540 will not idle
 

We put a pair of rebuilt 540s(crank polished and magnafluxed, new rings, bearings, block boiled, new lifters) in the boat using the same electronics, 1050 dominator, etc and now the port motor won't idle. We've replaced all the ignition components, the carb, checked the fuel pressure, checked for vacuum leaks and now, I personally, am out of options...the guys at the shop are still scratching there heads and I'm sure they'll figure it out, but does anyone have any ideas?

Sean, need to be more specific on wont idle. does it stall or just wont idle down? if stalling at what rpm, or when putting into gear? i assume the other engine is ok, what ignition system are you running?

The ignition is the old style Mercruiser...it's Thunderbolt something...sorry I can't be more specific, but the boat is a 1987 and the original motors were 420s. The other motor runs fine(in fact, we took most of the accessories off of it to try and troubleshoot this problem) and the idle problem is in nuetral. We haven't even attempted to try and put it in gear.

The motor will not stay running at 1500rpm or below. It will stall unless you give her some gas. The fuel pump has been replaced as well and she appears to be getting plenty of fuel.

Spray the carb area with starting fluid and if the RPM's change you have a vacuum leak. Check you motor with it running with a vacuum gauge. My guess is that this will lead you to your problem. Possibly the intake is not matching the heads and you may have a vacuum leak from the underside, check you oil for water, if vacuum leaks probably the water ports will too.

Sean, sorry to hear your having troubles with the new engines. Are your 540's tall decks? If so, what intake manifolds are you running. Just curious.

Good luck fixing the problem.

Check that you have enough initial ignition advance. My motors won't idle well below 14 degrees initial, and really are happier at current 18 degrees. I shortened the advance to keep 35 total. Bigger cams and bigger bore both want more initial advance (bigger bore but same flame front speed needs more advance).

Check that you don't have a bad power valve. Have had blown ones dump so much fuel that they won't idle, but will run once you open it up a little so it can absorb the extra fuel. Might try swapping carbs with the one that runs and see if the problem moves with the carb.

-Greg

Thanks for the suggestions. We swapped carbs from the good motor with the same result. The starting fluid idea sounds like a good idea.

The motors are tall decks and I'm running Team G manifolds...not tall deck manifolds, so there's a spacer in there to make up the difference. We took the entire intake assembly apart, cleaned and resealed...still won't idle...:(

The timing idea also sounds valid...I noticed the timing was "all over the place" but I'm not sure how advanced it was. Is it possible that the timing chain is off by one tooth or possibly 180 degrees?

Sounds like a vacum leak...intake spacers can be a pain. When you say the timing is all over the place...is that on the light?
One other thing that can cause a rough/poor idle is having a valve out of adjustment (too tight)
Dan

Dan,

Yes, on the light, the timing seems to be all over the place. I never thought about the valves though either.

Thanks for the suggestions guys, I'll let you know what the outcome is.

Sean

Maybe the cam a tooth off?

Jon

Okay...when they reassembled the motor, they could not get the Crane 99377 hydraulic lifters, so a set of "race" lifters were ordered from the local auto parts store....

The initial thought was just what you said, Jon, but the timing chain cover, pulley and balancer were removed and the timing marks were right on.

Sooo...were looking to get the correct Crane lifters and try that on for size...any thoughts?

Sean,
Stupid question,did they have the race lifters in both engines? I hope you get it figured out soon. I want to see that boat in the water!

Gary,

Cranes in both motors and when they rebuilt the port 540, they couldn't get Cranes in time, so they opted for the "race" lifters from the auto parts store...I have a feeling these lifters are junk.

Sean

Sean,
World products (Merlin) makes a Marine manifold for the tall decks. They make them for 4150 carbs or 4500 depending on what you have. I bought a couple and got rid of the stinking spacers. When I took them off, I noticed leaks all over the place. Could have led to my detonation. These manifolds have brass clad water jackets. (very cool). Good luck with the lifters.

