Mercruiser 4.3L EFI hesitates at high speeds

[bluewaterboater]

I have been having some issues for a year now with my engine in my Sea Ray 190 BR. The boat is going into the shop next week to have a go over and I thought I would get some advice here before it goes. The serial number on the engine is 0L092324

The problem:

When I push the throttle all the way down the engine gives off a popping noise and it hesitates. When I ease off the throttle it goes away. Going 35mph or so is not an issue, it only happens on the high end of the speed. This is an intermitant problem and I have had the boat full out in the range of WOT and about 48mph.

What I have done so far:

This is NOT a prop issue. I have a SS 21p prop on and I have also tried a 23p prop and the results are the same. The boat IS propped correctly. Like I mentioned above I have had the boat at WOT and no issues.
Compression has been checked on all 6 and is good.
Spark plugs and wires have been changed.
Rotor and cap have been changed.
Fuel/water separator has been changed.

The boat starts, runs and drives like a dream all the time and has never let me down. My only issue is on the high end of the rpms and speed. When this problem happens my rmp gauge just goes stupid and starts bouncing all over the place but I don't know if this is related to the problem. Could it be the fuel pump? Does a fuel pump work or not or work but not enough fuel?? Could it be the rev limitor acting up prematurely??

Thanks for any help that you can offer

 

[alldodge]

Re: Mercruiser 4.3L EFI hesitates at high speeds

It's possiable the knock sensor is picking up what if thinks is a miss/knock. If this happens it will try to retared the timming. Could also be a loose connection from corrosion. With the tach bouncing could be the result of a bad connection or engine stalling. Look at the routing of the knock sensor wire and it should be kept away from spark plug wires as much as possiable. With it being so intermittent it will be difficult to find.

 

[achris]

Re: Mercruiser 4.3L EFI hesitates at high speeds

Any thing to do with the fuel would not cause the tacho to 'go stupid'. It does sound like the rev limiter kicking in. Have you checked the accuracy of the dash tacho? You may be hitting the rev-limiter, but an inaccurate dash tacho reading low indicates otherwise.

 

[Tail_Gunner]

Re: Mercruiser 4.3L EFI hesitates at high speeds

Post your gearing on your lower leg that may help

1.98 gearing at 5100 rpm 21p nets 50 mph no slip

1.98@5100 23p nets 56 mph no slip

If your gearing is 1.98 guess what your pitch is wrong and a strong 4.3 in a 19 foot boat can do 54mph. So lets correct the pitch to speed 24p gets at 9% slip nets 52. Id check the gearing close, You may want to check you voltage levels out on you altenator...battery etc going into a low voltage situation can produce some strange results.

 

[achris]

Re: Mercruiser 4.3L EFI hesitates at high speeds

Post the serial number of the drive and we can get the ratio from that.

 

[Fun Times]

Re: Mercruiser 4.3L EFI hesitates at high speeds

Post your gearing on your lower leg that may help.

Post the serial number of the drive and we can get the ratio from that.

Let's surprise him a little bit. Here should be his info from new to work with.

ENG: 0L092324 4231017LS MERCRUISER 4.3L ALPHA EFI
DRV: 0L404710 5121400LS MERCRUISER ALPHA 1.81:1
TRN: 0L291264 6111001LS MERCRUISER ALPHA TRANSOM

Side note, He may still have the one piece exhaust system. Chris's favorite.:lol:

 

[achris]

Re: Mercruiser 4.3L EFI hesitates at high speeds

Let's surprise him a little bit. Here should be his info from new to work with.

ENG: 0L092324 4231017LS MERCRUISER 4.3L ALPHA EFI
DRV: 0L404710 5121400LS MERCRUISER ALPHA 1.81:1
TRN: 0L291264 6111001LS MERCRUISER ALPHA TRANSOM

Side note, He may still have the one piece exhaust system. Chris's favorite.:lol:

Well, his data says he's in Ontario, so unless he's WAAAAY north and running in Hudson Bay he's likely to be in one of the Great Lakes, freshwater. Not so much of a problem for the one piece, but I'd still like to see them gone...

