99 502 help 760 hrs

[Andy B.]

Hey guys was coming in yesterday and motor sounded a little flat if that makes sense lol. It would only hit 4400 rpm good oil pressure and water temp gauge normal 160 usually can rev to 4950-5000. I pulled all 8 plugs no water in any of the cylinders a couple plugs looked a little lean. I pulled the plugs because I have white water steaks on my EMI top of header so I thought maybe a little water but none. Plugs are 7 years old .

 

[Runs2rch]

Get new riser gaskets. Start by pulling and inspecting.

 

[ElAzul]

7 year old plugs? I would start with an overdue tune up and go from there lol

 

[Carrera205]

Compression test?

 

[Andy B.]

That will be next don't have the gauge to screw in plug hole. New rotor and cap 7 years ago I went ahead and got new plugs. If I have low compression in any cylinder will it hurt to run it nothing hire than 3500 I can still cruise at 45 ? My mechanic can't get it in until the 29th he's crazy busy which I'm happy for him.

 

[Runs2rch]

That will be next don't have the gauge to screw in plug hole. New rotor and cap 7 years ago I went ahead and got new plugs. If I have low compression in any cylinder will it hurt to run it nothing hire than 3500 I can still cruise at 45 ? My mechanic can't get it in until the 29th he's crazy busy which I'm happy for him.

Take it to Gerry's Marine in Henderson. Good people there.

 

[Andy B.]

Take it to Gerry's Marine in Henderson. Good people there.

Thats my mechanic booked until the 29th.

 

[Bobby V]

Its the media's fault for the leak.

 

[Runs2rch]

Thats my mechanic booked until the 29th.

Brian did say they were busy. I wouldn't think until the end of May. Wow.

 

[Your ad here]

Fuel filter condition? How is the alternator voltage? We had a weak alternator in our jet bote. Installed a new one and swear it made a 30hp gain.

 

[Andy B.]

Fuel filter condition? How is the alternator voltage? We had a weak alternator in our jet bote. Installed a new one and swear it made a 30hp gain.

between 12-14 volts on the gauge normal also. On the full service is that part of it I get it done every year i'll check my invoice thanks.

 

[Andy B.]

Just checked invoice yep new fuel filter Doing compression check tomorrow whats the best gauge to get ?

 

[Ragged Edge]

What ever your local auto parts store has. You won't be using it every day so it does not have to be professional grade. If I remember right with your motor your looking for 150 to 160 psi. Anything below 100 psi is a dead hole, below 110 it's really not doing much.

 

[Andy B.]

What ever your local auto parts store has. You won't be using it every day so it does not have to be professional grade. If I remember right with your motor your looking for 150 to 160 psi.

Thanks yes thats what the book says I haven't done a compression check on a motor since I was 14 helping my brother rebuild his 428 CJ in his 70 Mach 1. Shit was so simple back in the late seventies....................

 

[Andy B.]

If compression is good i'm going to run it Friday will sty close to ramp hang out around swallow.

 

[guest hs]

Pull the cap and rotor look for green color on the terminals replace the plugs do a compression test go from there

 

[Andy B.]

Pull the cap and rotor look for green color on the terminals replace the plugs do a compression test go from there

If green new cap and rotor got new plugs already and thanks,

 

[Riverryder]

@Andy B. Call envy marine in boulder. I toke my boat to gerrys to get its service cause someone I work with uses them. He looked it over “with a fine tooth comb” didn’t tell me a ram is leaking, didn’t change my air filter called him to see about the gas issue and he was a prick.
Sent my brother to envy and he fixed his boat and is now going to fit me in to not ruin my weekend. Oh and he had beers to share with my brother and his wife for after hours shooting the shit.


Sent from my iPhone using Tapatalk

 

[Andy B.]

UPDATE: compreven pretty even on all cylinders one was 7=10 psi higher new plugs rerouted some battery cables to my standers cap and rotor good added some Lucas injector cleaner was a little worried about the spark plug gap but mechanic said pretty close from factory.

