2004 5.7 gi misfire cylinder #5

[CAPTKEV85]

Hey Everyone, Last week I had posted that I'm possibly purchasing a 1989 carver santego 30 with fresh water cooled 5.7 gi volvo penta dps. Its an older friend of mine that is selling the boat to me so today I went through the motors to make sure they run. The hour meter says 993hrs. These motors you can eat off of them that's how well maintained they are or maybe not. So since they have been winterized by a marina, today I fired them up since sitting all year. The marina mechanic asked told me "you know they are winterized". I said ok I'm not buying a boat with out running them and a sea trial. . I noticed right away that the port motor had a skip while cranking. It caught my attention but I thought maybe the fogging oil fouled the plugs. These motors are fuel injected. I Increased the throttle to try and clear it out. when I brought it back to idle it stalled. restarted it and noticed at idle the motor seems low in rpms with a little shake to it. So I started the starboard motor and kicked right over with no issues at all and it idles around 600rpms.

Now I decided to pull the plugs to check condition and #5 seemed wet. I put a new plug in and and tried it again. Still Misfire. Now with the motor running around 2000 rpms one at a time I pulled the plug wires off and reconnected them. #5 did not change at all when I pulled the wire. Spark was traveling from the cap to wire as I was connecting it. So now I'm getting concerned. I took the #5 plug wire from the starboard motor and tried it on the port. Still no change. Also the injector is clicking so I'm assuming its working.

So now I'm thinking a possible compression issue. Tomorrow I'm going to start the motor again get some heat in it and do a compression test on that cylinder. Does any one know the compression specs on this motor? and is there anything else I should look at or diagnos? thanks.

Also I noticed a possible gimbal bearing noise on starboard motor when turn the drive or trim up or down. Is it the same procedure like a Mercuiser gimbal?

thanks again everyone.

 

[QBhoy]

I’d think about 140-160 would be healthy ball park...but before all that...I’d take it for a good run and get it up to operating conditions with P&T’s. It’s then you get the full feel of the health of engines.

 

[alldodge]

New motor would be around 150 psi

#5 is wet and plug is sparking, that is a puzzler, even if it was flooding on that cylinder it should be burning. Maybe just a plug wire. Could swap one

Gimbal bearing noise will be the same as Merc

 

[Scott Danforth]

are the motors original? if so, 89 VP's drives would have been AQ series 290-A DP's if originally equipped with VP's. there is no gimbal bearing in an AQ series. they would have a PDS (Primary Drive Shaft) in the flywheel housing that would need the drive and motor pulled to replace.

The motors would have been AQ-271D's for 1989, or possibly 570's depending on month of manufacture as there was new nomenclature for the motors starting in 89. however they both would be 5.7's with holley 715CFM carbs and a prestolite distributor

if you have 5.7 GI motors your motor was converted over at some point to a newer motor

or was the boat originally a mercruiser drive and converted over and using later VP drives and motors?

if the VP motors are still running the original prestolite distributor from 1989, look at the cap and rotor, any amount of corrosion, change them. it was common for the cap and rotor to get just enough corrosion to either fire two cylinders at the same time, or to have one not fire. when that happens, you feel it. then if you buy the boat pull those prestolites out and replace with Mallory, or other

post a picture of the motor and the drive so we can see what you have.

 

[CAPTKEV85]

The boat originally had mercruisers and drives. In 2004 the owner had the entire drivetrain replaced with 5.7 gi and vovlo Penta duo props manufactured that year (2004). He had spent a lot of money on this conversion. His reasoning was he had owned merceuiser for 30 years and always had something going on. These Volvo’s never gave an issue till now. The engine blocks are painted red and fresh water cooled. So this morning I put a new cap and rotor on the motor and still no change.

So I did a compression test cylinder 5 had 10psi and cylinder 3 has 110 psi. All other cylinders are around 160 psi.

Something is obviously going on in those two cylinders note that the motor is quite and I do not here any valve train noise. So my guess is possibly rings or head gasket?

He is a friend of the family for a long time so I wouldn’t think he would sell to a friend knowing it has an issue.

 

[Scott Danforth]

Do a compression test. Also, VP HX cooled engines are only half systems. If the boat is a salt water boat, the manifold may be past its time and leaking water into the cylinders. Cylinder 5 and 6 would usually be first effected.

your 2004 vintage drives will have gimbal beatings

 

[CAPTKEV85]

I did the compression test. It’s listed in previous post. So if Volvo’s are half fwc am I correct to say that manifolds and riser are salt water? I never even thought to check. Once I saw the antifreeze and heat exchangers I was like nice fwc engines.

 

[Scott Danforth]

Missed the compression numbers. Do a leakdown test, and pull the exhaust manifolds. I bet you find rusty valves. Easily fixed with a valve job

 

[QBhoy]

Ok. So maybe I’m stating the obvious here...but from memory...cylinder 3 and 5 are next door to each other. Both low on compression would suggest that there is a loss of compression that’s common to both. Even between both. Look towards the cylinder head or otherwise both 3 and 5 have been previously affected by the ingress of water on that side, via the usual manifold issues. Since then, valves have become compromised and causing this.
Finally, there is the old total failure and frost damage nearby

 

[Lou C]

Well the only way to differentiate HG problem from stuck exhaust valves is to pull the manifolds and look. If the valves have no corrosion then you have to go further. You can in the interest of time drain the manifold (make sure to pick up a few spare VP manifold to elbow gaskets) and remove the elbow on that side. If water has been leaking in it will be obvious; rust trails inside. Any water or antifreeze present on the plugs when removed? Water suggests leaky elbow gasket antifreeze suggests head gasket. VP had problems with the gaskets on this style of exhaust and they were revised a few times. To do s valve job on these engines is not that bad of a job if you’re a competent backyards mechanic....
the 10 psi suggests a valve not seating....
if those engines were installed new in 04 and run in salt continuously then the exhaust should have been changed at least twice by now (figure every 7 years or sooner if you see rust trails on the outside of the manifold to elbow joint) ......
i have done this on our boat and never had water in a cyl from bad exhaust. 2 sets of OMC batwings (changed in 04, & ‘11) and the last set I converted to the center riser style in ‘17 when I did a top end overhaul.
so if that was not done that could be the cause....
if you find that to be the case figure on checking the other engine too!