5.7 Mercruiser Problems

WateryGrave

Recruit
Joined
Sep 22, 2004
Messages
3
Hello! I have recently purchased a '87 19 foot renken speedboat with the 260 horse mercruiser and alpha 1 outdrive. The other day I was out on the lake cruising at 4900-5200 rpm for a few minutes when the boat lost power, started detonating, overheated, and lost oil pressure, all in this order. After coming to a stop, I noticed that I had a oil film in the water coming out of the exhaust. After letting the boat cool down from near 240*F temps, oil pressure climbed back to normal, and I nursed it home. I did not see any evidence of water in the oil, either. I think I may have a popped head gasket, but I am unsure at this moment. What's everyones thoughts on my dilemma?<br /><br />Thanks,<br />Zach
 

Chris611

Petty Officer 2nd Class
Joined
Jun 10, 2004
Messages
100
Re: 5.7 Mercruiser Problems

I'm not an expert on the engine part, but I think that your WOT is a little high. I think it should be between 4200 - 4600 RPM. I know it isn't much help, but at least it will get the post to the top.<br /><br />Chris
 

Trent

Captain
Joined
Nov 17, 2001
Messages
3,333
Re: 5.7 Mercruiser Problems

Pull the plugs and look at them. One that is real clean is getting water on it. If so get some oil down into that cylinder pronto!<br /><br />How do you know it was detonating? You need to check the risers and manifolds for blockage and pressure check for cracks. Id also check the impeller in the outdrive.
 

Hog Wild

Seaman Apprentice
Joined
Aug 29, 2004
Messages
40
Re: 5.7 Mercruiser Problems

I believe your water impeller failed, the engine overheated and died. The over heated oil lost it's viscosity and leaked past the rings and also was so thin that's why you had no oil pressure. A popped head gasket would not over heat a motor, I mean why would it? Only reason and engine would really suddenly over heat is loss of coolant. Loss of coolant would cause all that you mention. Fix the coolant flow and then see how the boat runs, beware other things may have melted like the water shutters, change the engine oil as it's damaged, beware of what the heat damaged?
 

WateryGrave

Recruit
Joined
Sep 22, 2004
Messages
3
Re: 5.7 Mercruiser Problems

Well, I'm planning on pulling the engine next week for a rebuild. I think I'm gonna go with a vortec headed 355 with 9.3-1 comp. Are the shutters located in the lower unit? If so, I will have them inspected with the lower unit. I'm a hot-rodder at heart, so some of this boat mumbo-jumbo is new to me. I appreciate the responses!<br />p.s. Anyone know about boat power steering systems? I have a lot of side to side swing, and the wheel is very stiff. I do not think I am getting any power assist. What do you guys think?
 

Bonus

Seaman Apprentice
Joined
Aug 31, 2004
Messages
30
Re: 5.7 Mercruiser Problems

Where you gettin your engine. I was thinking about a similar engine. <br /><br />Bob in Co
 

tommays

Admiral
Joined
Jul 4, 2004
Messages
6,768
Re: 5.7 Mercruiser Problems

we finished a repower on a 1977 correct craft this year and it was well worth it because we will own the boat forever<br /><br />it was ford powered and not standard rotation so we were luckey to find a new motor that allowed all the old brackets to bolt on<br /><br />thats were the fun starts you should look into the total cost of buying a block VS buying one with manifolds distrubte alternator carb ect<br /><br />we bought everything as we went and it added up because it became apparent it was a bad idea to resue allmost anything from the old motor the parts were as tired as the motor was<br /><br />the other thing you need to think of is that a alpha drive is going to be real near its HP limit with the extra power from the 355 it will take it if your carefull but hard driveing with that much power will kill it<br /><br />tommays
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
71,309
Re: 5.7 Mercruiser Problems

Welcome to the iboats forums Zach.....<br />
I'm a hot-rodder at heart, so some of this boat mumbo-jumbo is new to me.
Well,<br />You might want to find yourself a Manual that covers your Merc. drive,+ engine...... And Read Up........<br />They can be found at the link at the top of this page, or ebay, or wherever.......<br /> boat mumbo-jumbo is the langauge of choice here........ :D <br />We'll All be Glad to Help...... But, it's Alot Easier if we're All talking the Same boat mumbo-jumbo............... ;) <br /><br />Your 1st Issue, Started with the Overheating of the engine,+ got Worse from there......<br />
"I was out on the lake cruising at 4900-5200 rpm for a few minutes"
As mentioned before, you're Really Winding it a Little Tight........ <br />4600/4800rpms is about All that motor Wants.......At WOT(Wide Open Throttle)........<br />"cruising", is more like 3200/3500rpms......<br />
I'm planning on pulling the engine next week for a rebuild.
Doesn't really matter Now.....<br />Your MachineShop of choice will be able to tell you the extent of the Damage Done........<br />
I have a lot of side to side swing, and the wheel is very stiff.
My 1st Guess is that your Gimbel Ring is Worn, That's the side to side Slop you're getting......<br />And,<br />Your Steering Cable/Helm is Probably Binding, causing the Hard Steering........<br /><br />Disconnect the pin at the Tiller-end of the Cable,+ See What's Binding..........
 

WateryGrave

Recruit
Joined
Sep 22, 2004
Messages
3
Re: 5.7 Mercruiser Problems

Thanks a bunch for the advice! I didn't mean to come off like a jerk about the boat 'mumbo-jumbo' comment. I will pick up a manual covering the mercruiser drive and engine this week to research what I'm getting into. As far as the limitations of the Alpha-1, is there another drive that I can swap to without a major amount of work? Thanks for getting me on the right heading, guys!
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: 5.7 Mercruiser Problems

Nope, no other drive will hook up to the Alpha transom shield and pivot housing. Not even the newer Alpha I Gen II's will bolt up to it.
 

98LarsonGM57

Seaman Apprentice
Joined
Oct 11, 2003
Messages
32
Re: 5.7 Mercruiser Problems

On my 5.7 I've noticed that if she is a half quart high on oil and I take her much north of 3800 the oil gets slapped to a nice foam and the oil pressure falls off... p
 

Hog Wild

Seaman Apprentice
Joined
Aug 29, 2004
Messages
40
Re: 5.7 Mercruiser Problems

98LarsonGM57, you need to start your own post not tail off of this one.
 
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