Help me think this through!

David Kane · Post by **David Kane** » Fri Jun 19, 2009 8:20 am

I put a fresh set of spark plugs in & got the timing & dwell set. Only around a 25 RPM swing on the tach needle; much better than the 200 or so swing I was seeing. I figure it was due to fouled plugs missing. Took the boat out for a test ride. Could only get the starboard engine to hold steady RPM's at around 2100-2200 tops. Taking it above that, the RPM's would drop back down.

Afer work today, I'll recheck my compressions on the outboard bank-expect like you said, RWS, that they'll still be low. Will then squirt in some Marvel Mystery Oil & let set overnight.

I did talk to my mechanic, who is an auto guy, yesterday afternoon. He said he's got some time Sat. morning. I'll call him @ 9:30am to get him to come over & do a leak down test. Of course, will run in engine to get to operating temp. 1st.

Dan Faith · Post by **Dan Faith** » Fri Jun 19, 2009 9:13 am

I agree with RWS compression is independent of the electrical problem. If worn rings were the culprit you would see more even low readings on the compression. As stated you need to do a leak test to comfirm what the cylinders will hold. When you had the heads off how bad was the ridge in the cylinders? You also could have a broken ring or sticking rings.
Let us know how you make out on the readings. Buy the way #7 if a leak in the water jacket is where the water will settle and show rust along with #8.

David Kane · Post by **David Kane** » Fri Jun 19, 2009 11:16 am

Suprisingly enough, there were no noticable ridges last year on any engine cylinders, indicating virtually no appreciable wear. Cylinder walls looked in real good shape, but we didn't mic them. Not bad for 33 yr. old engines! Maybe I'll get lucky & the mysytery oil will free up what turns out to be sticking rings. #7 is right where I saw the rust.

RWS- my engines face backwards-have Walther vee drives behind the engnies/transmissions (fwd on the boat) to reverse powertrain direction into the prop shafts. Engines don't have a 'tilt' per say, just that the boat at rest tilts slightly fwd, so water will tend to settle at the back of the engine/exhaust manifolds, at #'s 7 or 8 cyls. I've only seen rust indications by #7. All my problems with the starboard engines seem to be on the outboard bank (#'s 1-3-5-7 cyls). Only about 20 hrs. difference between engines, with more hrs on the starboard one.

David Kane · Post by **David Kane** » Tue Jun 23, 2009 7:51 am

Didn't get to put the Marvel Mystery Oil into the crankcase until Sunday. On Saturday wined & dined my wife's cousin who came up. When I went to pour the oil in the crankcase Friday night, I saw oil/water glop on my fill caps. The water temp. gage on the satarboard engine has been reading low-around 110, but I haven't been trusting the gage. I'm hoping the glop is from a bad thermostat not getting the engine hot enough to burn off the condensation. I did suck out a quart of oil from the crankcase to allow for the quart of mystery oil I was putting in (dipstick read full) & the oil didn't look chocolatly, so maybe I avoided a bullet there. Although I have been running a 160 degree thermostat in it, I went with the standard 142 deg one. Also have a new 106 one if needed. Put in the new thermost Sunday afternoon, mystery oi in the crankcase & sea foam in the gas tanks to hit the problem from both ends. Took the family out for a long cruise Sunday evening. Did get the starboard engine up to 2700 RPM, 500 better than before. Above that, she would backfire & not hold RPM's.

Played 'hooky' yesterday-literally. My daughter's fiancee asked me to go perch fishing, so we took the little boat out. Hadn't done any lake fishing in around 40 years. Bought fishing poles for all the boys and me 2 Christmas's ago this was the 1st time we both used ours. So, didn't do any work on my big boat engine yesterday.

I'm going to check my points again. They haven't been holding gap very well, and athat my be contributing to the lack of RPM's & bckfiring. I think the marina service put in automotive stuff. If the point gap is closing again, I'm going to buy marine sets for both engines & replace. But 1st, will redo my compressions on the outboard bank of cylinders on my starboard engine to see if there's any improvement. If the pressue still is low, then will do the leak down test. If I end up with having to pull the engine, one of my other daughter's finacee is a service guy at a Ford dealership & he said he'd help me pull it.

May not get to to work on my starboard engine until next week. Daughter graduating from nursing school tonight. Will probably work late Wednesday & Thursday to get all my work done this week. Friday morning am involved in a disaster exercise for our county. This weekend is drill weekend for me in Columbus. Busy...busy...busy!

rossjo · Post by **rossjo** » Tue Jun 23, 2009 8:09 am

"Although I have been running a 160 degree thermostat in it, I went with the standard 142 deg one. Also have a new 106 one if needed."

