need help with 1995 7.4 BII (need an expert)

[captainzac]

tried to get help on another forum but they were not able to help
Ser. #0f557206
Problem
when I add power to get on plane ( but not every time ) the engine loses all power just like you pulled the plug or turned the bat. switch to off
it happens for a split second maybe 2 or 3 times and after that does not happen again
today I went to the boat and checked all conections (Elec) and cleaned them up
started the engine and when I brought the throttle up past 500 rpms it kicked into gear
after a few minutes I was able to rev. the throttle up as normal
then I noticed that if I had the blower on the amp meter would show a discharge at 11v and when I turner the blower off I got a charge of 13videas
Any

 

[26aftcab454]

Re: need help with 1995 7.4 BII (need an expert)

sorry-no expert but sounds like a short- a firing miss.i had the shop replace plugs- check and clean plug wires-all good- clean the distributor- runs like a champ now. it could be a short in anything that is connected to the distributor.

 

[captainzac]

Re: need help with 1995 7.4 BII (need an expert)

OKbut can you tell me should the amp meter show 11v with the blower on and 13 v with it off even at 1500 rpms

 

[180shabah]

Re: need help with 1995 7.4 BII (need an expert)

You blower should have minimal effect on the volt meter. You should have no problem running the blower, bilge pump, some lights, stereo, trim the drive, etc at the same time. Sounds like you have some corroded/weak connections in your electrical system and electronic ignitions don't like being deprived of voltage.

 

[captainzac]

Re: need help with 1995 7.4 BII (need an expert)

also you are making me think this through
when I add power to get on plane I always have the blower on until I get on plane
is there a chance that the alt. is not putting out enough power
I can try this out in the morning
but maybe someone knows if it would have any effect

 

[danond]

Re: need help with 1995 7.4 BII (need an expert)

You can eliminate (or include) the alternator by removing it and taking it in for a bench test.

Aside from that, get under the hood and clean every single electrical connection, then do the same back at the dash, and clean up the contacts on your ignition switch.

Do you own a volt meter? You shouldn't rely on your dash gauges. They're cheap and prone to failure and incorrect readings.

 

[180shabah]

Re: need help with 1995 7.4 BII (need an expert)

is there a chance that the alt. is not putting out enough power

Sure it's possible, test it. However, it is more likely that your connections are just plain old nasty.

 

[captainzac]

Re: need help with 1995 7.4 BII (need an expert)

Yes I have a meter
used it and the dash mounted meter might not be exact but shows the same drop
But does someome know if the engine requires a certain amount of volts to continue to run

 

[Anchor Management 1]

Re: need help with 1995 7.4 BII (need an expert)

If you have one,did you check the connections on the back of the battery switch.

 

[180shabah]

Re: need help with 1995 7.4 BII (need an expert)

But does someome know if the engine requires a certain amount of volts to continue to run

You need 12 volts in a 12v system. Different systems (like your ignition that I mentioned above) start failing between 11 and 11.5 volts.

 

[captainzac]

Re: need help with 1995 7.4 BII (need an expert)

thanks
but I checked the bat. switch all good
my boat is kept under a covered slip and stays very dry
not saying i have no corrosion but boat is kept very dry

 

[captainzac]

Re: need help with 1995 7.4 BII (need an expert)

lets think of this
in the morning if I get the boat on plane with the blower off and all elect load as low as posible and the eng.operates correctly then
is it the alt, or coil, or what

 

[180shabah]

Re: need help with 1995 7.4 BII (need an expert)

If you are convinced that the alternator is the problem, take it off and have it tested.

 

[flargin]

Re: need help with 1995 7.4 BII (need an expert)

I think there is a cutout voltage on the Thunderbolt ignition module, and if that is not well grounded you will loose everything really quickly

Your alternator may be the problem, your battery may as well if it is weak, it could be draining down the system, but you would likely find similar problems with starting, not just running.

I think you have to search for your lack of solid connection, I would try:
- main ground connection on the battery,
- Main positive,
- motor to boat connector, pull it apart and ensure there is no corrosion inside of there.
- Ignition coil connections

I did have a friend who had the same problem, but more random, and it was the motor to boat connector. needed so cleaning and di-electric grease.

 

[captainzac]

Re: need help with 1995 7.4 BII (need an expert)

Thanks
today I am going to clean the Boat to engine harness very good and apply dielectric grease. then I am going to first run the boat with the blower on if I still get the stopage then I will try it with the blower off if i still have the problem then I guess I will check the coil ( I do not think it has ever been changed) followed by the Alt.
I guess if I go from cheapest fix to most costly it might work out best since I cannot pinpoint the exact cause

Harry

 

[180shabah]

Re: need help with 1995 7.4 BII (need an expert)

Cleaning connections (ALL of them) is free.

 

[captainzac]

Re: need help with 1995 7.4 BII (need an expert)

OK guys

Heres what happened today
cleaned every connection and I could find (took 2 hrs)
started eng. with all elect. items off (it did not kick into gear and was able to advance throt. )
turned on blower on and got a drop in the voltage
turned on different elect. items and got a drop in voltage
took the boat out
got a reading of about 11v at 1000 rpms (no wake)
as I was getting the boat on plane volt. stayeed at 11v
after I got on plane the volt. got to 12.5
stopped
went to Bat 2 (House)
all numbers matched above numbers
note: checked bats. all with in limits
what do you think

 

[JustJason]

Re: need help with 1995 7.4 BII (need an expert)

check your alternator. Sounds like your not even charging.

 

[180shabah]

Re: need help with 1995 7.4 BII (need an expert)

Now that we have clean tight connections, we can move to components, and yes the first one will be the alternator. I would also have the batteries load tested. That is a pretty significant load drop when you turn on your 3-4amp blower.

Any auto parts store can test batteries and alternators (should do it for free). If you replace the alternator, just make sure you get a marine unit, we don't need another " boats really can explode" thread.

 

[captainzac]

Re: need help with 1995 7.4 BII (need an expert)

up date

A local shop here can test the Alt. I told them to go ahead and order the parts it will take to rebuild the Alt. but before they do that they can test to find out if the problem is the Alt.
even if the alt is good I am going to overhaul it just because of how hard it is to remove.
I will have an update Wed.

Harry