90 SN 351 idle problem

Shoot me an email: TRBenj@gmail.com

I don't think you need to be worring about a rebuild at this point. Replace the oil with what's recommended (probably 20W50) and you should be fine (and keep gasoline out of the crankcase).
I'd suggest learning to work on it yourself. It's not all that hard and it saves a lot of time and money, most of the time. Plus it gives me a good feeling to fix things myself.
As far as troubleshooting:
--Work on one commponent at a time
--Have a reason for fixing that component
--Take a systematic approach
--Eliminate the simple/obivious things first (most problems are the simple/obivous or they started out that way and messed up other things)
The fourm is a great resource.

an idle issue will not effect an oil pressure issue, if you don't have a good oil pressure at 2000 and a bad idle, your not going to have good oil pressure at 4,000 rpm or 1000 rpm. Keep telling your self it's going to fix it's self. All of the suggestions are band aid's mine included, to get you a little more time but the bottom line is the motor is junk and needs rebuilt, keep telling your self it's ok and when the rod shoots out the side of the block, while your being towed in, call me and I'll remind do you remember.....

Kylecraft,
Just stick with it a while longer and you'll be skiing in no time. You've stated you have a solid hull and new tranny to say the least so your almost there.

A Carb re-build is great when you do it yourself. If you pay a mechanic then the labor plus the kit is probably more than a new Edelbrock Marine carb.

If you really like your hull and the boats performance then rebuild that engine. If you need help talking to the machine shop, drop me an email and I'll call them with you.

Regarding the engine, very few Dealers dig into the internals and repair them and the result is they can offer little or no help with the oil pressure issue. I always check around and find a machine shop that is fully equipped to pull the engine, tear down and bore and re-assemble. Find one that does performance engines. Most Dealers/Mechanics will send the engines or maybe just the block and heads to the same place and reassemble themselves, but pay the machine shop to reassemble is only about $200 and now you have only the machine shop to deal with. If you just teardown, replace all bearings and gaskets the total price should be around $1200. Takes about a week. Boring adds no time, but the last one I did cost me $150 to bore and I bought forged pistons for about $240 bringing my total to around $1800. The shop pulled the engine on Monday and had me skiing on Friday.

You can buy cheaper pistons but make sure the piston to cylinder wall clearance is 0.40" or you'll be right back on this forum. I went with forged since several of us slalom at 36 MPH and 3600 RPM for long periods of time. Cruising and Wakeboarding don't require this attention but if you've got the $'s it's money well spent.

By Performance I'm refering to guy's that machine during the day and possibly race on weekends. These guy's can rebuild a Holley and check all circuits in their sleep and the finished engine will have equal compression (as close as can be measured) in every cylinder. These style shops are all over and the guy's who work them are well experienced for rebuilding a performance marine engine. If you bore, you have a great chance to increase compression which IMHO is a great way to begin performance modifications. Just stay under 180 psi and you can still run pump gas.

Good Luck

newsflash.

so got the carb rebuilt. it now runs worse than ever (virtaully no oil pressure) and it cost me 600 bucks. I don't have very much money and my one passion is skiing.

writing this is tough, I don't know what to say...

all I want is someone who knows what the hell they are doing to tell me how to fix this boat.

I appreciate what everyone has done on this site, unfortunately none of you are close to me.

The biggest problem I have now is the boat is in the water; I didn't have time or a truck to pull it out and take it somewhere else, wherever that even is... I don't know who to trust with this thing. So I have to wait until next weekend to pull it out. At least that gives me some time to think about how I'm going to handle it.

My incling is to phone all the marinas close to me and talk to them about it. There is 1 mastercraft dealer but they obviously don't use pcm motors. I won't take it to the CC dealer as I mentioned in earlier posts because it was the worst experience of my life dealing with them last year. I don't know how they are in business other than the fact that they service a rich area and rich clientelle.

what should I look for in a mechanic, to work on this boat? anyone that you guys would recommend in central ontario?

any other causes other than rung out bearings for the low oil pressure.

it doesn't happen until you run it for 20minutes and it has to be a cold motor for you even to get decent psi.

It didn't do this earlier in the year. I've only put a few hrs on it this season.

Thanks Jimbo.

1. it still stalls at idle. Carb kit was installed, but the mechanic mentioned something about a front end kit???? I thought a carb rebuild was a carb rebuild? I could've put a new carb on for the price I paid him.

EDIT: The oil pressure is lower than it was before the kit was put in. When hot it idled below 10psi on the guage and at 30mph will be up around 15. so it is worse than before.

2. he took the boat out himself and adjusted it in the water. He said it ran great until about 20minutes, which is approximately the time it takes to warm up completely. He said he adjusted it but how well I don't know.

3. he changed the oil without me asking for the same reasons you all mentioned. I don't know what he put in; probably 10w30, but I will confirm. I will also confirm the proper filter. I bought a jug of 20w50 so I can swap it out easy.

How do you check the pressure with a manual guage? and who can I take it to to dial in the carb. I don't have a manual and I'm not taking it back to the guy that just did it. For $600 and $500 in labor you should be able to get to the bottom of virtually any and every problem IMO.

