Low power, slow to get in plane. Intermittent backfire

Rick2752 · **Posted:** Tue Aug 26, 2014 5:29 am

Just a little piece of info. I went to Autozone looking for a fuel pressure gauge, they had a small kit that was kinda cheap looking. They offered to rent me one. HMMMM how much? 160 dollars, are you crazy???? You get to keep it for up to 90 days and when you bring it back, you get a full refund. So .....FREE right up my alley and its a really nice kit.

Here is the base of the distributor and the inside contacts.

Untitled by rick2752, on Flickr

Untitled by rick2752, on Flickr

Like I said I cant believe it ran

Rick2752 · **Posted:** Sun Sep 07, 2014 9:02 am

Ok finally got around to working on it. I replaced distributor cap and rotor. Hooked up fuel pressure guage and had 30 on high side at idle and around 12 on the low side at idle. I think those numbers are ok. I have spark on every plug wire. Haven't pulled all the plugs yet, to check them that is next. Ay ideas, I don't want to mess with the timing yet until I check all the other pieces. I rerouted all the plug wires and cleaned up their installation. I did find that it is about a quart low on oil, but wouldn't think it would backfire if it was going into limp mode. I am almost at the end of my season so, I'm just going to change the oil. Any other ideas to throw at it?

jayjay4735 · **Posted:** Sun Sep 07, 2014 10:23 am

The only other thing you might want to try is having your fuel injectors serviced. I have the same engine as you and was having similar problems. My distributor cap was also looking pretty bad so had that changed and had the injectors serviced and it ran much better this season. There are only two injectors in that engine so it shouldn't be too expensive to have done. Interestingly with mine the injectors themselves weren't really the problem (the shop told me one was operating at 100% and one at 97%, however when they took them off to service there are filters on them that were pretty dirty and clogged up and that was more likely a culprit than the actual injector.

7cstevan · **Joined:** Sun May 12, 2013 7:20 am **Posts:** 34

Hate to tell you this, but I had the same problem on my port motor just after I bought my 2001 328 Vista last year

I have the GSI 5.7L FI 280 hp motor(s) you have--just 2 of them instead of 1.

Do a compression check.

Turned out to be bad "tuliped" or warped intake valves on the starboard bank of my port motor.

The motor would pop back IE, backfire.

First indications of trouble were the motor shook a bit more than "normal" even though it's bolted in of course
Then, an occasional backfire every 100 yards or so when up on plane--after about 1 mile of no wake zone.
This went on for about 3 trips out--each time it got a little worse and each time I came back.
The last time out it got really bad.
Had the compression checked--zero compression in one cylinder and 50lb in another.
$1700 for a new cylinder head (parts and labor) and it's been great for 100 hours now.

DON'T know how (actually I do, but it seems impossible) but the yard got the FI and intake manifold off AND removed the cylinder head WITHOUT taking the motor out.

Come to find out, that manifold had sprung gasket leaks under the prior owner, so that likely had something to do with it.

Rick2752 · **Posted:** Mon Sep 08, 2014 11:24 am

Man I hope not. If I have to pull the heads on this motor I am gonna change the name of the boat. It's "earned it". Right now. I'm tired of earning it

rpengr · **Posted:** Mon Sep 08, 2014 12:27 pm

On the other hand, have you tried it since the new distributor cap? Old one was pretty bad, so hopefully that was it.

Tuliped Intake valves are a possibility. Usually caused by being "over-propped" (too much pitch), especially on cruisers using high power at low rpm. If a cruiser does a lot of "plowing" for extended periods (not quite up on a plane), that could be a cause.

But let's hope it was just the ignition issues.

Rick2752 · **Posted:** Mon Sep 08, 2014 1:16 pm

I'll try to compression check an check the plugs tonight and report out tomorrow. I have run it since the distributor cap change and it was no better, but haven't run it since I drained the gas. I coin a manual somewhere online that said not to run the 93 leaded with addictive and that it what they had at the marina I think. I also gonna check the filters on the injectors if I can get them out easily. I will keep everyone updated.

jayjay4735 · **Posted:** Mon Sep 08, 2014 3:04 pm

Also I see that you cleaned up the installation on the plug wires, but were able to rule out that the wires themselves are shot? One thing to look for (from what I remember, anyway) is to run the engine at night in the dark, and if there are any cracks in the insulation you'll see little sparks coming out of the wires.

LouC · **Posted:** Mon Sep 08, 2014 3:48 pm

Try to get the engine well warmed up and open the throttle all the way for your comp test, that will make it more accurate.
Backfire can be due to a lean condition as well, what do the plugs look like, is there any air leak around the gasket for the throttle body, any intake manifold leaks? If you have any plugs that are blistered white, that could be a sign of a lean condition. The valve tulip issue is why I like to see engines propped to reach their max rpm as specified. That is something that dealers and mechanics often don't check, and most people cruise at 3500-4000 rpm so as long as the engine will pull that rpm, all seems OK.
Hopefully you will find a more innocuous cause like a clogged injector screen (there's your lean condition cause)....

rpengr · **Posted:** Tue Sep 09, 2014 7:33 am

jayjay4735 wrote:

Also I see that you cleaned up the installation on the plug wires, but were able to rule out that the wires themselves are shot? One thing to look for (from what I remember, anyway) is to run the engine at night in the dark, and if there are any cracks in the insulation you'll see little sparks coming out of the wires.

