timing a 1990 454 the correct way help

bolo78910

Chief Petty Officer
Joined
Jun 25, 2006
Messages
503
hello iboats well am back again .i want to know the correct way for timing my 454 mercruiser. .what i did was at idle speed 700 rpm i just set the timing at 8 btdc and lock the distributor down, the problem am having is, with load it will not go past 3800 rpm . even when i drop down to a pop two pitch lower same thing. i was told maybe i need to do the distributor advance time correctly so it can reach the correct rpm. compression is geat on all cylinders . 25 sea ray i got 30 mile per gps at 3800 rpm with only a 15 x15 mriage prop i know the correct prop should be a 17.. thanks guys am about to get me a advance timing light. thanks for some info. god bless
 
Joined
Mar 27, 2010
Messages
3,008
What kind of ignition system do you have? Points or electronic?

Here is the link to your factory service manual.... It will open to the 3-possible distributors... Mallory, Prestolite or Thunderbolt IV (HEI) which do you have?

http://boatinfo.no/lib/mercruiser/ma...er15.html#/302

Timing procedure is in that link also just depends on which one you have..... follow the Table of Contents to the ignition timing for the correct distributor...
 
Last edited:

bolo78910

Chief Petty Officer
Joined
Jun 25, 2006
Messages
503
thanks very much, i have the thunderbolt iv i think the distributor ha # like J11 thanks much.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,582
Timing is set at 8 BTDC as you listed. Timing advance should be 14 degrees for a total advance of 22 degrees.
TB4 Advance curve.jpg

If you are getting 14 additional degrees timing, the next thing I would check is the engines compression
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Couple of things to check. Make sure you have the right module (look for ALL the numbers on it)... Do a compression check, and check, double check, triple check the spark plugs leads are on the right plugs (firing order).

2 questions. 1-Has the engine been running right? 2-What work has been done on the engine between it working right and now having the problem?

Chris..........
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,468
the problem am having is, with load it will not go past 3800 rpm . even when i drop down to a pop two pitch lower same thing

Ayuh,..... Check the Contents of the fuel filter for water, 'n crud,.....
 

bolo78910

Chief Petty Officer
Joined
Jun 25, 2006
Messages
503
thanks eveyone, well today i went back to mess around the engine, first with the engine on tdc timing set at 8 degree dizzy bolted down . the rotor was pointing straight center off the thermostat housing # 1 spark plug wire on top. after taking off the cap i notice the little pin in the middle off the cap was gone. i install a new cap and rotor. now i ask my buddy to rev the engine up to 3000 rpm and hold it there while i keep the timing light steady on the 8 degree mark at idle. it advance about one inch and halh to two, roughly two, so my gess is that it is advancing but without a advance timing light am just gessing. bondo i put a new water separator filter early season . i will pull it and the carb filter and see whats up. achris its been running great from i launch it in april fishing was close to home so i did not try to go open throttle antil a few week ago. alldodge i will do a complete compression test this weekend. plus go back over the wiring , and about the module make a lot off sense. after i change the cap and rotor today i took her for a run and this is the result at 3800 wot fully trim 27 miler per gps. wont rev no more... in nutral it rev over 4000 rpm briefly. thanks guys will post my finds
 

bolo78910

Chief Petty Officer
Joined
Jun 25, 2006
Messages
503
hello again I thought I just put this in. A few weeks ago my alternator belt was squeaking it was a little loose so I tight it down some. The next day I took the boat out and hit the throttle to gets her on plane. The boat did not wants to go . it was revving but was not biting. I open the hatch and smell burnt rubber. I thought it was the belt that I make more tight was burning. Could it be my coupler . omg I hope not. I will go back there tomoro put some white out on the coupler to mark it and take it for a spin. Ur thought.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,582
hello again I thought I just put this in. A few weeks ago my alternator belt was squeaking it was a little loose so I tight it down some. The next day I took the boat out and hit the throttle to gets her on plane. The boat did not wants to go . it was revving but was not biting. I open the hatch and smell burnt rubber. I thought it was the belt that I make more tight was burning. Could it be my coupler . omg I hope not. I will go back there tomoro put some white out on the coupler to mark it and take it for a spin. Ur thought.