Surprised me a bit to see 1.81 as the ratio, especially in a small boat (19ft.) It's quite a bit lighter than my boat and with the (1994) 4.3LX I was running a 21" and still getting to 5100 rpm (that drive was also 1.81). Given that, I would expect the 23" prop to be the right one, with a top speed in the area of 50 knots (63mph)...

Chris....

 

[bluewaterboater]

Re: Mercruiser 4.3L EFI hesitates at high speeds

Let's surprise him a little bit. Here should be his info from new to work with.

ENG: 0L092324 4231017LS MERCRUISER 4.3L ALPHA EFI
DRV: 0L404710 5121400LS MERCRUISER ALPHA 1.81:1
TRN: 0L291264 6111001LS MERCRUISER ALPHA TRANSOM


Side note, He may still have the one piece exhaust system. Chris's favorite.:lol:

WOW you're good that is exactly what I have! And yes most of our boating is in Lake Ontario, Lake Erie and the Trent Severn. From what I know its all original equipment with the boat and the original factory prop would have been a stainless steel 21p prop. this is what i have on it and i have a 23p aluminum as a backup.

Yesterday we were out in some pretty rough water so I was not able to go full out by any means BUT when I throttled heavy to push through a wave the popping sound would happen. It seems that under very heavy load is when the problem happens.

Keep in mind with the prop sizing that the boat is about 3,000 pounds empty and with my gear and family we easily add 800 pounds to that.

Thanks!

 

[bluewaterboater]

Re: Mercruiser 4.3L EFI hesitates at high speeds

Well, his data says he's in Ontario, so unless he's WAAAAY north and running in Hudson Bay he's likely to be in one of the Great Lakes, freshwater. Not so much of a problem for the one piece, but I'd still like to see them gone...

Surprised me a bit to see 1.81 as the ratio, especially in a small boat (19ft.) It's quite a bit lighter than my boat and with the (1994) 4.3LX I was running a 21" and still getting to 5100 rpm (that drive was also 1.81). Given that, I would expect the 23" prop to be the right one, with a top speed in the area of 50 knots (63mph)...

Chris....

Chris,

The fastest I can recall having the boat with my 21p prop and a couple people in the boat was 49mph. This was the occasional time when it wasn't acting up like it is now. That was on gps. Its a pretty heavy boat that's at least true 19' with 8.5' width and very deep.

Thanks!

 

[achris]

Re: Mercruiser 4.3L EFI hesitates at high speeds

I think you're now at the point where you need to get a diagnostic scan tool or computer based software involved. Your engine has the MEFI1 ECU and you need to be able to read any trouble codes, and for that you need the right tools.

Chris........

 

[Tail_Gunner]

Re: Mercruiser 4.3L EFI hesitates at high speeds

I would verify the tach within 200 rpm....with a 1.8 drive a 21p prop would hit the limiter in that boat...I could hit the limiter with 1.66 with a 21..19' 2850 deep v

 

[bluewaterboater]

Re: Mercruiser 4.3L EFI hesitates at high speeds

Here's an update so far: Brought it to the marine mechanic and he did some checking on land. Checked the fuel pump and system and it checked out perfectly, lots of pressure. He also hooked it to his computer and there were no faults whatsoever. He is going to take it for a water test in the next few days to get a feel for what is happening. He is concerned it may be an engine issue like the lifters hanging up or something like that.... I hope not. He will report back to me after the water test.

I did speak with him about the 21p prop and my 23p and he is very convinced i am not hitting my rev limiter.

