525sc stalls when trying to engage gears
 

Can anyone help us, we have a 42' Formula with triple 525sc Mercruisers with Holley 1050 Dominators, we have rebuilt the carbs installed new power valves set float height, set fuel pressure, set engine timing to 10 degrees and checked the vacuum (pulling 11" mercury), any suggestions would be appreciated.

They ALL stall when put in gear? Did they do this before the work or after? Do they stall independently of each other or do they all stall when you put anyone in gear.

You should check your idle speed, it may be too low. My 525sc did not come with a fuel pressure regulator to "set fuel pressure". Your timing should be 13 initial (which would be 35 total @4500).

They all stall when individually put into gear, it would be OK if you had 4 hands, to shift from ahead to astern you need to select neutral with one hand kill the revs with the other hand and then select the opposite gear and at the same time try to catch it on the throttle while trying to steer!!

Thanks for this info will try it and fingers crossed it works because it is embarassing trying to negotiate a fuel dock or loch gate.

So they all just started stalling at the same time? Not one stalled at times then another and so on. Just one day you went for a ride and you couldn't keep any of the motors running when shifting? then you rebuilt the carbs and nothing changed still they all stall. I'm trying to figure if it is something in common with the engines, or the carb repairs. If rebuilding the carbs started this then its a pretty simple issue with the rebuild or setup. If they just started stalling all together before the carb work then we need to diagnosis a totally different problem.

Sounds like you have to forward the throttles to keep them going. still before or after the carb work.

Last what is the idle speed out of gear and in gear? Did you set the 4 corner idle mixture screws to best vacuum? Then re adjust the idle and do the mixture again until the mix is at best vacuum and the idle is to specs? What procedure did you use to set timing and at what RPM?

Generally speaking, when an engine dies going in to gear and the idle speed is set at the correct rpm, then the engine is usually to lean. Do as previously mentioned and set the 4 corner idle mixture screws to the highest vacuum setting. Ideally, you want to set the idle mixture and in gear mixture with a wideband O2 sensor. That is the best, most foolproof way to do it. If that is not an option, then use a vacuum gauge. Good luck.
Eddie

Don, the idle speed is 950rpm if you try to engage gear you have to blip the throttles or she stalls, ikt does this on all 3 engines, we set the mixture screws to one and a quarter turns out and then put a vacuum gauge and adjusted the mixture to give us best reading, we used a timing light to set the timing at idle but did not have any tape to check timing at 4500rpm so we do not know what the advance timing is.

The timing is correct?? Is it supposed to be 10 or 13 initial?

Understand you set the idle at max vacuum but I would still try adding a little fuel with the idle screws. Eddie is right the motors are probably too lean at idle if the timing is correct. BTW where did you measure the vacuum, above or below the blower?

Ok, I know some won't agree with this, If it were mine I would can the merc dist, run a mallory unilite or campairable stand alone dist, lock the timing curve and run about 28 deg, they will start fine with the low compression and the higher initial timing will clean the idle up and make the boat much easier to handle a docking speeds....this set up is what weiand recomends on their blower set-ups...Rob

They should idle at easily at 750-800rpms in neutral and not stall when put in gear. 950 rpms is way too high and you might even be getting a little advance from the module. If you have TB IV ignitions, the base timing should be set at 13*to get 35* total. The early 525sc used an older merc ignition with a slightly different curve. I don't know the specifics numbers on that one.

You need to get an adjustable timing light and set them on total timing. Initial timing is what it is. Every module is a little different in the amount of advance it has. They also will vary a little at which rpm they come in. So, ignore initial timing. Only use it as a reference to know you are close and set total advance.
Eddie

Thanks fro the help Don we ended up stripping the carbs right down and blowing out all the jets, re-setting the float height, vacuum and timing and it now behaves as it should, I think the boat has been standing a long while before we aquired it and the fuel had gone off more than we thought.

Thanks to all the guys who took the trouble to reply to try and help us out I think the main trouble was this boat has been standing for a while before we aquired it and the fuel quality was not good, we ended up stripping the carbs right down and blowing out all the jets, cleaning out the float chambers, resetting the float height, mixture screws and timing, this seems to have cured the problem as the boat now behaves in an acceptable manner for what we have.

Thanks again guys and I hope you all have a good Xmas.

Sounds good, I thought in your first post you said you rebuilt them. Had to do it again? Well glad it worked out.
Merry Christmas

FYI. IF the balancer is stock, it is probably marked for 35 deg timing-mine is. If you have mostly stock engines and ignitions, you will be better off running with all the advance (35 total) because it comes in late and will make your exhaust valves last longer. My boat had high leakdown through the exhaust when it was checked at less than 160 hours and I believe it was because the marina/previous owner thought they would "rethink" Merc Racings timing spec and run less timing.

My 525sc had a 35* timing mark filed into the balancer as well.

My only question is why merc is running 35 total, thats a ton on a blower motor..wieand who makes the set-up says keep to 26 total max ??

Merc set them up with low static compression which allows that much timing in boost. I run (525sc takeoffs) 28-30* with 9.5:1 static and it is safe but near the trouble area.

Merc set them up at 7.5 to 1 CR. They are very user friendly engines (that had a 90 day warranty) But not the ultimate blower motors, but very good conservative engines. I really like mine because it does not require a ton of maintenance and pushes my single engine, true 28 foot to "respectable" speeds.