Hard spot while cranking

[SanJuanDreamer]

My port engine is a 1998 454xLs TBI with 1450hrs.
Lately, when starting the Port engine, it'll crank fine but at a certain point in the cranking cycle, it'll almost come to a stop, then resume cranking and when it come that spot again, it'll almost stop....the engine will start but seems it has a miss for almost a minute and then run fine. I'm sure its not starter but maybe a hard spot in the cranking process.

Hope that makes sense...your thoughts?

[bud37]

Check the positive lug on the starter, make sure it is clean and tight.Battery voltage as well......

[SanJuanDreamer]

Update.
Spoke with a Mec who does Crusaders.
He said it might be the riser leaking into the head, pooling on values, probably exhaust.
We'll do a compression check and leak down and see where it goes.

[Viper]

Source of the post....He said it might be the riser leaking into the head, pooling on values, probably exhaust.....

My thoughts too providing the electrical system and starter have been ruled out.

Source of the post....We'll do a compression check and leak down and see where it goes.

I don't see how that is going to tell you anything about a leaking exhaust system. You don't have to have bad valves or poor compression for this to happen. If the manifolds, risers or elbows are leaking, the water can simply enter an exhaust valve that's in the open position in it's cycle. I think they're barking up the wrong tree here unless they suspect an engine related problem. If they suspect a leaking exhaust system, they need to pressure test it.

You could eliminate the exhaust as the culprit by simply disconnecting the raw water to it, direct the hoses to the bilge because this will get messy, drain the raw water from the exhaust, run the engine for a few seconds, then shut it off. Wait the normal amount of time you think it takes before this symptom arises; an hour or two or overnight, then start the engine again. There is no water in the exhaust this time to leak back so if the engine is hard to crank again, the problem is not due to a leaking exhaust system. If it starts easily, it's likely that raw water is leaking from the exhaust side of one of the exhaust components.

Looks like you're a salt water application. Are the manifolds closed cooling (coolant)? When was the last time raw water exhaust components were replaced? Typically, in salt water, the raw water exhaust components are on borrowed time after 5 years. When the passages rust through, you could have a minor problem such as you're describing or a serious engine failure.

[SanJuanDreamer]

On the cooling system, it starts off coming through the strainer, then it goes through the V-drive, to the raw water pump, through the trans U cooler, into the HE and then goes out through the top of the exhaust upper riser....simple cooling system, not a lot of saltwater exposure. There is a blocking plate between the manifold and upper exhaust riser. Its the blocking he was mentioning. When the motor stops, there is always a little bit of water left in the upper exhaust riser. That pooled water maybe dripping past the blocking plate into the intake or exhaust side on the motor.

They were replaced in 09, but my thought is its only connected to the top part of the exhaust riser, so replacing exhaust system should be off in the far distance.

I believe most cooling systems will connect the outgoing saltwater to the lower part of the manifold and the water will make its way to the upper exhaust riser, in this case, saltwater doesn't go through the manifolds, just the top of the upper exhaust riser.

[Viper]

Source of the post .... There is a blocking plate between the manifold and upper exhaust riser. Its the blocking he was mentioning. When the motor stops, there is always a little bit of water left in the upper exhaust riser. That pooled water maybe dripping past the blocking plate into the intake or exhaust side on the motor.....

It's possible it's leaking there but the block-off plate isolates the fresh water side (coolant) from the raw water side. The only way water will get into the exhaust is if it leaks between the riser and the block-off plate where they meet. This can happen if the riser's mating surface is really rusted and not making a good seal, or, the riser or elbow cooling passages are rusted through to the exhaust side.

Source of the post....not a lot of saltwater exposure......

If the blocking plate is between the manifold and the riser as you described, you actually have full salt water flow in your riser and elbow, so it is a lot of salt water exposure there.

Source of the post ....They were replaced in 09, but my thought is its only connected to the top part of the exhaust riser, so replacing exhaust system should be off in the far distance......

If it's been running that long in salt water, the risers and elbows are on borrowed time. Because of the block off plate, salt water will always sit in the riser's water passage as it has no place to drain. That's a perfect setup for rusting through the walls. Your manifolds are closed cooled so they'd be okay but top part or not, if the risers rust through from the cooling passages to the exhaust side, you will get salt water in your engine. Even if they are not currently leaking, if I were working on your boat, I'd be recommending riser and elbow replacement given their age in salt water.

[Viper]

I got so tied up in the possible leak that I completely forgot about the last time I ran into this! Did they check the timing? Improper timing can also cause the same symptom. Timing was the cause when I last ran into this issue in the Spring. Was off a couple of degrees and once corrected, the symptom never happened again. It was a Crusader engine but carbed though that difference shouldn't matter. It's an easy check before you start tearing things apart.

Also check the battery and connections as mentioned above.

[SanJuanDreamer]

I'll check...
But how could a timing issue go away after 30 to 45 seconds of running?
After that time, it runs as if should.

[Viper]

The timing issue doesn't go away, once the engine starts, it's just easier for it to deal with but make no mistake, it's not running at optimal performance and could have dire consequences. The one I worked on ran seemingly fine in a sea trial after the hard start also. What you're describing is exactly what the owner of the boat I worked on reported too. This was an on-going issue he had after a re-power. Because it was a re-power, I assumed the folks that installed it set it up properly so I focused on other areas such as batteries, wiring, the starter, and water ingestion. After ruling those out, I checked timing, re-set it, problem solved. There are other things that can contribute to this symptom but don't rule out the timing, and because it's such an easy thing to confirm, it'll be the least time consuming and the least costly.

[SanJuanDreamer]

Update - while changing the exhaust system on the Port motor, the shop needed to remove the engine to get to a manifold.
While they were working on it, they noticed the "Drive Dampner Assembly" had a missing spring.
It was mentioned the missing spring would be the casue for the hard cranking and vibration\miss in that motor.
Also, that spring was just bouncing around in there while the motor was running......
When I get it back, I'll be testing to make sure that's the cause.

Also, the compression\leak down showed mid 140's with one coming in at 138.
I beleieve 150 - 155 is optimal...not bad for 1490hrs on each motor.