78 30ft Sedan bridge Sea Ray Idle/slow issues? Electrical problem?

[acem77]

I have been helping my dad get his 78 30ft Sedan bridge Sea Ray up and running perfect.

Short story my day got sick and did not use his boat in 3 years.

After that it did not run good at all,
So I started to help him with the boat since I can crawl around and do the hard labor.
We replaced all the fuel, fuel lines, fuel filter, oil filter, fuel gauges.
Water pump, replaced the points with solid state devices, coils, batteries, spark plugs, spark plug cables,
Had the carburetors rebuilt.

Now the boat runs great while cool or at high rpms.
After it runs for while it will not idle or run slow.

This will happen to both engines at the same time. like clockwork it happens each test run.

The only thing common to each engine is the electrical system.

I took my multi meter with me this last time and did some readings.

The biggest thing I saw was when i took a reading from + side on the coil and - on the one battery.
While running the engine id see VDC10.20 to VDC8.50 depending on the rpms. Anything under VDC9 the engine would start to run worse until a stall around VDC8.70
the most i saw was around VDC10.40 when the engine was at 3/4 full throttle. Not sure on the rpms

Things I don’t understand.

1. I thought I should see 12vd. When reading from the + and the - on the coil.
I read 2-3VDC.

2. the coil had a label saying something about a resistor.
There is not one on there now, and my dad said there never was one.
Do the coils need a resistor?

I am going to guess I have a bad connection somewhere and when the boat heats up the resistance goes up messing with the electrical system.

Does anyone have any good advice.

Thanks

 

[kybishop]

My 1982 210 Cuddy was doing something very similar. It ran great cold, ran great throttled up but when idling or at idle speed it would just quit all the sudden. Turned out to be it was running ever so slightly hot. It had to do with the heat exchanger circulating pump I believe. The marine mechanic at our marina was diagnosing it and he replaced the circulating pump and I have had no problems since. The temp change was very slight but made all the difference. Not sure about the dual engine setup whether it could be the same thing, one circulating pump or both? He said they typically last 5 years anymore. Mine was 27 years old! They just get weak. Something to look into maybe.

Kevin

 

[kybishop]

Also, the mechanic said they run slightly cooler at higher rpms and running at idle speed increases the temp slightly and it just cuts out. He could tell by feel on the heat exchangers it was too hot. Mine would lope some then just quit all together. Took us a while to figure out what it was. Everything else was new or tested okay.

 

[acem77]

what about the voltage at the coil.

Another thing I forgot to mention.
If you turn on more electrical devices(blowers, bilge pump ect.) in the boat it will help cause the stall.

 

[SloppyJoe]

I can tell you on my 77 SRV300 that the electronic ignition does NOT tolerate low voltage well, such that starting both engines off one battery won't affect cranking much, but the voltage drop upon cranking the second motor can make the first motor stall.

However, if I parallel my start batteries I can easily start both then switch to one or the other battery for general ignition needs without problems.

Your problem is almost certainly electrical. I wonder if one or both alternators is failing to charge and maintain voltage while underway, hence the slow fade in the voltage.

? Slipping belt maybe OK at low speeds but slips at high speeds ? You should be able to isolate the amperage output of the alternators underway to determine if they are working properly.

You also may have a short in your house accessories that is draining power underway.

You need to isolate the starting/ignition circuits from everything house side, use quality batteries, and go from there. You might also replace the leads from alternator to starter/battery. If they are original you likely have excessively high resistance after 30+ years.

 

[acem77]

Last thing i did was remove one alternator so my dad can take it to get tested.
i heard some sqeaking from it "i think" at lower rpms near the end of the ride.
The was a rebuilt alternator, the other engine still has the original.

does a twin engine boat share electricity from both alternators to each engine?

Also should i read 12VDC at the coil contact while the engine is running?
i get 2-3vdc. form - and + on the coil, 8.70-10vcd from the coil + to battery -
Does the coil need the resistor?


The batteries are all new. from what my dad said some of the best you can get rating wise.

 

[kybishop]

Sorry could not help with the low voltage question. I will talk to our local marine mechanic and see what he thinks. He is very knowledgeable and has years of experience. Still may check the age and condition of the cirulating pumps if you are running a bit hot. I will see what I can find out about your voltage issues.

Kevin

 

[stevea661]

I have been helping my dad get his 78 30ft Sedan bridge Sea Ray up and running perfect.

Short story my day got sick and did not use his boat in 3 years.

After that it did not run good at all,
So I started to help him with the boat since I can crawl around and do the hard labor.
We replaced all the fuel, fuel lines, fuel filter, oil filter, fuel gauges.
Water pump, replaced the points with solid state devices, coils, batteries, spark plugs, spark plug cables,
Had the carburetors rebuilt.

Now the boat runs great while cool or at high rpms.
After it runs for while it will not idle or run slow.

This will happen to both engines at the same time. like clockwork it happens each test run.

The only thing common to each engine is the electrical system.

I took my multi meter with me this last time and did some readings.

The biggest thing I saw was when i took a reading from + side on the coil and - on the one battery.
While running the engine id see VDC10.20 to VDC8.50 depending on the rpms. Anything under VDC9 the engine would start to run worse until a stall around VDC8.70
the most i saw was around VDC10.40 when the engine was at 3/4 full throttle. Not sure on the rpms

Things I don’t understand.

1. I thought I should see 12vd. When reading from the + and the - on the coil.
I read 2-3VDC.

2. the coil had a label saying something about a resistor.
There is not one on there now, and my dad said there never was one.
Do the coils need a resistor?

I am going to guess I have a bad connection somewhere and when the boat heats up the resistance goes up messing with the electrical system.

Does anyone have any good advice.

Thanks

It doesn't always have a ballest resistor on the positive lead to the coil. I have an omc and the wiring diagram calls out a resistor wire. It just looks like a regular wire to me but I guess it has some resistance through it.

 

[acem77]

Sorry could not help with the low voltage question. I will talk to our local marine mechanic and see what he thinks. He is very knowledgeable and has years of experience. Still may check the age and condition of the cirulating pumps if you are running a bit hot. I will see what I can find out about your voltage issues.

Kevin

Great thanks.
ill mentions the circulating pump thing to him.