[204Angler]

Have a new 4.3 engine installed in a ski boat. Replaced points/condenser with pertronix igniter. New coil. Two, fairly new marine dual purpose batteries. I've got a good solid consistent spark, compression and freshly cleaned and rebuilt Q-Jet with a new electronic fuel pump.

Engine specs call for 6* BTDC with 93 octane (which I run). It starts great with timing set at 12* but that is WAAAYYYY too advance when RPM's climb. Don't want to burn up this brand new engine. (remanned). In the back yard on the hose, it will run fine on 6* if I start it with timing advanced to 12*ish. When it is warmed up while running at 6* BTDC, I can cut it off and restart which it does just fine.

I have reset the base timing a dozen times. Same result. I have adjusted the idle speed but still no better. Today I went to the lake to try it and it won't stay running if I run the timing back to 6* from 12*. I have a feeling the back pressure from the water over the exhaust is the reason. Even still...I am confused on why this engine won't start/run with timing set properly. I know these symptoms usually point to either low compression or carb(s) in need of cleaning.

Any ideas? Thanks gents

 

[SnowCamp]

Along time ago, when I worked on engines for a living, we always disconnected and plugged the vacuum advance while working on timing
Any chance that's a necessary and neglected part of your process?

Sent from my C771 using Tapatalk 2

 

[204Angler]

It would be if I had a vacuum advance. It's mechanical

 

[204Angler]

If the springs for the weights on the dizzy were weak... Could that do it? I'm thinking the weights would have to stick to cause my problem but maybe I'm thinking about it backwards ??

 

[SnowCamp]

If the springs for the weights on the dizzy were weak... Could that do it? I'm thinking the weights would have to stick to cause my problem but maybe I'm thinking about it backwards ??

Weak springs would increase the angle of advance under acceleration.

 

[204Angler]

Right, so...even at idle, if it were weak springs or sticking weights (which I know they're not sticking) it wouldn't make a difference. They only advance timing with RPM's...like you said so, if I set my timing at idle, in gear in the water to 6* like the manual says to...weights wouldn't make a difference either way. Right? So, would could be causing this? Could it be my carburetor is still gunked up?? I have taken it apart three times and soaked it twice and used compressed air after both soaks.

I'm lost here. I TRY to do all I can before posting on here. I am about to bring this boat to a professional wrench before I jack it up so bad I make it harder on him

 

[sundrop]

You don't know the history on the boat. No telling what's been changed over time. The old school way is to set the timing where it cranks easy, advance it until the engine sound starts to "load up" like its binding up, then bring the timing back until it smooths out. If it starts smooth at that point when the engine is warm, lock it down and call it good. If it is hard to spin over back it down another little bit. That's how we did it w/o a timing light in the old days.

 

[sundrop]

Is it an actual marine engine or are you trying to use a truck motor? Very different cams and timing is why I ask.

 

[204Angler]

Is it an actual marine engine or are you trying to use a truck motor? Very different cams and timing is why I ask.

Yeah this is a marine engine. It is a remanufactured marine engine. I bought it brand new. I've got 7.3 hours on it...still trying to complete the break-in. I have set the timing the correct way, at least a dozen times. #1 TDC blah blah blah.

The boat is a 1987 however, I bought it from the original owner. He sold it to me because the engine was blown and I bought it to swap the interior over to another of the exact same boat I had. However, for $300 the rest of the boat and trailer was in WAY to good of shape for me to tear out the interior. So, I replaced the engine....the boat is just like it was factory. the guy didn't mess with it and had it professionally maintained. So, no crappy rewiring jobs or anything that is typical of old boats

 

[Fish_Fiend]

Remans can sometimes have short lifter or cam shaft flats. Especially if it was a factory reman...probably a long shot but ive seen it.

Gene - Red >X< - Asheboro

 

[204Angler]

You don't know the history on the boat. No telling what's been changed over time. The old school way is to set the timing where it cranks easy, advance it until the engine sound starts to "load up" like its binding up, then bring the timing back until it smooths out. If it starts smooth at that point when the engine is warm, lock it down and call it good. If it is hard to spin over back it down another little bit. That's how we did it w/o a timing light in the old days.

OH and I know it is advancing too far because it backfires when the revs get up closer to WOT. I am afraid that Ill get too much preignition one time and torch the engine

 

[204Angler]

Remans can sometimes have short lifter or cam shaft flats. Especially if it was a factory reman...probably a long shot but ive seen it.

Gene - Red >X< - Asheboro

I guess it's possible. I did get it from a pretty reputable shop in FL.

 

[sundrop]

a lot of reman shops use reground camshafts, generic timing gears/chains that cover many different year models requirements. It also might be a roller cam motor vs a flat tappet style. Sometimes the factory settings are just starting points. Also possible the timing chain/gears were installed a tooth off. Might have been built on a Monday morning or a Friday afternoon..

 

[Fish_Fiend]

Im not an engine guy. Insert Disclaimer here. But I did manage an Advance Auto for a time and ran into two remans in 3 years, which to me seemed like a high number, that had timing issues that were valve train issues in actual. I was just tossing it out there cause ive seen it.

Gene - Red >X< - Asheboro

 

[modenacart]

Sure you have TDC on the right stroke? Made that mistake with my car once.

 

[modenacart]

Of course you are able to start it so probably not.

 

[204Angler]

Yeah, she'll run decent. I used a compression tester to make sure it was on compression stroke but with a new engine, there is little guess work on which one is exhaust and which is compression.
In fact it I've run it to about WOT and hit 50mph. I was just afraid of preignition and popping a hole in a piston of a brand new engine. What I might do is just set the timing and idle speed to a happy medium, keep running premium ethanol free gas and just hope for the best.

I honestly don't know what it is and I got it to where it seems to idle the best at 11* BTDC which is fairly advanced but, I know what's important is 2500rpm which should be full advance. The mechanical advance is limited. There is a couple ways manufacturers limit HP and limiting spark advance is one of them. I haven't checked that yet.

The book says (for non-vortec) 27* btdc at WOT.... This engine should achieve 235 brake hp (probably 220ish at the prop) so perhaps a little further advance won't hurt as long as I keep good high octane gas in the tank. I might have to ad octane booster and that's a pain but I'd rather use the boat. Just thinking on "paper"

 

[sundrop]

Honestly if you have hit the limits of your abilities to diagnose this you need to turn it over to a pro. Small price to pay to NOT kill a new engine. Something isn't right. Not fixing it right will come back to bite you in time.

 

[204Angler]

Honestly if you have hit the limits of your abilities to diagnose this you need to turn it over to a pro. Small price to pay to NOT kill a new engine. Something isn't right. Not fixing it right will come back to bite you in time.

Exactly....that's what I'm gonna do