It started right up and purrrrrred cranked over better than ever still need to replace gaskets on elbow and going to go head and replace the one on manifold also notice minute 1/4" white trail hitting lake tomorrow will give update.

On another note I have your basic tools what would it take to get everything so I can do my yearly service and pull the drive every couple years enjoying working on a motor again!

 

[SBMech]

UPDATE: compreven pretty even on all cylinders one was 7=10 psi higher new plugs rerouted some battery cables to my standers cap and rotor good added some Lucas injector cleaner was a little worried about the spark plug gap but mechanic said pretty close from factory.

It started right up and purrrrrred cranked over better than ever still need to replace gaskets on elbow and going to go head and replace the one on manifold also notice minute 1/4" white trail hitting lake tomorrow will give update.

On another note I have your basic tools what would it take to get everything so I can do my yearly service and pull the drive every couple years enjoying working on a motor again!

You are looking for 10% across the board. So if you had a baseline of 150 PSI then you could have a variance of 15 PSI either lower of higher and be within specifications.

If you got 130,140,135,130,150,(110),130,125, then you would be looking at a possible issue with the low hole...you need to make at least 90 PSI to fire a cylinder.

IF no one told you, this test should have been performed with all plugs out, full throttle with coil disabled, and around 10 compression "hits" per cylinder.

 

[boatdoc55]

You are looking for 10% across the board. So if you had a baseline of 150 PSI then you could have a variance of 15 PSI either lower of higher and be within specifications.

If you got 130,140,135,130,150,(110),130,125, then you would be looking at a possible issue with the low hole...you need to make at least 90 PSI to fire a cylinder.

IF no one told you, this test should have been performed with all plugs out, full throttle with coil disabled, and around 10 compression "hits" per cylinder.

Damn SB. You sound like you know what you're doing!!!!!!

 

[Andy B.]

You are looking for 10% across the board. So if you had a baseline of 150 PSI then you could have a variance of 15 PSI either lower of higher and be within specifications.

If you got 130,140,135,130,150,(110),130,125, then you would be looking at a possible issue with the low hole...you need to make at least 90 PSI to fire a cylinder.

IF no one told you, this test should have been performed with all plugs out, full throttle with coil disabled, and around 10 compression "hits" per cylinder.

Had coil wire pull didn't have full throttle should I redo it?

Thanks for the response!!!

 

[Runs2rch]

Had coil wire pull didn't have full throttle should I redo it?

Thanks for the response!!!

Its probably fine. You are only down a few hundred rpms. I bet the stock white rotor is the issue. They are inferior to begin with. Then get play. How old are the wires?

I would do plugs, cap, rotor, and wires depending on age. Run NGK bpr6fs instead of the br6fs. Projected tips will last a little longer, and burn a little cleaner. you will notice a cleaner transom.

 

[Andy B.]

Its probably fine. You are only down a few hundred rpms. I bet the stock white rotor is the issue. They are inferior to begin with. Then get play. How old are the wires?

I would do plugs, cap, rotor, and wires depending on age. Run NGK bpr6fs instead of the br6fs. Projected tips will last a little longer, and burn a little cleaner. you will notice a cleaner transom.

Rotor and cap only 5 years old has been replaced along with coil, already installed the plugs next time NGK I have mufflers so transom stays clean.

Thanks!!

 

[Trash]

I can almost guarantee your injectors are leaning out. Time to have them cleaned and flow tested. Motor laying down on the big end while appearing normal everywhere else is a strong indicator of ill flowing injectors. Have the injector baskets cleaned too or replaced.

As an aside, I would also recommend going back to the original Merc spark arrestor. Nearly every aftermarket version impacts WOT hp to a significant degree. OSO has some great dyno threads regarding this.

 

[Andy B.]

I can almost guarantee your injectors are leaning out. Time to have them cleaned and flow tested. Motor laying down on the big end while appearing normal everywhere else is a strong indicator of ill flowing injectors. Have the injector baskets cleaned too or replaced.