 

[bluewaterboater]

Re: Mercruiser 4.3L EFI hesitates at high speeds

It looks like the problem is solved!! :joyous: My mechanic took the boat for a test run and ruled out the lifters, he thought for sure it was a fuel issue since the motor was giving off a "lean pop". After the test run he went through the whole fuel system, cleaned the antisyphon, changed the fuel/water separator, blew out the hoses, cleaned any other filters that have anything to do with fuel system and also replaced the cap and rotor. Took it for another good test run and it ran great!!

He said he didn't believe it was any specific piece that was causing the issue but more like all the dirty components together caused the issue. Even though i replaced the fuel/water separator, cap and rotor last year he felt that I had put enough hours on the boat (about 40-50) in one season that they should all be replaced.

 

[alldodge]

Re: Mercruiser 4.3L EFI hesitates at high speeds

Glad your running, but sounds like the dealer mechanic that worked on my boat, he shotgunned everything and fixed it for the time being. Sure wish we had a mechanic which was as good as he/she thought they were.

 

[bluewaterboater]

Re: Mercruiser 4.3L EFI hesitates at high speeds

Update #2 - we took the boat out this weekend and it performed great.....well for about 6 hours :grumpy: after that we took it for a long run and at about 42 mph it started to do the popping sound again. It hadn't done this all day even at speeds up to 50mph and out of the hole pulling 2 - 3person tubes. It did perform way better than it has in the past but we still have some work to do.
I talked with the mechanic this morning and he is certain its a fuel issue since the work he did had made it better.

Is it possible that there is sediment in the plastic fuel tank that is getting caught up in the filters and clogging a little? I don't know the history of the boat for the first 13 years of its life. after he cleaned my fuel system could it clog a small percentage and lean out my engine a bit at high speed?

Remember earlier in the day it ran like a champ and it still runs better than it ever has. Any suggestions?

 

[alldodge]

Re: Mercruiser 4.3L EFI hesitates at high speeds

Update #2 - we took the boat out this weekend and it performed great.....well for about 6 hours :grumpy: after that we took it for a long run and at about 42 mph it started to do the popping sound again. It hadn't done this all day even at speeds up to 50mph and out of the hole pulling 2 - 3person tubes. It did perform way better than it has in the past but we still have some work to do.
I talked with the mechanic this morning and he is certain its a fuel issue since the work he did had made it better.

Is it possible that there is sediment in the plastic fuel tank that is getting caught up in the filters and clogging a little? I don't know the history of the boat for the first 13 years of its life. after he cleaned my fuel system could it clog a small percentage and lean out my engine a bit at high speed?

Remember earlier in the day it ran like a champ and it still runs better than it ever has. Any suggestions?

That would be No; the plastic line is only an indication if you fuel pump diaphram goes out. If the diaphram goes out you will see fuel being pumped in the line going to the carb which causes a very rich mixture. Usually causes it to die. If no fuel is there your pump is not leaking, may not be pumping sufficient pressure but it is not leaking

 

[zildjian29]

Re: Mercruiser 4.3L EFI hesitates at high speeds

I was having the same issue with my mercruiser 3.0! It would hesitate at wot kinda like it was miss. And my tach would bounce all over. Mine ended up being a bad wire from tach to coil. Also kept burning my points up cause the wire was messing with the coil. Anyways maybe check the resistor wire to coil.

 

[CharlieB]

Re: Mercruiser 4.3L EFI hesitates at high speeds

Checking fuel pressure in the shop with NO LOAD cannot show a fuel problem. Load greatly increases fuel demand, flow is keky.

Rig a fuel pressure gauge and check pressure under load at WOT, if not within spec then you need further checking into the fittings and pump, any restriction can contribute to reduced output and the motor begins to go lean, causing a lean pop.

Running lean at WOT also increases combustion temps. until the pistons melt.

 

[zildjian29]

Re: Mercruiser 4.3L EFI hesitates at high speeds

You should also check the resistance going to the coil for your tachometer problem. Is the coil getting super hot? Just a thought! Could be a combination of fuel related and ignition related. I thought mine was fuel I tried everything and everything I did would help a little until we changed the wire and it was fixed.