106deg is WAY too cool (didn't even know they made 106deg thermostats). I'm not sure 142 is warm enough either.

Dan Faith · Post by **Dan Faith** » Tue Jun 23, 2009 10:36 am

David,
Backfiring check the distributor cap, with moisture if may be arching accross the contacts. On my 318's I have a gasket to seal the distributor from moisture internally. Also, some of the symtoms could be valves or lifters at 2700 and a broken spring will cause float and backfiring.

By the way are the perch hitting? I'm looking at getting out this year when they start.

Dan

rossjo · Post by **rossjo** » Tue Jun 23, 2009 11:01 am

Yes, a broken spring can rear its head in many ways - including loss of compression, back-firing, etc.

After you do your leak-down test, you should pull the valve covers and check for a broken spring - before you consider an engine rebuild!

David Kane · Post by **David Kane** » Tue Jun 23, 2009 11:45 am

106 was a typo. Should be 160.

Brand new (not rebuilt), heads, springs, lifters last summer. If it is a broken spring, wouldn't it show up at all RPM's?

Dan; I know I don't have a gasket seal for the distributor cap. Will check on that when I contact the merc dealer here. When you say ...seal the distributor from moisture internally..., do you mean some kind of seal between the distributor & the engine?

Caught 16 perch yesterday-wouldn't call that spectacular, but, hey, I haven't gone perch fishing, or any other fishing in Lake Erie, in around 40, yes, 40 years! So, for me, that was great. With lake temps rising, perch catches may be dropping off. I see where the daily limit west of Huron is dropping from 30 to 25 effective 01 July. My wife, Dianne, fryed the fish up last night-they were delicious!!!

Dan Faith · Post by **Dan Faith** » Tue Jun 23, 2009 12:04 pm

David,
Most valves have two springs, in my younger days when racing if one of the two were broken it would run fine a lower RPM's but miss and backfire at the higher RPM's. also a collapsed lifter would do the same thing. The seal I have is between my distributor cap and the distributor base.

I hear the reduced perch count is on the western end of the lake. I hope to get out in the next couple of weeks, I missed the walleye when they were hitting.

David Kane · Post by **David Kane** » Tue Jun 23, 2009 3:12 pm

Thanks for the reply Dan. Will look at the springs/lifters if I can't attribute the problem to ignition. They're defining western Lake Erie as that portion of the lake west of a north-south line from the Huron River.

prowlersfish · Post by **prowlersfish** » Tue Jun 23, 2009 8:33 pm

142 deg thermostat if its raw water cooled

RWS · Post by **RWS** » Tue Jun 23, 2009 8:43 pm

with regard to the backfiring, it would be a good idea to confirm the firing order and the plug wires in the dist cap.

It's a remote possibility however a couple of them may be reversed.

RWS

David Kane · Post by **David Kane** » Wed Jun 24, 2009 8:18 am

Rechecked order when I did compression check. Made up tags with cyl # marked on both ends of spark plug wires when I rebuilt last year. Even have the plastic seperators so they don't get all turned around on each other. All OK.

Jerry · Post by **Jerry** » Wed Jun 24, 2009 10:36 am

My Dad had an old Silverton that would not reach the proper RPM range and also would not hold a steady dwell. It seemed as though every time he took the boat out he had a new max RPM.
It ended up being the distributor itself as the upper bearing was shot leaving too much play in the shaft. We purchased a new distributor rather than rebuild his and it was like having a new engine. I would have thought with the slop that it had, that it would have eaten the cap and rotor but it didn't.

RWS · Post by **RWS** » Wed Jun 24, 2009 12:36 pm

The backfire may or may not not be related to the compression problem, which is a problem within itself.

Have you checked the

1) vacuum spark advance

2) mechanical spark advance

These can be checked with an ADVANCE TIMING LIGHT a timing light which has a dial on it allowing you to determine the amount of TOTAL ADVANCE

This was a problem on one of my 454's which was resolved by freeing up the stuck mechanical advance weights and springs. (Delco system)

The only way I discovered it was with the advance timing light.

I spent a lot of time on those and many other problems. Never was stranded, but came home on one engine a couple of times. Once was due to the failure of an ignition coil.

I really LOVE my old school mechanical diesels. If they will crank and have clean fuel, we can go. no points, spark advance, sticking carb needle valves, jets, floats, plug wires, etc.

Although not the best choice in every application, this thread has really made me think about the blessing those diesels realy are.

RWS