77 Merc 1150 Timing Problems

[mark_p]

Ok this one is kinda weird, i still havent figured out what is exactly going on.

About-
1977 Merc 1150
good compression 120psi +- on all 6
just cleaned the carbs
checked spark on all 6 - good
new wiring - everything matches wiring diagram
new fuel pump diaphrams on the way
etc....everything is in good working order

So i have been working to get my boat on the water for a while now...(its a 69 marlin that was in rough shape) and now i am to the point to get the motor running good, and have came across a timing issue that doesnt make sense to me. Any suggestions would be appreciated.

I have the service manual for the engine (if anyone needs it let me know because its on a cd and can email it) but anyways i read the timing section and have kinda stumped myself.

So the motor runs, but idles rough, on water the maxiumum rpm it will get up to is 4300 with a 13" by 19 pitch prop on a 16' boat. so not what it should be. so i got a timing light and set it to spec. 8 idle, 21 WOT...doesnt idle. tryed timing it by ear for the hell of it, and it was wayyyy advanced when i could get it to idle. so i pulled the distributor pulley cap and checked the timing marks and found something that doesnt make sense. SEE IMAGE BELOW

So the flywheel has a line on it that is about say 30 degrees couterclockwise of the 3 dots....the pulley on the distributor is lined up to the line. When i timing the engine with the light, i timed the 3 dots to where they should be... so it seems like everything should run right...but it doesnt...

so do i rip it apart and adjust it to were it should be? or is this set up like this for a reason that i am unaware of? And since it is set up the way it is...how did it work out that i have spark on the #1 at TDC, and it dont run well at all? I expect that most of you will say to set it back to the book (i plan on this). its just kind of running me in circles right now.

wow sorry that was kinda long. hopefully it made sense, ill be checking back in a few hours..so post away(please). thanks!

 

[jimg984]

Re: 77 Merc 1150 Timing Problems

i have a 1978 115 hp with a 17 pitch......... i think you are over prop. with that 19. 17 would bring thr rpms up these towers of power like doing high rpms. bet ur boat is a heavy fiberglass rite?

 

[mark_p]

Re: 77 Merc 1150 Timing Problems

yes it is fiberglass...i dont think that it is that heavy though, its not a tri-hull, and when i had the engine off to do some transom work it was quite lite. also the mercury manual says a 13 3/4" 19, 3 blade aluminum is right for 1500-2500 lbs, 16-19' boat, and the top speed should be around 35-42. i couldent get the boat over 30.

 

[wasp]

Re: 77 Merc 1150 Timing Problems

I have a 79 1150 and the idle is rougher than I like. I'm trying decarb and replacing fuel lines. I keep you posted on how that works. If I read right. You can't get it started at all. All the wrenchers tell me that if the motor is that out of shape. You should set it to factory settings. It is what I had to do.

 

[honestcharlie56]

Re: 77 Merc 1150 Timing Problems

i have an 84' 115, hard to start and def. rough idle. I would tell ya that nothing can replace the piece of mind that doing the job right is gonna give you. But at the same time if you adjusted the timing and it worked i would leave it, just make sure that you make adjustments according to the engines personality under load, just listening to the idle isnt the best way. good luck man

 

[Chris1956]

Re: 77 Merc 1150 Timing Problems

I am not sure I understood your post, but I have much experience with that motor. First make sure the outer flywheel is installed correctly. Turn #1 piston to TDC and make sure the timing pointer points to TDC or is at least very close.

Idle timing at primary pickup is 3-6 degrees BTDC. At actual idle speed, teh timing should be a bit retarded from that,

 

[mark_p]

Re: 77 Merc 1150 Timing Problems

thanks for the replys everyone, sorry my post is hard to understand, its kind of a weird situation.

maybe a brief restatement of the problem will help, so pretty much the timing arrow on the distributor cap does not line up with the #1 tdc mark on the flywheel, about 30 degrees advanced (like the picture) When i use a timing light on the #1 plug, i have to advance the distributor about 30 degrees before tdc on the cylinder to get a smooth idle. (which doesnt make sense at all). Anyways, i adjusted the timing belt by 3 notches to get the arrow to line up the other day, i want to time it before i start it.....ill keep you posted on what happens

a few answers to some comments,
yes, it does run, rough idle, and only when i advance the timing father then i should have to(for idle).

it almost seems like since the timing arrow was offset by 30 degrees, the tdc changed by 30 degrees. (i know that isnt possible)

ill update in a few days

thanks

mark