"anon-e-moose" wrote in message
...
Tim wrote:
On Mar 21, 6:11 pm, Ted wrote:
On Mar 19, 11:29 pm, jps wrote:



On Fri, 19 Mar 2010 19:07:50 -0700 (PDT), Ted
wrote:
Hi All,
I have a 3.7 Mercuriser Inline 4cyl motor and have noticed an odd
behavior with it. When at the dock or on the trailer with a cold
motor, it will crank and start right up, but when the motor is fully
warmed up it often doesn't want to crank. I've read of others wth
this motor who get vapor lock in a hot engine but I'm assuming these
folks at least get it to crank, whereas mine won't even crank. I
think I hear the click of the solonoid trying to engage when turning
the key and that's all. Vapor lock doesn't prevent the engine from
cranking does it? If I remove the engine cover and allow it to cool
for a while, it usually cranks and starts right up. The cooling
system is closed so the temp sits at 120-140f max. I installed an
electronic ignition kit about 7 years ago and other than that the
motor is stock. Boat runs great once it starts.
Thanks,
Ted
If you're for sure hearing the solenoid and the battery is good, what
about the starter motor? It'd be interesting to see if it'll crank
over when hot using a manual starter switch. Maybe needs a rebuild or
replacement?- Hide quoted text -
- Show quoted text -
thanks Tim and JPS,

Yes it's a 1986 motor. The 3.7 is a concoction (sp?) that Mercruiser
came up with (same as a 165 and 470 I think) that is a Ford 460 7.4
liter cut in half then fitted out with a cam driven alternator and
water pump amongst other oddities. Only reason I didn't initially
think of the battery being bad is that once the motor cools down a bit
it will fire up easily. I acutally have a Perko dual battery system
on it to be sure it gets good amps when starting.

Regarding using the starter switch, could I fudge it by cliping one
lead of large jumper cables to hot terminal and then grounding the
other lead right from the battery to see if it spins up or does the
starter switch just bypass the keyswitch and sends voltage to the
starter relay to close the circuit and thus pull power thru the
regular battery cables?

Being a marine starter I'll definitely have to remove it to inspect
the inside for corrosion (sealed to arrest any sparks). It's still a
bit cold up here in Pennsylvania so I probably won't be testing it for
a month or two. I'll post back when I find out more.

Thanks again for the suggestions,
Ted

OK, another question. If you know, is it a Prestolite or a delco
starter? The Prestolite has a separate solenoid that may or may bot
be mounted to the starter motor. Out of the starter field casing there
is a battery stud that either connects to the cable which leads to the
solonoid switch or if the switch is mounted on the field casing it's
connected to the stud with a flat copper strap.

The Delco version would have the solonoid attached to the starters
drive end housing with a small screw attaching the electrical contact
of the solenoid to the field strap.

one thing you can do first is to make sure all connections are in a
fine, non-corroded or 'hot' condition. bad connections make for bad
starts.

If it cranks in 'like new' condition, that is WHEN it cranks, I'd be
suspect of the battery or a 'hot' or loose connection.

Hope that helps
Just something to add to Tim's suggestions.
Sometimes the contact disk in the starter solenoid burns and makes bad
contact. Or the starter drive might stick and prevent the solenoid from
making contact. Sometimes repeatedly turning the key gets the disk to turn
to a clean spot. This is a common springtime problem. Hot connection is
good way to find a bad or loose connection. Just feel around. One bad
connection this method wont check out though is the physical ground
connection between the starter and flywheel housing, especially if the
flywheel housing is aluminum.

Years ago, some of the GM starters woiuld drain the battery when trying to
start hot. The gaps between the armature pieces would get partial shorts.
You could clean out the gaps with a hacksaw blade and they worked fine after
that.