Engine tries to die, misses very badly once warm

[89Mariah351]

I got a used 89 Supra with a PCM 351 with 300 hrs last year. It ran super all summer.
This year I've only had it out 3 times and in each case, it starts fine, but after running it for like 20 or 30 minutes it starts dying out on me and missing and bucking like crazy.
Oddly, I found if I push the blower button in, it will make it stop dying out on me, but it doesn't stop all the missing and bucking. The voltmeter says 14v whether it's running fine or dying/acting up. When I push the blower in it says just above 12v if that's any help. I really appreciate your help with this, Thanks..

[89Mariah351]

forgot to say it's an 89 Mariah,
Thanks..

[selle92]

I just bought a 91 Mariah, and like you, after I've had her out, if it sits for 30mins- a few hours, it doesn't always start up right away. if I open up the doghouse, and let more air get at the engine, it usually kicks over. that or I have to take off the carb cover and that does it.

might try running the blowers longer before the 2nd start, and open up the doghouse when doing so.

could be the air cleaners dirty or plugged. Might replace that?- I'm still learning as I go too.

J

[Salty87]

have you done a tune up?
how old is the gas?
do you have a water separating gas filter?

if you haven't tuned her up yet, i would. that should be done annually or more often and definitely when buying someone else's old boat...unless they have great maintenance papers and had one done recently.

old gas could also cause those symptoms. you should also have a water separator filter, change it if you do (should be changed each year also). if too much junk gets to your carb, it could also need some work.

www.skidim.com has most of the parts your boat will need.

good luck and report back!

[Salty87]

selle...

yours sounds more like you've got too much resistance in your starting system when things get hot. have you checked that all of your battery and starter cables are in good shape, securely connected to their respective posts, and that your battery is holding a full charge? it is also possible that your coil is going....done your 'new' boat tune up?

you might want to start your own thread...

good luck and let us know how it goes

[89Mariah351]

Thanks for taking time out in your days to help me and others out, that's very kind of you all here..

selle,
I have just cleaned the air filter out about a month ago, so that's not it.
and it's been dying out and missing like crazy when it's warmed up and running.
Now that you mention it though, if it does die out when acting up when warmed up, it has a very hard time starting again.. unless I push the blower switch in for some reason, then it will start up again..hehehe

salty,
I have done a light form of tune up, at least the general maintenance kind that I know how to, like I have changed the plugs, cleaned the air "filter", changed the oil and looked in the distributer to see if I had points but it has an electronic ignition module in it. The cap and rotor look fine. I was thinking about changing them anyway along with new sp wires and maybe a new coil.. the coil that's on there looks kind of new though.
Last year I replaced the resistor because someone had it bypassed for some reason when I bought it. The gas is 1/2 old and 1/2 new from this year. I did put "sea foam"
stabilizer in it though. I don't honestly know if I have a water seperating gas filter on it to tell the truth.. it's the one it came with, I haven't replaced it yet. Is there any way that bad gas in the tank could make the engine run fine when cold and 20 mins later when warm make it run completely aweful? and three days in a row?

Thanks again for spending your time on me!

[Salty87]

89mariah....no sweat, it's more fun for everyone to get ON the water!

is it possible for bad gas to act up 30 mins later 3 days in a row....yes. you could be sloshing your tank around and kicking up debris/junk/water into the carb. this is the separator i'm talking about... http://www.boatersworld.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&catalogId=10051&langI d=-1&productId=361791
you might have an older filter that has a drain on the bottom. i had trouble finding a replacement filter for that one so i bought the new style. it was really easy to install.

with a new-to-you boat it helps if you get a firm starting point, new plug wires/plugs/new coil/full tune-up/etc. i have points though, never messed with electronic ignition, yet.

it could also be electrical for what you describe, the same as selle pretty much. check your cables also, if one is getting hot while you're trying to start the engine then you've got resistance building up. if you don't have a multimeter, i'd get one cause it will come in handy. it will tell you exactly how much charge your battery has and how much is getting to the solenoid, starter, etc.

there's a learning curve to getting an older boat running good, just like with a car. make sure you've got good belts/hoses/electrical/tuned up and timed right with fresh fluids. there's a thread around here for getting manuals too.

[Wino MO]

Have you done any work to the carb?
I have a 87 TS6M and the num-nuts I bought it from had changed the Factory Holley for a " off the AutoZone shelf " Edelbrock car model. The boat would start fine when cold but after running a while and warming up, if I shut the motor off the gas in the float bowls would boil over into the intake. Then when I tried starting it, the motor would flood and fail to start but the fuel pump would do it's job and re-fill the float bowls and the process would start all over.........

Try this, when you stop the boat, put the tranny in neutral and open the throttle to WAO and open the doghouse. when you're ready to restart the motor, close the doghouse and set the throttle to idle and turn the key. worked like a dream for me until I bought a new replacement Holley made for boats, not cars.......

Hope this helps,

MO

[89Mariah351]

Hey salty, that link says the seperator is for a mercury.. will that work with my PCM 351?


Thanks for the info MO. No, I haven't touched the carb yet.. it's the original Holley.
I'll probably end up rebuilding it or getting an already rebuilt one before the years over.

[selle92]

Salty,

thanks for the tips.- And sorry to hijack this thread...

I did check all possible sources and everything looked good. she seems to be running fine now. I'm thinking it was more "user" error being new to boating and after she was already warmed up, I should have just started it, rather than trying to warm it up more and ended up possibly flooding.- I don't know, but seems to be running great now.

J

[Salty87]

89mariah-

yup, that will work for your 351. you'll secure the base in a location where there's room to route the fuel lines...away from belts and stuff that might let loose at any point. neither the filter or the base will ever actually connect to your engine, just the fuel lines. i think i bought some extra fuel approved lines to install mine, the older hoses (gas or water) have no stretch left in them and get brittle. that can make it tough to cut an old hose and try to insert fittings. oil the seal a bit just like an oil filter.

selle-

a little flooded? haha, been there and didn't even get a t-shirt. my engine, when already warm, doesn't need any gas to start. when cold, 2 or 3 full pumps. if i miss getting it started (it starts and i let it stall), then i let it sit for a minute and open the throttle up as described a few posts above. just be ready to close your throttle when it fires up.


i should have parts waiting for me at home today, fingers are crossed! my boat's been dry since april.....ugh

[selle92]

Salty,

fingers crossed for ya. Gonna rain again this weekend here ( all of may was rain)... good thing I bought a boat this yr! blah!

[OUI]

Sounds to me like your electic choke isn't working or is adjusted wrong.