454 Mercruiser won't run under a load

[vamanos]

Any ideas or experience with a 454 running very well in neutral at any rpm, but not running under a load. It's a new rebuild and also rebuilt carb. Gas lines were cleaned with the carb overhaul. Thanks for your time.

 

[Black as]

Re: 454 Mercruiser won't run under a load

Any ideas or experience with a 454 running very well in neutral at any rpm, but not running under a load. It's a new rebuild and also rebuilt carb. Gas lines were cleaned with the carb overhaul. Thanks for your time.

You will need to check your timing, what sort of distributor do you have old style "points" or no points.

If you have points set them to specification and check the dwell angle and reset the timing.

 

[88beighlinercapri5.7]

Re: 454 Mercruiser won't run under a load

Yup, ignition timing. First, look up you timing settings. If you have points, get a dwell meter from parts store and follow the instructions. Next get a timing light and set the distributor advance. Lastly, zoom on the lake.

 

[vamanos]

Re: 454 Mercruiser won't run under a load

Does not have points. I drove this boat once with great performance. After sitting for two weeks the engine malfunctioned on the very next outing, today. Do your answers account for running in neutral at high rpm but not in gear?

 

[Black as]

Re: 454 Mercruiser won't run under a load

Does not have points. I drove this boat once with great performance. After sitting for two weeks the engine malfunctioned on the very next outing, today. Do your answers account for running in neutral at high rpm but not in gear?

Have you done anything to the motor in the past 2 weeks ?

 

[vamanos]

Re: 454 Mercruiser won't run under a load

Done absolutely nothing to the motor in the past two weeks. It has been sitting and on shore power trickle charging with the battery switch off.

 

[Black as]

Re: 454 Mercruiser won't run under a load

Done absolutely nothing to the motor in the past two weeks. It has been sitting and on shore power trickle charging with the battery switch off.

Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel
2. Propeller pitch or diameter, damaged blades
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
5. Marine growth on hull and outdrive
6. Wrong gear ratio in outdrive
7. Restricted carburetor air intake (clogged flame arrestor)
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
9. Poor cylinder compression Compression Test
10. Carburetor defective, or wrong type.
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed.
13. Engine Overheating
14. Engine timing and ignition system operation
15. Remote control cables and linkage for proper travel to open throttle plates fully.

 

[bruceb58]

Re: 454 Mercruiser won't run under a load

Don't do this.^^^^^

Set with a timing light to the spec. You also want to check the timing when the engine is at high RPM. The manual states what the distributor's max advance should be.

EDIT: Good...the guy changed his post from just manually turning the distributor and timing by feel.

 

[Black as]

Re: 454 Mercruiser won't run under a load

Don't do this.^^^^^

Set with a timing light to the spec. You also want to check the timing when the engine is at high RPM. The manual states what the distributor's max advance should be.

Why not, it works for me sometimes you do things old school way and work manuals were printed at the time of manufacture and years later we find a better way of doing it

 

[bruceb58]

Re: 454 Mercruiser won't run under a load

Why not, it works for me

Because its a sure fire way to have way to much advance and could end up burning a hole in your piston from engine detonation. You do it the correct way and use a timing light.

Am I of the understanding you never use a timing light?

 

[Black as]

Re: 454 Mercruiser won't run under a load

Because its a sure fire way to have way to much advance and could end up burning a hole in your piston from engine detonation. You do it the correct way and use a timing light.

Am I of the understanding you never use a timing light?

I definitely use a timing light, but one engine from the next aint all the same believe me, ask any mechanic that uses a dyno machine.

If you know what you are doing its as safe as ever

 

[bruceb58]

Re: 454 Mercruiser won't run under a load

Just tell that to the guy who tries this and grenades his motor.

Again to anyone reading this...don't set your timing that way.

 

[Black as]

Re: 454 Mercruiser won't run under a load

Just tell that to the guy who tries this and grenades his motor.

Again to anyone reading this...don't set your timing that way.