As an aside, I would also recommend going back to the original Merc spark arrestor. Nearly every aftermarket version impacts WOT hp to a significant degree. OSO has some great dyno threads regarding this.

Cap rotor,coil and spark plugs are all merc recommended (stock)and will have the injectors cleaned when and tested on the 29th thanks!!

It's crazy it happened so sudden running great all year have had it out 8 times this season!

 

[Trash]

Cap rotor,coil and spark plugs are all merc recommended (stock)and will have the injectors cleaned when and tested on the 29th thanks!!

It's crazy it happened so sudden running great all year have had it out 8 times this season!

Referencing my spark arrestor comments, I mean the flame arrestor. The stock Merc one flows the best. Aftermarket ones perform quite poorly on these motors. Not that this has anything to do with your current RPM issue. It was simply a side-bar comment.

Good luck and let us know what you find.

 

[ElAzul]

Referencing my spark arrestor comments, I mean the flame arrestor. The stock Merc one flows the best. Aftermarket ones perform quite poorly on these motors. Not that this has anything to do with your current RPM issue. It was simply a side-bar comment.

Good luck and let us know what you find.

I put mine in a 5 gallon bucket with aome some hot water, degreaser was pretty surprised how much crud and muck was left behind after cleaning. Some people like to take a wrap or two off for more air flow on the aftermarket one's but I wouldn't want the liability with insurance on a claim if something happened

 

[Andy B.]

I put mine in some hot water degreaser

Do you have a pic of it?

 

[ElAzul]

Do you have a pic of it?

Mine is what I have

 

[rrrr]

I put mine in a 5 gallon bucket with aome some hot water, degreaser was pretty surprised how much crud and muck was left behind after cleaning. Some people like to take a wrap or two off for more air flow on the aftermarket one's but I wouldn't want the liability with insurance on a claim if something happened

Your better believe insurance investigators will go over a boat fire or explosion closely, and if they find the flame arrester has been tampered with or discarded, they aren't going to pay a claim.

 

[Runs2rch]

Cap rotor,coil and spark plugs are all merc recommended (stock)and will have the injectors cleaned when and tested on the 29th thanks!!

It's crazy it happened so sudden running great all year have had it out 8 times this season!

Lavey 29 on here, John Mosetti Boats Unlimited sells a much better than oem injector for the 502 MPI. Give him a shout. He also cleans, and flow tests.

 

[Andy B.]

Lavey 29 on here, John Mosetti Boats Unlimited sells a much better than oem injector for the 502 MPI. Give him a shout. He also cleans, and flow tests.

Thanks boat ran great today maybe bad gas put some Lucas injector cleaner in it also let that sit in the gas tank overnight I'm sure the new plugs helped.

I've never had injectors professionally cleaned so definitely doing that back up to 4900 rpm.

Is he here in Vegas?

 

[buck35]

John is in the Dallas area.

 

[Runs2rch]

John is in the Dallas area.

Arlington right?

 

[buck35]

Maybe so . I bought a set of Merc manuals from him a few years ago .really nice guy and one smart cookie!

 

[Trash]

Thanks boat ran great today maybe bad gas put some Lucas injector cleaner in it also let that sit in the gas tank overnight I'm sure the new plugs helped.

I've never had injectors professionally cleaned so definitely doing that back up to 4900 rpm.

Is he here in Vegas?

You can have your injectors cleaned and flow tested at many locations. Doesn't have to be marine specific. They just need the right equipment. They should label the injectors 1-8, flow test them before and afterwards showing the difference. They should be flow balanced too with comments on spray pattern.

 

[Andy B.]

You can have your injectors cleaned and flow tested at many locations. Doesn't have to be marine specific. They just need the right equipment. They should label the injectors 1-8, flow test them before and afterwards showing the difference. They should be flow balanced too with comments on spray pattern.

Thanks!

 

[guest hs]

Thanks!

Andy, J/S Diesel will do your injectors in Vegas

 

[Andy B.]

Thanks Shane!!