Yep sounds like the coupler. Has it been a while since the last time the alignment was checked?
 

bolo78910

Chief Petty Officer
Joined
Jun 25, 2006
Messages
503
Last season the coupler did give me a warm time to alighn. But I did get it as close as I could. it seem the coupler was warp but when the yard mechanic was installing the drive he told me I did a great job on the alignment. . Hope it last me for the season @ 3300 rpm it is doing 20 knots. With no slipping. Will mark the coupler wensday install a new prop hub and take it for a hard run..
 

bolo78910

Chief Petty Officer
Joined
Jun 25, 2006
Messages
503
up date , went back today to try figure things out.

firing order is good

fogot to check the fuel filters ugg

put a mark on the coupler using white out, took it for a run same thing ,but on my way home i think i did not mark the coupler in the correct place.

i thing i deed to put a mark on the drive shaft too. so that was a waste off test.

this is the numbers on the module on the risers. thunderbolt 1V # 0623A V8-24 is this the corect one thanks.
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,582
Unable to find the number listed, the part number should be 15248A1 (old) or 15248T02 (new), the V8-24 does indicate it is for a V8 and has 24 degree advance, which is what your engine requires
 

bolo78910

Chief Petty Officer
Joined
Jun 25, 2006
Messages
503
Serial number is. 0D389808. So you guys think I might have the wrong module. See if this module number is correct. 0C23A V8 -24. The one I post before might be a c. Instead of a 6 It fade slightly. Thanks
 
Last edited:

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,582
Serial number is. 0D389808. So you guys think I might have the wrong module. See if this module number is correct. 0C23A V8 -24. The one I post before might be a c. Instead of a 6 It fade slightly. Thanks

I'm not saying you have the wrong unit, only mention that the numbers you are providing to not match to the Merc part numbers. That said you do have a V8 module with 24 degrees of timing, which is what your engine should have. Just check your timing curve to match up with the one Chris posted. Should have 15 to 18 @ 2400 rpm and 22 to 25 @3700 rpm. If the curve matches you have the right one

Remember to add 8 BTDC to all readings
 
Last edited:

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Serial number is. 0D389808. So you guys think I might have the wrong module. See if this module number is correct. 0C23A V8 -24. The one I post before might be a c. Instead of a 6 It fade slightly. Thanks

If you have a Bravo 1 or 2, then you have the correct module.
 

picklenjim

Chief Petty Officer
Joined
Mar 11, 2009
Messages
528
I'm not saying you have the wrong unit, only mention that the numbers you are providing to not match to the Merc part numbers. That said you do have a V8 module with 24 degrees of timing, which is what your engine should have. Just check your timing curve to match up with the one Chris posted. Should have 15 to 18 @ 2400 rpm and 22 to 25 @3700 rpm. If the curve matches you have the right one

Remember to add 8 BTDC to all readings
If you have a module giving you 24* of advance and you add the 8* initial you should have a total of 32*. I can assure you a 454 needs 32 to 34 degrees of total timing. You need to get a timing tape to put on your balancer so you can rev the engine and set your timing while it's at full advance. Then just let it be where ever it ends up being at idle. I think you will find it will run better at 34 total and at 10 idle you will have a cleaner stronger idle.
http://www.autozone.com/ignition/timing-tape/mr-gasket-timing-tape-performance/193945_386909_0/
 

bolo78910

Chief Petty Officer
Joined
Jun 25, 2006
Messages
503
up date here guys. this is what i gotten done today.

change fuel filter to carb which was very dirty.

mark off the couple with some whitout to see if it will slip.

change the hub on the prop.

timing was off it was set at 10 so i put it back to 8 at 700 rpm.

took it for a run lot off boat traffics so i did not get to do much .this i get it up to 4000 rpm .....but i just knows something is not right.

return back to the dock . pull plug wires one by one and found # one cylinder not firing.

i swap the wire from # 2 over to # 1 this time #1 is firing and # 2 stop firing , at closer look at the wire it has small cuts close to where it goes over the spark plug, about three cuts that exposed the metal in the wire. god am praying this is the problem , will get a new set off wires. will post the outcome.

thanks
 
Last edited:

bolo78910

Chief Petty Officer
Joined
Jun 25, 2006
Messages
503
by the way the coupler did not slip by looking at the mark i put on the shaft/coupler
 
Top