96' merc. 135 with intermittant stalling at low speed.

[tidechaser 1]

this motor had been sitting for years..i checked compression,replaced the water pump( note: tell tale seems to spurt and stop at idle and seems to be worse now after less than 8 hours run time). i run some junk through the motor to help remove oil build up..then took it on about a 45 minute run down a nearby lake. it ran good. i went into a 5 mile an hour zone and after going a good half mile suddenly it seemed like it was running out of gas..i hit the throttle and it bogged and died. after it set for awhile it started and ran ok..it make me nervous but it seemed fine for two more trips to the bay fishing..i did notice it would want to stall at idle though after a short time.
yesterday i took a few friends out on the bay..went out about 8 miles and anchored..it stalled a couple of times setting anchor. we took off a couple of hours later and ran in in windy rough water..came to 5 no wake zone and it seemed to be slowing down..same thing..crapped out again even though it had not done that for a couple of trips.
let it sit and used the kicker for awhile..then when we did get up on plane again the rpms were too high for the speed and it seems i may have spun the prop.hub as well?
just a couple of nicks on the new prop..no big bang felt etc.
sorry to be long winded..this is making me a bit crazy and nervous.
thanks guys.

 

[Bosunsmate]

Re: 96' merc. 135 with intermittant stalling at low speed.

Put a line of paint across the prop and shaft and see if they change when out and if so that will mean a spun prop.
Have you checked the thermostat and poressure relief spring, if they are playing up it could be overheating or overcooling

 

[tidechaser 1]

Re: 96' merc. 135 with intermittant stalling at low speed.

Put a line of paint across the prop and shaft and see if they change when out and if so that will mean a spun prop.
Have you checked the thermostat and poressure relief spring, if they are playing up it could be overheating or overcooling

thanks for the input..i did replace the thermostats already and i have installed two gauges..one for each cylinder bank..it seems to run cool at run speed..but under load at slow speed it seems to run warmer..but still pretty cool..never at the half mark.
guess i will bring my hand held and check the temp again when i get in in the water.
the weird thing is it started running lousy and i noticed the rt. gauge was a bit higher then the left. and both went up a bit..not hot though..just higher than they were before it started to bog out..seemed like it was running out of fuel. it would be much easier if it did this consistantly and i could get it to do it in a test tank.

 

[tidechaser 1]

Re: 96' merc. 135 with intermittant stalling at low speed.

btw..cant remember where the pressure relief spring is..? how would that affect it?
thanks.

 

[Bosunsmate]

Re: 96' merc. 135 with intermittant stalling at low speed.

It may of being running a bit lean so that would of increased the temp. Have you looked at the inlet reeds?

 

[Bosunsmate]

Re: 96' merc. 135 with intermittant stalling at low speed.

btw..cant remember where the pressure relief spring is..? how would that affect it?
thanks.

If it was broken it would not put enough pressure on the thermostat housing and so more water would enter at idle overcooling it but since your temp goes up it doesnt seem the issue

 

[tidechaser 1]

Re: 96' merc. 135 with intermittant stalling at low speed.

i have not taken carbs off yet..i need to check the actual temps at the heads..they were fine the last time a checked..i think about 160 with the muffs on. it has run pretty well..it was just slowly dying at idle..mainly when cold. i am going make a tank and test it in the tank..maybe under load it will have the problem and i can check temp at both cylinders then.
since it was cruising fine at slow speeds most of the time and has not been consistant i am not sure where to start..could be electrical or fuel related i guess.

 

[Bosunsmate]

Re: 96' merc. 135 with intermittant stalling at low speed.

If you have a timing light next time it bogs down, hook it up to each spark wire and see if they are sparking, dont worry about timing just check it flashes. A hot coil can cease to function if starting to fail

 

[tidechaser 1]

Re: 96' merc. 135 with intermittant stalling at low speed.

If you have a timing light next time it bogs down, hook it up to each spark wire and see if they are sparking, dont worry about timing just check it flashes. A hot coil can cease to function if starting to fail

thanks..i remember that coils can do that..yes..but by the time i got it hooked up the motor would be dead and would not start and run for awhile..that is the type of thing that i am wondering about,but one coil out of six would just cause it to run lousy i would think..not bog and die wouldn't it?

 

[Bosunsmate]

Re: 96' merc. 135 with intermittant stalling at low speed.