I have to find a good mechanic!!!! would any good ford mechanic be able to work on this boat. what should an auto mechanic know about this setup that would be different (rotation, etc.)?

thx
Kyle

79nautique wrote: Odds are it's not 20w50 oil and odds are the mechanic's a dumb ass, and for $1100 you better sue the guy or make him fix it because it's not right and you got screwed, did you know he was going to charge you that much up front? If you did that was pretty stupid to allow him to do it, all you did is get ripped off. If a mechanic doesn't want to work on something them they will give you an extremely high quote in the hopes that you go some where else, but if you bit then your not too smart concidering a carb kit cost $40.00 or less and even if you bought everything to replace on the carb you still have less than 100 bucks in parts. Bottom line your motor is smoked and has to be re-built to fix your problems. I've done this a long time and I told you not too dick with the carb, but did you listen, doesn't sound like it, and it doesn't sound like you believe the only way to fix your problem of low oil pressure is to re-build or re-place the motor. So waiste some more money and by the time yopu figure out I was right and you add up the money you have spent you could have had the motor re-built and been skiing. It sounds like you have spent 1100.00 already and thats have of the price of a short block. So hope you get it figured out because you obviously don't want to listen to us.

easy tiger. re-read my post. I don't know where you came up with 1100. but anyways I still spent too much.

I gave this mechanic 1 shot and it didn't work. Now I need someone who can fix it.

he did rebuild the carb and also installed a new tach for $600 CAD - we have 14% tax, either way its too much and the problems are still there.

I don't need you ramming my stupidity down my throat. but for someone on the internet to tell me i need to rebuild my motor without even looking at it is pre-mature IMO. Not saying you're wrong, but the problems are bigger than just low oil pressure. Not to mention the oil pressure was fine until a few engine hours ago.

I would love to just pull the motor, sell it for scraps and throw a new one in. but I don't have 8 grand to put into a boat worth 15. Even if I threw a new block in it would still have idle problems.

back to my last question: anyone know a good mechanic in ontario or what to look for in one?
thx

EDIT it was $600 total $200 in parts $400 in labor I just relooked at my reciept. $75/ shop hr. 14% tax. not a rip off but not a deal. The mechanic has worked on all kinds of my stuff, but he mainly does outboards and snowmobiles. I've never had a problem with him, but he obviously doesn't know how to work on this boat. i need someone who can!!!!

Kylecraft wrote: <snip> 2. he took the boat out himself and adjusted it in the water. He said it ran great until about 20minutes, which is approximately the time it takes to warm up completely. He said he adjusted it but how well I don't know. <snip> Kyle

Ok, something in the qoute above got me thinking outside the box. Could the problems be electrical related? Mech said boat ran great for 20 minutes, then everything went to hell. Maybe something or a connection in the electrical system is getting hot due to a poor connection and screwing with the ignition system and oil pressure gauge. So, check all the electrical connections at the gauges and the engine. Especially pay attention to the engine/boat wire harness connector (black rubber).

Now, I tend to agree with 79Nautique that bad bearings are the mostly likely cause of actual low oil pressure. However, such a result is usually slow and does not just happen over several engine hours of operation. I guess what I am saying is that something less obvious might be happening...like electrical.

Definately make certain that you have 20w50 in the engine then do not worry about the oil pressure any more...nothing more you can do. Then you must get it running correctly all the time. If it continues to run poor after 20 minutes from cold, something else is going on other than the condition of the engine. Find that problem, then maybe the oil pressure gauge will read correctly and your problems will be gone. I do like the idea of using a manual oil pressure gauge for peace of mind.

Good luck and do not give up. The Ford/PCM 351 engine is about as simple as you can get. Electrical and fuel are usually what gives people headaches due to the harsh marine environment. So look toward electrical.

thanks for the responses guys.

I'm not a mechanic, but not an idiot either. I've had crank bearings go in my 2strokes before and you notice it over time; slowly. My oil pressure issue is new (2-4 engine hrs) which is why I'm hesitant to throw in the towel just yet, but I know a rebuild is in this motor's future. Its just hard for me to believe that it happened this fast.

I will throw a mechanical guage on the oil sender, or would a new sender do the same thing?

Could heat be getting to the sender and causing it to loose its strenght? I don't notice any rattling or grinding which is why I'm hesitant to pull the motor just yet, but as stated I need someone who knows WTF they're doing to look at it, and more importantly with the right tools. I don't have a pressure guage or other auto tools so its tough for me to find the problems.

The mech that did the carb suggested that maybe the idle issue was being caused by the fuel line leaking air; he suggested a new float bowl on the carb. I have had gas drip from where the line comes in and I just give the bolts a 1/8 turn and it stops.

thanks guys

Don't just change the sending unit. The only way to find the real pressure is to use a mechanical gauge. I'm not sure what they cost (maybe around $30). You may be able to borrow or rent one from an auto parts store or shop. Go out in the boat; let it warm up. Unscrew the sending unit and screw in the gauge. Turn off the engine to do this of course. It's pretty easy.
I really think you have two separate problems here. I recommend working on one then the other.
RE: the idle. Any chance you have an exhaust leak? Does the idle improve with the cover open?
By the way, isn't there some 60-something year old guy in your neigborhood or your parent's neiborhood or somewhere that used to work on is own car? Strike up a conversation with him and if it seems like he knows his stuff, tell him what you got going on and ask him if he'd be able to go out on the boat with you and take a look. It would make his day and you'd learn a lot. Just check with us before you start installing a bunch of automotive parts.

Any updates?

So... turns out the oil pressure is fine (whew!) just bad electrical like many mentioned. compression is good with no bad holes. carb was not set up right ever so they've adjusted the throttle, mixture screws and idle speed correctly. They are waiting on a new distributor as they believe the old one was the root of the problem. Nothing wrong with the timing, but due to moisture and heat it would throw off the timing after running for a while. so a whole new distributor is going in and I should have it this weekend to test.

If all goes well and it runs properly I am selling it. I haven't had it out more than 10hrs and I'm just sick of this boat and if anything ever goes wrong with it again I may start at it with an axe. Its worth more to someone else than me right now. If you don't mind coming to the Toronto, ON area let me know this boat is for sale pending a water test (even if the test is not good I will fix it to sell it).
thanks for all your help,
Kyle