Help with Mercruiser 470 inboard

[USA Shooter]

Does anyone know what the timing should be set at on a Mercruiser 470 4cly? Thanks for the Help

 

[ne7800]

Re: HELP with Mercruiser 470

Re: HELP with Mercruiser 470

I belive it is 8 degrese BTDC @ 700 RPM

 

[bhammer]

Re: HELP with Mercruiser 470

Re: HELP with Mercruiser 470

USA, It is actually 4 BTDC. There was a service letter issued that changed it becasue of the newer fuels. Here's the letter.

Initial Timing Specification
Change For All 3.7 Litre
(224 CID) Engines
The quality of todays fuels have changed considerably
over the last 5-10 years. Because of this, the 3.7
Litre and 3.7 LX Litre MerCruiser engine timing will be
set (by the factory) at 4 degree BTDC. The timing
specification will be unnoticeable in performance for
all practical purposes and allowing for more tolerance
to todays fuels.
It is suggested that when a dealer services one of the
following engines, the ignition timing be reset to 4 degree
BTDC instead of the original 8 degree BTDC. All
service manuals will be changed in the future to reflect
this timing change.
MIE 470
MCM 470
MCM 485
MCM 488
MCM 165
MCM 170
MCM 180
MCM 190
MCM 3.7 Litre
MCM 3.7 LX Litre

Taken from a Merc.TSB 87-17

 

[ne7800]

Re: HELP with Mercruiser 470

Re: HELP with Mercruiser 470

lol i stand corrected

 

[Don S]

Re: HELP with Mercruiser 470

Re: HELP with Mercruiser 470

It also depends on which year and which distributor you have in it. You could have either the Delco, or the Prestolite. Makes a difference.

 

[USA Shooter]

Help with Mercruiser 470 inboard

I have a 1982 Mercruiser inboard 470. I have spark and I have checked the timing and it looks to be all lined up but I can not get the motor to start, It just cranks over and the carborator is blowing fuel out the top instead of sucking the fuel down ? All the help will be appreciated. Thanks for reading

 

[USA Shooter]

Re: HELP with Mercruiser 470

Re: HELP with Mercruiser 470

Thanks for the help. I am still working on it and trying to get it to run. I think it is still out of time due to it blowing gas out the carborator instead of sucking it in. It will turn over and over but wont run and I have good spark

 

[Don S]

Re: Help with Mercruiser 470 inboard

Then you DO NOT have the timing right. Probably 180 out on the distributor.
Did you have the distibutor out or the wires off the cap? Do you know how to find #1 TDC on the compression stroke?

 

[USA Shooter]

Re: Help with Mercruiser 470 inboard

Well I thought I did but the way the boat still wont run I guess I dont.

 

[langford7]

Re: Help with Mercruiser 470 inboard

Well let's see if you are. You will have to take off your valve cover to help aid in timing it. First take out number 1 plug (the first one when you are facing the stern). Now put a long screwdriver in the plug hole and use a socket on a breaker bar to turn the crank till the screwdriver is at the top. Make sure it is at the top and not on its way down. Now look at your valves, they both (intake and exhaust) should be closed. Now take the distributor cap off, the rotor should be facing the number 1 plug. If not you are a 180 off. Take the distributor off and turn it 180. If it does not want to drop in facing number 1 have a friend turn the crank just a little till it drops in.

The cylinder and firing order are stapmed on the intake manifold.

Hope this helps....

 

[Don S]

Re: Help with Mercruiser 470 inboard

There is an easier way to find TDC of #! without pulling the valve cover or sticking screwdrivers in the spark plug holes.
Just pull the plugs (all of them) then put your compression tester hose into #1 cylinder (front of engine) rotate engine in the normal direction of rotation with your thumb over the end of the hose, when you start feeling pressure build, continue turning in the direction of engine rotation till the timing marks align. Bingo, #1 TDC on the compression stroke.
Now look at your rotor, it will be pointing to where #1 spark plug wire should be located, firing order is 1-3-4-2 and the rotor turns clockwise.

 

[USA Shooter]

Re: Help with Mercruiser 470 inboard

Thanks for the help. I think I am in over my head and will have to get someone to help me