Engine noise
 

I just picked up a 1988 Formula 206 and it has the 320HP MPI small block in it.I bought the boat knowing it had a knock,but I can't pin point what it could be.It starts and idles fine,a little rough, ans revs to 2000 rps with no problem.Over 2000 rpms it develops a knock sound but not as loud as a rod knock.It has 70 psi oil pressure and if I rev it up fast there is no noise at all,weird.I pulled the drive off to make sure it was not a bearing or something.I pulled a valve cover off and no loose rockers,motor only has 87 hours on it.Any ideas before I pull motor tomorrow???


Thanks Nordic95

Re: Engine noise
 

sounds like a rod bearing.

Re: Engine noise
 

Wouldnt that lower oil pressure??


Thanks Nordic95

Re: Engine noise
 

Hello,
just went through crap like that. You might consider taking off your oil filter, check the inlet brim or cut it open to see if you can see those little sparkles or a hint of metal dust in your oil. Some times you can pull the dip stick out a see sparkles in the sun light. My oil pressure was pretty good but I didn't let it run very long to get really warm either.

Re: Engine noise
 

Is there any place like Summit Racing for car parts but for boats parts? Like with Summit you could order a complete rebuild kits with all gaskets and bearings for a specific engine.I would like to find a place for marine engines except the normal places that you have to order individual pieces.


Nordic95

Re: Engine noise
 

All the gaskets marine to auto are the same, except the head gaskets. and the last time I bought head gaskets for a big block, the fel pro marine and street were the same.

I had teh same issue that you have years ago on a SB, and it too was teh rod bearings. didn't affect oil pressure at all.

Re: Engine noise
 

I think the closest thing to Summit for marine parts is CP Performance.

Have you done a cylinder kill test to try to link the knock to a specific cylinder?

Cutting the oil filter open to check for metal is not a bad idea, but what about having an oil analysis done? That would tell you what type(s) of metal you have in the oil and help you determine what might be causing the knock.

Dave

Re: Engine noise
 

I'd do a compression test, a small block marine motor I looked at last year had a strange intermittent knock, it was a head gasket blown from a overheat.

Other thing I have seen is when they have the crank mounted raw water pump. (Volvo type) the rubber bushing was gone from the stay bracket and it made a horrible knock at low rpm's.

Re: Engine noise
 

I may be going out on a limb here - just going from what I;ve heard - but I think rod / rod bearings issues aren't uncommon in these motors. Still have to find out what your real issue is of course.

Re: Engine noise
 

Could be a wrist pin

Re: Engine noise
 

Would the wrist pin gouge the piston bore?I'm thinking the motor sat for years,maybe stainless pin adheared to piston then when started it gouged it up.Would the wrist pin noise go away at idle and up to 2000 rpms?I'm ripping it apart tomorrow and we shall see what happened.


Thanks Nordic95

Re: Engine noise
 

Let us know what you find :drink:

Re: Engine noise
 

Pulled the motor out today and found and issue with the block.It has two 6" long cracks,one on each side if the block right by the head.I see rust and water running down the block.So as I figured I will need a long block.Who carries replacement long blocks that has a good reputation,any one here on the board?

Nordic95

Re: Engine noise
 

1200 BUCKS ISN'T BAD
http://www.rapidomarine.com/default....s/default.aspx

Re: Engine noise
 

Any body ever use these guys???

Nordic95

Re: Engine noise
 

Pulled the motor yesterday and I think I found a problem.Looks like someone forgot to drain the block last winter.Time to order a long block,its probably not worth looing for just a block and switching everthing over,or could it be?Tell me what you think.




Nordic95

Re: Engine noise
 

My friend just bought a 351w reverse rotation from them,spun a bearing. Only 1 hour on engine. They are paying to p/u engine and say they will send out new one after inspection. Hopefully they keep their word. Owner seems to be a good guy. Don't know if they will re-inburse for labor. I will keep you posted.

Re: Engine noise
 

Yes please do,they are the cheapest I found so far,but I also remember that I get what I pay for.

Nordic95

Re: Engine noise
 

We needed the engine fast,they built the engine and shipped it the same day. This may have something to do with the bearing issues.

Re: Engine noise
 

Same here,I would like to have it by this Fri. I'm still shopping around.


Nordic95

Re: Engine noise
 

Odds are that you get get a long block or a low hour take out for near the cost/time/labor that you will have in taking apart and putting back together the one that you have. You are just looking for a standard SB chevy, not any exotic high performance BB.

Re: Engine noise
 

Only looking for stock power,I'm thinking the same thing,I'm finding rebuilts for 1500 to 2500.Not worth messing with old motor,except old motor only had 87 hours,female use on it.Hate to throw it away.

Nordic95

Re: Engine noise
 

JB Weld/Marine Tec the crack :drink:

Yea, that the problem. A simple no winterize, and a bunch of good parts sit there and are worth very little. Got any junk yards around that have any blocks for a couple hundred? Or just take the motor apart, and keep the internals in case anything on the rebuild every breaks. rods/heads/pistons/oil pump etc

Re: Engine noise
 

I have seen pressed in pins make noise with change in load. Dont look like that was your problem though :eek:

Re: Engine noise
 

Keep it as a chandelier :cool:

Re: Engine noise
 

You cannot go wrong with the GM crate 350. All new parts and basically ready to drop in. Snatch the heads and add Felpro stainless head gaskets and you're set. Add a cam and you'll make a little more power. I think the cost is less that $1500 from Summit.

Re: Engine noise
 

I took the engine to a local shop that does marine engines.$1800.00 for them to take old engine apart,mic all pieces,all new bearings and pistons with rings,assemble complete engine with marine gaskets in one of there blocks including all machine work with 1 year unlimited hour warranty.Their shop is only 30 minutes from me and I couldnt beat the deal,lets see how it works out.Best part is I droped it off today and will have it back on Fri.

Nordic95

Re: Engine noise
 

dont you already have alot of leftover used parts from your last two rebuilds that you can use ??

Re: Engine noise
 

NOPE,this project is a small block,other project is BIG BLOCK.I just cant get the parts to bolt on. :D