As I said if you know what your doing its fine, if you don't , don't do it ....easy !

And who's to say he may have spun is harmonic balancer

I could get that motor running "sweet as" with out using any workshop manuel, not saying he should do it but nothing beats a good ear and 50 years of motor experience

 

[JustJason]

Re: 454 Mercruiser won't run under a load

This might as well be a sticky on the main page because spring is a comming and people are starting to find out they have issues.

Here's the thread...
http://forums.iboats.com/showthread.php?t=295070


List of possible causes of low WOT (Wide Open Throttle) rpm.

In no particular order

Engine Won't Reach Operating RPM. Check

1. Fuel condition. Type and Octane possibly old fuel
2. Propeller pitch or diameter, damaged blades
3. Restricted fuel pickup tube or anti siphon valve Fuel System Test
4. Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
5. Marine growth on hull and outdrive
6. Wrong gear ratio in outdrive
7. Restricted carburetor air intake (clogged flame arrestor)
8. Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
9. Poor cylinder compression Compression Test
10. Carburetor defective, or wrong type.
11. Fuel pump pressure and vacuum
12. Boat overloaded, improperly loaded, or improperly trimmed.
13. Engine Overheating
14. Engine timing and ignition system operation
15. Remote control cables and linkage for proper travel to open throttle plates fully.

Thank Donny S when you see him for putting that info together. Your problem is in there someplace, just start and go down the list crossing things off as you go. You could also have a combination of problems to.

And oh yeah... I would never set timing on any engine that way either. Even if you got WOT timing right you'll throw off BASE timing, if you throw off base timing you'll never get the thing to idle low enough, and you'll end up trashing gearsets.

 

[vamanos]

Re: 454 Mercruiser won't run under a load

I take it the dizzy is the distributor? The Admiral seems to have my/the engine's best interest at heart so I'm going to go with him on this one. Can't hurt. Admiral, should I start with checking and setting the timing and is there anything else I should be aware of as the possible cause?

 

[Black as]

Re: 454 Mercruiser won't run under a load

I take it the dizzy is the distributor? The Admiral seems to have my/the engine's best interest at heart so I'm going to go with him on this one. Can't hurt. Admiral, should I start with checking and setting the timing and is there anything else I should be aware of as the possible cause?

Good luck, play it safe if your not sure start with the timing light and set it to the specifications in the book, but something doesn't sound right, your boat was fine last week and you've done nothing to it and this week it wont rev, have you looked at your fuel ?

 

[vamanos]

Re: 454 Mercruiser won't run under a load

Thanks Jason (Captain). I read through the WOT information at the sticky location. WOT is not really the problem. The engine breaks down under any load. The thing that gets me is the smoothness and powerfulness that it runs when in neutral.

This is a 1989 Searay and in great condition with a new rebuilt 454. Anyway, I realize that it this problem could be more than one thing and will try to sort it out, apparently with some help from you gentleman. Thanks much and I look forward to a new boat some day.

 

[vamanos]

Re: 454 Mercruiser won't run under a load

I will look at the feul this week. Thanks.

FYI: the boat stays in the water at a marina. And it has frozen a couple of times in the last two weeks.

 

[vamanos]

Re: 454 Mercruiser won't run under a load

Sorry to keep posting, but what I should have said is that the air temp has been about freezing and in the water should have been above 40 degrees. I am on Lake Travis in Texas so it can't get too cold.

 

[JustJason]

Re: 454 Mercruiser won't run under a load

WOT is not really the problem. The engine breaks down under any load. The thing that gets me is the smoothness and powerfulness that it runs when in neutral.

Whah??? Everything about that sentence is an oxymoron. Lack of proper Wide Open Throttle RPMS is exactly your problem. You realize that your engine will run on 3 cylinders when the thing is in nuetral and rev to 8 grand right? Reving an engine means nothing. Your engine is anything from powerfull if it's not hitting 4500RPMS under a full and heavy load.