Starter Anxiety 7.4 MPI

sprink56

sprink56

New Member
Oct 28, 2008
1,288
West Palm Beach, Fl
Boat Info
1979 255 Liberator
Engines
twin Mercruiser 450 HP I/O on Bravo I Drives
We had a great day on the water yesterday, made a trip of about 40 miles total, non-stop.

Got back to the marina and cleaned the boat. Just before we left I decided to start the engines to check them out.

The port engine started but the starboard engine would not turn over...nothing. I tried several things including emergency start...no go.

I went back to the marina today armed with tools, volt meter and manual. I vented the bilge and tried the starboard engine...started right up:huh:no problem.

Whats going on?

Engines are 7.4 Marine Power MPI...new 625 hrs ago. Batteries are new as are the cables.

What concerns me is when will this happen again?
 
Happened to me that same way once - one of the grounds was loose - tightened the cable and no problem since....
 
Might be a lot of different things. Could be wiring, you need to check the cables and connections. Could be a temperature sensitive part like a relay or solenoid. The worst thing it could be is a bad exhaust manifold that allowed water into the cylinder. The engine hydro-locked while cranking because the water that entered the cylinder is not compressible. Once the water ran down past the rings, the engine was able to start.

Hard to say which problem you have without more data.

Best regards,
Frank
 
fc3 said:
Might be a lot of different things. Could be wiring, you need to check the cables and connections. Could be a temperature sensitive part like a relay or solenoid. The worst thing it could be is a bad exhaust manifold that allowed water into the cylinder. The engine hydro-locked while cranking because the water that entered the cylinder is not compressible. Once the water ran down past the rings, the engine was able to start.

Hard to say which problem you have without more data.

Best regards,
Frank
Click to expand...

Cables will all be checked tomorrow. I don't think it's hydro lock because the engines were running at idle when I shut them off last night...45 min later no start. Engines are closed cooling...only the risers are exposed to raw water...manifolds get closed coolant.

I'm leaning toward a loose connection...batteries were changed by PO a month ago so a cable is a strong possibility.
 
My guess would be that it wasn't quite exactly in neutral (if V-drives).
 
Hampton said:
My guess would be that it wasn't quite exactly in neutral (if V-drives).
Click to expand...

That was one of my early thoughts as well...but the shifter(s) were not moved overnight. The drives are "direct-straight" but same idea (BW).

Thanks for your thoughts.
 
Check the wires on the slave starter solenoid. One of them is a push on wire. I think it is called an "exciter" wire. Make sure it has a good connection. I had an intermittent start problem caused by this push on terminal being loose.
 
Re: Starter Anxiety 7.4 MPI...update

I spoke with a technician at Marine Power Systems this morning re: no start.

Based on what I told him he said that I either have a neutral safety switch that is beginning to go bad and hanging or the starter is going bad.

He is leaning towards the neutral switch and told me how to jump it to by-pass it if it happens again.

I think I'll pick one up to have on board just in case.

In our shop talk conversation about engines he told me that GM sent the word out that no more new 496/502 engines will be built after 10/09. MPI has told them that no build orders for these engines will be processed after May of this year. I guess with the marine industry as flat as it is, and lack of orders from Merc, Crusader and MPI that it doesn't pay to produce that engine. WTF:huh:

The replacement is a 450 HP/550 Ft. Lb aluminum Cadillac turbo charged V8. The new engine in Bob Tail inboard form only weighs 650 lbs!! Only time will tell how reliable this new engine will be. I remain open minded but somewhat dubious.
 
Sprink
That happened to me once. Some have heard this story before but I'll repeat it for you...

HOT summer day (90+ degrees). Anchored out for about 5 hours after an hour run. Ready to leave but couldn't get the port engine started. No click, no nothing. NEVER happened before and both solenoids were new. Neutral switch was OK. Tried beating the starter (carefully) with a hammer. Nothing. One of my friends came up with the idea of packing the starter with ice. So we did, for about 10 minutes. A couple more judicious taps and she started right up. Got back to the slip, shut down, started, repeated several times w/o incident. We were set to leave for a week long cruise two days later and I didn't want any issues. West Marine had a starter in stock so the next morning, I installed it. Took the old one for a rebuild and installed it on the stbd engine, put the starboard one in storage as a spare.

It was explained to me that sometimes flat spots form inside the starter and if the starter motor happens to stop spinning on a flat spot, the connection is not made. Thus, no start. With heat, there's expansion of the metal so the problem can be enhanced. Sounds weird but the ice thing DID work after nothing working for about 1/2 hour of trying. :huh:
 
QUOTE "He is leaning towards the neutral switch and told me how to jump it to by-pass it if it happens again."

How do you jump the neutral switch? Just by connecting the two wires??:huh:
 
rondds said:
Sprink
That happened to me once. Some have heard this story before but I'll repeat it for you...