Sean, your best, single means to chase this problem is the vacuum gauge. Have you stuck one on and read it? It will tell the tale. tight valves won't produce enough vacuum to pull fuel and atomize it. Try taking a turn out of them and and starting it. Last year,an ignition module did the same thing to me. The mark was all over the place. As for the timing being retarded, loosen the distrib and knock it a few counter clockwise. My 600 inch motor this weekend took 14 degrees initial before it started to idle better. Probably not your carb if you swapped them over. Dan

Sean
Crane hyd roller lifters require a different pushrod. If you used crane pushrods with X brand lifters Me thinks you may have created the problem. Seems to me the crane PR are about 1/8 or so longer...intake and ext.
DanL is right...put a vacum gauge on that puppy

Dan

Thanks DanL and DanB...I'm learning alot here! I appreciate all of the advice. There are many things here I just did not know.

DanL, we looked at the Team G manifild and there didn't appear to be any spot to install a vacuum guage other than drilling the manifold below the carb...should I be looking elsewhere? I ordered the Crane lifters and had them overnighted...hopefully they'll arrive tomorrow.

My quesiton is: Could those inferior lifters have damaged the pushrods? Will I have to replace them now too?

Here's another question: The guys at the shop tell me they don't look at the initial timing...only at about 3000 or so, they aim to get somewhere between 32 and 36 degrees. Does this make sense?

Jim, I am thinking about your suggestion...maybe this winter I will change them over...or just sell 'em an buy some NEW Mercury WARRANTEED motors :|

Your help is greatly appreciated

there should be a nipple on the carb, front metering block, right side, or stbd side, on a 45 degree angle with a rubber cap on it. Thats for the vac gauge. As for the pushrods, roll them on a flat surface and look at the ends. They're probably ok. The initial advance needs to be set and then the modules changed out to get the desired total. On the race boat, we lock out the advance and set the engines for 36 right at idle. Good luck.

Thanks Dan. I'll check the rods...Idunno if the 1050s have that nipple on 'em but I'll also check on that. Thanks again and good luck with your vibration problem...wish I could help you...but like i said, I'm still learning.:( :)

Maybe this is a stupid suggestion, but I am just trying to think of something that has not been said. Is there any chance those " RACE " lifters are solid lifters and not hydraulic????

Thanks everyone...the Crane lifters arrived today, were installed and solved the problem. DanB wins the prize...! Thanks again! Testing propellers tomorrow! Tryin to spin a 28 or 30 Bravo...

Hey Sean,

Let me know how the boat runs with the new motors. I'm curious to see how much speed you get out of these puppies! What kind of power are you getting from them?

Mongo

That's good news Sean! I hope the testing goes well! I could be wrong, but I think a 26 B1 at about 5400 rpms:D

I'll say 24P Bravo1.:D

Sean, I have been following this post and I`m glad the problem is fixed. There is a TON of knowledge here and I seem to learn something new every day.

Good luck and happy boating, Kurt.

No problemo Sean
Glad I could be of help....good luck with your props
Dan

UPDATE
 

I should have posted earlier, but I thought I'd let you guys know that we got the lifeters in and ran the boat for about 10 min on th hose and 20min in that bay. Varying RPMs from idle up to about 4800 with a pair of 26 Bravos...I could swear I should be getting mor r's out fo those props, but that's another story.

The real story is the lifters and my MSD ignition!:mad: :mad:

One of the brand new Crane 99377 lifters collapsed after 30 minutes of running(Ithought a bearing let go again)...man this is pissing me off. So, I call Summit, who tell me to call Crane, who send me a pair 2nd day air. The mechaic is putting them in now...so we'll see.

My brand new MSD 6AL came back from Autotronics and still does not work...I called them and now I have to send that back too...

This stuff is really beginning to piss me off...

Hang in there Sean. You'll get it together. We will be heading out east tomarrow till Labor Day:D Hope to see you at Claudios.

Ken, I'll be there!

BTW, my mechanic doesn't want to re-use the other lifters...says we should replace the entire set, but guess what...world wide backorder! :mad: :mad: :mad:

I'm starting to wonder who I've pissed off...

:D