Yep but maybe its more than one or it will show its something else in the ignition that causing a no firing condition on a few cylinders such as on one bank. If you do it while dead and its not starting then it will clearly show whether its not sparking then

 

[tidechaser 1]

Re: 96' merc. 135 with intermittant stalling at low speed.

update:
i took my temp gauge and ran some checks. i ran in in a barrel i cut a slot in and layed sideways so i was not using the muffs.
it seemed to idle too low..about 800 maybe. it was spurting out water until i hit over 1000 rpm and didnt seem to be continuously streaming until a bit higher. i ran it quite awhile and just off of idle and the top of the cylinder heads finally heated up to about 110 0n the left bank and about 120 degrees hotter on the rt...maybe the way it gets water when there is not much flow? the gauges on the dash both show the same differences at lower rpm..when it gets up higher rpm,like when planing,they seem pretty even temperature.
when i ran it up to about 2000 and held it there for awhile i noticed it started to go down maybe 400 rpm's after awhile and then in a minute or so it came back up and was a little higher rpm. under load it might have been worse and died..not sure.
i had a similar issue on my 75 hp. merc. tracker motor and i think after cleaning out the carbs and adjusting them again that issue seemed to be mostly gone.
there is an adjustment on the throttle linkage that i likely screwed up when i was trying to get the idle up..this was before my last trip out..i am not clear on the adjustment..the book is not helping me on that. that may have aggravated the issue..but it did die in the same manner before.

the temperature does measure about 20 degrees or more cooler when at higher throttle..it makes me think i put the thermostats in backwards..lol....but i think they were 140 degree thermostats..and my guess is when they open at 140 the engine gets that much cooler.
i noticed when i got the motor up high in rpm's and it got measured only about 85-90 degrees at the top of the cylinder heads. i brought the engine to a low idle then and it got pretty hot..when touching the top of the heads it felt very hot..but not hot enough to burn me. hope something in all this b.s. seems to make sense? lol.
i am suspicous of the big temp swing..and of the carb idle circuits maybe having some junk in them maybe?

 

[tidechaser 1]

Re: 96' merc. 135 with intermittant stalling at low speed.

Yep but maybe its more than one or it will show its something else in the ignition that causing a no firing condition on a few cylinders such as on one bank. If you do it while dead and its not starting then it will clearly show whether its not sparking then

good point. i cant get it to die while running in the barrel..but i will buy another timing light and bring it along next time..cant hurt to help narrow it down no matter what.

 

[Bosunsmate]

Re: 96' merc. 135 with intermittant stalling at low speed.

Is your timing alright at idle?
You could be right about carb idle circuits, normally you will get a backfire on them though if they are blocked and you are on muffs but its probably worth a clean either way.
When you pump the bulb tilt the engine up a bit and see if any fuel leaks a carb thus out showing a flooding carb from failing float etc

 

[tidechaser 1]

Re: 96' merc. 135 with intermittant stalling at low speed.

Is your timing alright at idle?
You could be right about carb idle circuits, normally you will get a backfire on them though if they are blocked and you are on muffs but its probably worth a clean either way.
When you pump the bulb tilt the engine up a bit and see if any fuel leaks a carb thus out showing a flooding carb from failing float etc

interesting..i have not tried lifting the motor up a bit and checking for flooding..thanks for the tip!
the motor does not run smooth until it is warmed up..i think i am going to pull the carbs off and clean them out..a bit of work but i think it should be done for piece of mind if nothing else..tomorrow after work i will start on that.

thanks for the help bosunsmate!

 

[tidechaser 1]

Re: 96' merc. 135 with intermittant stalling at low speed.

update:
after taking the carbs apart and checking-cleaning them i didnt see any debri,water,corrosion. everthing looked good. i removed the jets and inspected them. all i found was a tiny bit of something in one idle jet.
the engine runs the same still now.
i took off the lower unit and inspected the water pump impeller etc. it seemed to have only a tiny set in it and looked nearly perfect.
the only thing else i did was put re-do the sealant at the back of the area where the exhaust is..i had not done that the last time. also i pulled up the base and replaced the seal and o ring.
when running in the bucket it still barely spits occasionally..idling at around 700. it is a pressure pump and not a volume pump by the way. i notice even using 1500 rpms the stream is not continuous..it has to be over 2000 to be continuous..this does not seem right so i guess i will order another kit and look for other reasons for it to be not pumping well at idle.
today i am going to try to readjust the idle mixtures and make sure the throttle plates are all closed etc.

 

[tidechaser 1]

Re: 96' merc. 135 with intermittant stalling at low speed.

adjusted the throttle plates to make sure they were closed,checked for water in the fuel and adjusted the idle jets. runs a bit better but when holding rpms at upper mid rpms it still will start crapping out and then the rpms get higher..it almost seems like an air leak..except it seems to run pretty well at idle and just off of idle and it did seem to run fine on the water at cruising speed..but again after it slowed down off of plane is when it crapped out and would not even start for a while.
i will have to try it on the water now that the water pump seems better etc...but i am missing something i am sure.