HOT summer day (90+ degrees). Anchored out for about 5 hours after an hour run. Ready to leave but couldn't get the port engine started. No click, no nothing. NEVER happened before and both solenoids were new. Neutral switch was OK. Tried beating the starter (carefully) with a hammer. Nothing. One of my friends came up with the idea of packing the starter with ice. So we did, for about 10 minutes. A couple more judicious taps and she started right up. Got back to the slip, shut down, started, repeated several times w/o incident. We were set to leave for a week long cruise two days later and I didn't want any issues. West Marine had a starter in stock so the next morning, I installed it. Took the old one for a rebuild and installed it on the stbd engine, put the starboard one in storage as a spare.

It was explained to me that sometimes flat spots form inside the starter and if the starter motor happens to stop spinning on a flat spot, the connection is not made. Thus, no start. With heat, there's expansion of the metal so the problem can be enhanced. Sounds weird but the ice thing DID work after nothing working for about 1/2 hour of trying. :huh:
Click to expand...

That is an amazing story....very believable. I have to remember that one!!! I come from a family of metallurgist so I can understand the ice deal.

How in the hell are we ever going to be able to predict that happening?:huh:
 
sprink56 said:
The replacement is a 450 HP/550 Ft. Lb aluminum Cadillac turbo charged V8. The new engine in Bob Tail inboard form only weighs 650 lbs!! Only time will tell how reliable this new engine will be. I remain open minded but somewhat dubious.
Click to expand...

Cadillac Marine engine. Now thats cool:thumbsup:

Speaking of Cadillacs, My Cadillac had this proplem. It she was hot the starter needed to be hit a few times electricly. If cold, she'd start right up. I put a new starter and away went the trouble.
If I were you I'd replace the starter and carry tools and a spare.

A northstar Cadillac pushing boats....:smt024
 
How in the hell are we ever going to be able to predict that happening
Click to expand...

You can't. Which is why I ran out and bought a new one, then replaced the port engine starter. My boat has original engines and I bought it in 2004, so I'm guessing the starters are original. And if one goes, the other can't be too far behind. That's what happened with my starter solenoids. The port was bad at sea trial in July 2004, and in Aug 2004, the stbd took a dump. If you have Marine Power than your engines are probably a lot newer than mine, so a starter problem is less likely but still not out of the realm of possibility.
 
Looks Chevy to me. Resembles Cadillac Northstar Just a little bit.
 
sprink56 said:
Cadillac LSA http://www.marinepowerusa.com/Repower/PDF%27s/2009_6200_LSA_MarineBase.pdf

I guess this is the next big thing.:thumbsup:
Click to expand...

Can't be the Northstar engine. That block won't go to 6.2 litres of displacement. That 6.2 is a 16 valve pushrod engine. Northstar is a 32 valve overhead camshaft engine. There is no room in those valve covers for a camshaft, much less the equipment for a 4 valve per cylinder head. It doesn't even look like the Northstar. The water pump is wrong as are the spark plugs, which should be in the middle of the valve cover. This seems to be a blown version of your generic Suburban engine. Nice engine, but Merc won't use it because it's expensive. They prefer their cheaper modified 5.7.

Someone did marinize the Northstar some time ago. I think it was used in a couple of skiboats. Northstar is a nice engine. The newer variants have variable cam timing on both intake and exhaust. It has a nice broad torque curve. Leaning pretty heavily towards the STS with the Northstar V8 for my next car. The V6 is okay, but doesn't have the torque of a V8. Just have to wait for my Navi to die, which should be in the next year or two. I will be surprised if she makes 400,000 miles.

Best regards,
Frank
 
Last edited:
fc3 said:
Can't be the Northstar engine. That block won't go to 6.2 litres of displacement. That 6.2 is a 16 valve pushrod engine. Northstar is a 32 valve overhead camshaft engine. There is no room in those valve covers for a camshaft, much less the equipment for a 4 valve per cylinder head. It doesn't even look like the Northstar. The water pump is wrong as are the spark plugs, which should be in the middle of the valve cover. This seems to be a blown version of your generic Suburban engine. Nice engine, but Merc won't use it because it's expensive. They prefer their cheaper modified 5.7.

Someone did marinize the Northstar some time ago. I think it was used in a couple of skiboats. Northstar is a nice engine. The newer variants have variable cam timing on both intake and exhaust. It has a nice broad torque curve. Leaning pretty heavily towards the STS with the Northstar V8 for my next car. The V6 is okay, but doesn't have the torque of a V8. Just have to wait for my Navi to die, which should be in the next year or two. I will be surprised if she makes 400,000 miles.

Best regards,
Frank
Click to expand...

i think the LSA may be the marine version of the Corvette ZR1/Cadillac XLR V engine.

MPI is supplying these to an offshore power boat racing team this season. If this thing holds together, we may be witnessing a "Paradigm Shift" in high torque marine power.

The big block Chevrolet/GM has been the go to engine in this category for over 40 years....with the bob tail marine versions weighing in at 1150~1200 lbs. vs. 650 lbs for the LSA . If the LSA proves to be reliable it will be a natural for small to medium size cruisers not to mention the Formula/Fountain applications.

I would not be surprised to see Merc offer a version of this power plant in the near future.
 
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