to the system at low rpm. Everything seems OK. The last boat I ahd had an 18 gallon tank. This one has a 35. It is likely that the fuel guage is reading correctly and when I throttle the fuel is all coming to back of tank where the float is. It just fluctuates so much - that is my concern. I guess if I keep planty of gas in it.

Frank

 

[generator12]

Re: 1990 Bluewater 3.7 Guage Issue - not reading correctly - bouncing

Frank, lots of people on this forum describe the fuel gauge in a boat as something to tell you when you're full, empty, or "somewhere in between". Beyond that, accuracy cannot be counted on.

 

[frankttaylor]

Re: 1990 Bluewater 3.7 Guage Issue - not reading correctly - bouncing

Frank, lots of people on this forum describe the fuel gauge in a boat as something to tell you when you're full, empty, or "somewhere in between". Beyond that, accuracy cannot be counted on.

Fair enough

 

[fmalott]

Re: 1990 Bluewater 3.7 Guage Issue - not reading correctly - bouncing

i posted a month ago or so on this forum i had the same problem with my fuel gauge bouncing all over the place i tested the gauge according to test the gauge was fine i tested the fuel sending unit and that's is where the problem was the fuel sending unit just seen it's day my boat is a 1983 with a 470(3.7). so i replaced the fuel sending unit and now i have a new problem when i installed the fuel sending unit it pegged the gauge to full. i did hundreds of test and with no luck. so the next thing i did was buy a new fuel sending unit that came with a gauge hook everything up and problem solved. so take the advise from generator12 and buy the kit that has both gauge and fuel sending unit. BUT please do some test first before you spend money

 

[frankttaylor]

Re: 1990 Bluewater 3.7 Guage Issue - not reading correctly - bouncing

i posted a month ago or so on this forum i had the same problem with my fuel gauge bouncing all over the place i tested the gauge according to test the gauge was fine i tested the fuel sending unit and that's is where the problem was the fuel sending unit just seen it's day my boat is a 1983 with a 470(3.7). so i replaced the fuel sending unit and now i have a new problem when i installed the fuel sending unit it pegged the gauge to full. i did hundreds of test and with no luck. so the next thing i did was buy a new fuel sending unit that came with a gauge hook everything up and problem solved. so take the advise from generator12 and buy the kit that has both gauge and fuel sending unit. BUT please do some test first before you spend money

I appreciate the advice. Since it sounds like nothing to be concerned about, I will just live with it for the time being. I have heard more then one boat owner tell me not to trust the fuel guage. You would think in all the years that boats have been around they could have figured out a way to make them trust worthy.