low oil pressure 1990 351

**bobchris** · 07-11-2006, 07:59 AM

RE: low oil pressure 1990 351

what weight oil are you using? but you most likely need to re-build the engine because your bearings are shot.

**MiracleDriver** · 07-11-2006, 08:33 AM

RE: low oil pressure 1990 351

10w30 quaker state synthetic

**TRBenj** · 07-11-2006, 09:34 AM

RE: low oil pressure 1990 351

That is fairly light oil, even for Canadia. Id go with 15w40, 20w50 or straight 40w if you can find it.

Are you sure your sending unit/gauge is accurate? I assume this is a new problem? I certainly get lower oil pressure at idle than running, but if youre getting 20psi max thats not a good sign.

**bobchris** · 07-11-2006, 09:44 AM

RE: low oil pressure 1990 351

flush the syn crap and but in 20w-50 and see if you get an extra 10 lbs of pressure if you don't then it's going to let go pretty soon, so I would baby it and re-build the motor this winter.

**MiracleDriver** · 07-11-2006, 11:39 AM

what does it take to rebuild the bearings? I had a comp test last summer and it was top notch according to the mechanic.

I'm assuming I have to pull the motor out and the crank to get at the bearings. How much would it run me to have someone do this? maybe swaping out the case is a cheaper option? i have a new trans on it and a new starter and a carb rebuild now so there is a lot of good gear on the engine now, but I'm no mechanic and don't have time or tools to tear a v8 apart.

thx

**bobchris** · 07-11-2006, 11:46 AM

all of that stuff is would go back on the motor, you can not rebuild the bearings you replace them and there are three different bearing groups to replace, crank, connecting rods and the cam bearings. The cam will need to be replaced as well. Then again if you like to half *** things then you do what you want because it's not going to last.

**MiracleDriver** · 07-11-2006, 12:16 PM

I know you can't rebuild bearings, I'm not an idiot and if I were to do it I would do it all. I don't half *** things, that's why I'm here asking questions. I'm trying to get to the bottom of this boat, and its drinving me nuts. I want to know the right way to go about this if it turns out I need a rebuild soon so 1. I don't get raped on price and 2. I don't get something I don't nee. how much should I expect to pay for this kind of work, including parts? How long would it take a qualified mech to do it?

I've rebuilt 2cyl 2strokes before, but never replaced engine bearings. Not quite the same thing considering I can lift out my 2cyl motor with my 2 hands.

**ag4ever** · 07-11-2006, 01:02 PM

Why would you need to replace the cam-shaft? Those things should last as long as the crank. Now, the cam bearings should be replaced, and the lifters need to be replace in the same hole they were removed from, but there is no good reason to throw out a good cam and lifters. If the engine did let go, and they were hydraulic lifters, I would consider replacing them, but they should work fine with a used cam.

**TRBenj** · 07-11-2006, 01:36 PM

Miracledriver, dont take offense from bobchris- he means well and his advice is usually right on. If youre also posting on CCFan under Kylecraft, he goes by 79nautique over there. If thats not you, youre not the only Canadian with a '90 Nautique with oil pressure problems running Quaker State 10w30 synthetic!

You can get a rebuilt short block for $1500-2000. Having your motor rebuilt would cost about the same. Just be sure to get the same rotation as your current motor if you buy the shortblock. If you have the 1.23:1 tranny (most likely), you have a standard rotation motor. If you have the 1:1, then you have a reverse rotation motor.

**bobchris** · 07-11-2006, 02:01 PM

I was just using the terms you used, You need to replace the cam because if the bearing's are shot on the crank then they are going to be shot on the cam and if the bearings are shot then the journels(sp) are shot. SOOOO you have to replace the crank or have the journals turned and use .010-.020 undersized bears for the crank and a new cam because you cannot turn the journals on the cam because all of the case hardening is gone. Then again some people are just cheap and would rather do the job twice to save a little money the first time instead of doing the job correctly the first time.

**MiracleDriver** · 07-11-2006, 02:44 PM

there must be 2 of us in canada with low oil pressure 1990s having carb problems then... :shock:

what a coincidence :lol:

Thought I'd post here to see what others thought. I appreciate the help big time, I'm not a mechanic as stated, but also not an idiot... I understand how motors work, and the basics behind a small block ford, but I wouldn't pay myself to do the work on it... I like to know what I'm dealing with as there are not a lot of great mechanics that know these marine engines around me like there may be south of the border.

I was ripped off and treated horribly by the only correct craft dealer in Ontario so I have little alternative but to take it elsewhere. they know less at the dealer than my small engine mechanic does that's for sure. Although the basics are the same on all v8s I guess.

I'm guessing the long block comes with pistons and cylinders and the short block just the bottom end, I provide all the running equipment including the pan and all the tin.

**TRBenj** · 07-11-2006, 03:14 PM

No kidding. Check out this thread and maybe some of your problems are the same: CCFan post

Good luck!

**MiracleDriver** · 07-11-2006, 04:56 PM

guess my scarcasm didn't come through in my last post... I am the same guy on CCfan.com. Yellow_Flash_Colorz:

sent you an email. I don't want to sell it yet, but we'll see. I want to find out how the carb rebuild goes and change the sythetic oil out with some heavier stuff.

will post the results and look for more input if needed. Thank you everyone for your help thus far. We'll get to the bottom of this incorrect craft :twisted:

low oil pressure 1990 351

low oil pressure 1990 351

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