1974 165 hp mercruiser misfires on sudden acceleration

[chris812]

Hello all, I have a mercruiser 165 hp 1974 and have been working on the engine for a while now. I took the head off to replace the gasket, replaced the head and adjusted the valves (to the best of my knowledge) according to the manual. So had it out in the water to test it out and it idled good. once I accelerated it would cut out and backfire. seems like the valves are knocking a bit too but I checked them and they seem snug. I did have to take out the distributor and fix the advance weight because they were rusted. Prior to that I had no advance on the timing. After I ran the engine after fixing the distributor, I put the timing light on and noticed the timing mark way behind the timing like 30 to 40 deg instead of 8.
I am assuming that i may be one sprocket off. could this explain the problem with the backfire and poor acceleration? It was doing the same thing with the backfire and poor acceleration before I fixed the distributor.
If someone has any ideas please let me know.

HAPPY NEW YEAR!!!!

 

[Fleetwin]

Re: 1974 165 hp mercruiser misfires on sudden acceleration

Hello all, I have a mercruiser 165 hp 1974 and have been working on the engine for a while now. I took the head off to replace the gasket, replaced the head and adjusted the valves (to the best of my knowledge) according to the manual. So had it out in the water to test it out and it idled good. once I accelerated it would cut out and backfire. seems like the valves are knocking a bit too but I checked them and they seem snug. I did have to take out the distributor and fix the advance weight because they were rusted. Prior to that I had no advance on the timing. After I ran the engine after fixing the distributor, I put the timing light on and noticed the timing mark way behind the timing like 30 to 40 deg instead of 8.
I am assuming that i may be one sprocket off. could this explain the problem with the backfire and poor acceleration? It was doing the same thing with the backfire and poor acceleration before I fixed the distributor.
If someone has any ideas please let me know.

HAPPY NEW YEAR!!!!

I think you answered your own question. Timing is WAY off. I suspect you are a tooth or more off.

 

[chris812]

Re: 1974 165 hp mercruiser misfires on sudden acceleration

how do I make sure I got the tooth in the right spot or how can I relocate it to make it right?

 

[thumpar]

Re: 1974 165 hp mercruiser misfires on sudden acceleration

Put cylinder #1 at the compression stroke of TDC. Pull the distributor and put it in with the rotor pointing at the #1 plug wire position.

You may be able to rotate the distributor to fix it but I would do it right.

 

[chris812]

Re: 1974 165 hp mercruiser misfires on sudden acceleration

thanks thumpar, I will try that.

 

[Bondo]

Re: 1974 165 hp mercruiser misfires on sudden acceleration

thanks thumpar, I will try that.

Ayuh,... If that don't fix yer backfirin', 'n poppin',....

Check, 'n change the fuel filters,....

A Lean condition is the next thing on the list of yer symptoms,....

 

[alldodge]

Re: 1974 165 hp mercruiser misfires on sudden acceleration

Hello all, I have a mercruiser 165 hp 1974 and have been working on the engine for a while now. I took the head off to replace the gasket, replaced the head and adjusted the valves (to the best of my knowledge) according to the manual. So had it out in the water to test it out and it idled good. once I accelerated it would cut out and backfire. seems like the valves are knocking a bit too but I checked them and they seem snug. I did have to take out the distributor and fix the advance weight because they were rusted. Prior to that I had no advance on the timing. After I ran the engine after fixing the distributor, I put the timing light on and noticed the timing mark way behind the timing like 30 to 40 deg instead of 8.
I am assuming that i may be one sprocket off. could this explain the problem with the backfire and poor acceleration? It was doing the same thing with the backfire and poor acceleration before I fixed the distributor.
If someone has any ideas please let me know.

HAPPY NEW YEAR!!!!

The hydraulic lifer adjustment needs to be accomplished with a warm running engine. Manual says to back off each rocker stud one at a time until they start to clatter. Then tighten rocker stud until it stops, this is zero backlash. Continue to tighten the rocker stud 1/4 turn, wait 10 seconds for engine to smooth out, repeat until you have 3/4 turn. Repeat this step with each rocker stud.

 

[998cc]

Re: 1974 165 hp mercruiser misfires on sudden acceleration

I would also double check the point gap while you have the distributor out. Then after restarting and setting timing, adjust valves as in the post by Alldodge above; just snugging them up all but guarantees improper adjustment.

 

[Berto95]

i have the same motor but when I accelerate it only goes up to a certain speed and no more is it the carb or gas filter ? I been working on I for a while took it out and it gets from point a to b but at only 15 mph

 

[jbcurt00]

Berto, no that you've got a topic of your own about your Mercruiser, best to leave inactive topics, inactive. After 90days, treat inactive topics as library books, for research only, and not to be written in.

Thanks, welcome to iboats.

Lets let this topic go back to the archives w no more new posts.