Another trick for testing plug wires I learned from a mechanic (and saw it work) was this:

With the engine running (running rough), spray the wires with water with a little bit of soap in it. If the roughness goes away, the wires are bad.

I would guess that this works because the water would go into any cracks or pits, and insulates better than air.

Rick2752 · **Posted:** Wed Sep 10, 2014 10:33 am

Didn't get time to work on it but started pulling plug wires while it was running and one of them shocked me. Redneck plug tester. Lol. Plug wires are on order. I still gonna check compression though and change the plugs.

Rick2752 · **Posted:** Sat Sep 13, 2014 11:30 am

Checked compression this morning. Front to back on the right side. 120, 130, 50. That's where I quit. So tired of throwing money at this boat.

jayjay4735 · **Posted:** Sat Sep 13, 2014 11:50 am

That really sucks man, sorry to hear that.

LouC · **Posted:** Sat Sep 13, 2014 12:51 pm

Rick sorry to hear of your trouble, I think the root of it, is in one of your older posts....when you changed the manifolds...I thought I saw rust in the exhaust port...which can happen when that joint leaks between the manifold and the riser. You said the boat was in salt water and if it was in salt the whole time before you got it, then they were past replacement time for sure if they were the originals. Here in salt we don't usually go more than 5-7 years on a set. Unless you have full closed cooling, or stainless manifolds from Hi Tek marine in Australia its just the way it is in salt water. Look at the pix, you can see rust in the exhaust ports in the cylinder head and I bet you have a sticky valve or two that has rust on the valve stem. If its not too bad you can get the heads done over the winter. Your post:

viewtopic.php?f=6&t=12833&hilit=manifolds&start=0

In your flickr pix you have a pic of the engine with the risers still installed. The one on the right hand side of the engine as you face it (port side of the boat) has rust stains on the outside. Often when you see that on the outside, its leaking on the inside.

I also enlarged the photo of the engine with the same riser taken off the port side manifold, its a bit blurry but I thought I saw rust in the exhaust passage. All that should be there is carbon if you have rust then water has been getting into a cylinder. Not enough to hydrolock, but enough to rust exhaust valve stems especially.

Here's my engine during the last manifold change in 2011...you can see into the exhaust ports and there is no rust only carbon...this engine has been in salt water every season, moored in it 6 months out of the year since 2002, it was trailered in salt before that and before that it came from the Midwest.

https://www.dropbox.com/s/u3w9g3qvuxycb ... 1.jpg?dl=0

Here's what the second set of one piece OMC manifold/risers looked like after 5.5 years of use, see how on one side one of the 4 water passages is clogged up. I could have used these again by rodding out the opening, but I put a new set on instead...

https://www.dropbox.com/s/co8mqd4vi8qze ... w.jpg?dl=0

Now these are NLA, so I have to do something different the next time I replace (about 2-3 years). I am thinking of going with the Hi Tek stainless manifolds, because by then I may repower with a new crate engine and I have never liked the old style Merc/Volvo riser gasket design, there is not that much sealing surface, its easy for salt water to corrode the cast iron there and then you get leaks. Merc's dry joint system is an improvement because the water passage and the exhaust gas passage is much more separated. But they use a different outlet diameter size and that would require a lot of adapting to make it work on an OMC/Volvo engine.

So far my engine has had 3 sets of these manifolds on it and never had water in a cylinder ever. I wish I could still get them. To me the standard inboard manifold/riser gasket design is just a very bad compromise. Failure prone in salt water.

People often ask me why I keep my old boat and don't get a 'newer' one. Well around here unless is like 3 years old or less, there is not much point unless it has full closed cooling or a merc with the newer style manifolds. I'd rather start again with the old boat and a new engine set up exactly how I want it (closed cooling, stainless manifolds) than start with someone else's problems.....

So OK after you relax, work it through....do another comp test....this time put a bit of oil in the cyls that are low to make sure its the valves, or do a leak down test better yet that will tell you exactly what it is. I had that same feeling when I was winterizing the boat in 2005, went to pull out the rear seat....and my foot nearly went through the floor.....that lead to....a...BIG JOB....personally I'd rather pull a set of heads anyday....than do that again.....

https://www.dropbox.com/s/e316zo94sig9y ... r.jpg?dl=0

https://www.dropbox.com/s/v24fgzc4yvwm6 ... W.jpg?dl=0

https://www.dropbox.com/s/pes4wf5zt63mx ... n.jpg?dl=0

https://www.dropbox.com/s/g1rnp0kl1gqpz ... g.jpg?dl=0

rpengr · **Posted:** Sat Sep 13, 2014 6:11 pm

Rick2752 wrote:

Checked compression this morning. Front to back on the right side. 120, 130, 50. That's where I quit. So tired of throwing money at this boat.

Yes, It sucks, but not the end of the world. You just need to pull it apart down to the heads and have the heads rebuilt. Do not even need to remove the engine, and you already have new manifolds.

If you have any desire for a little more horsepower, now would be the time change out the cam.

www.iFourWinns.com

Low power, slow to get in plane. Intermittent backfire

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