Westerbeke Generator

dino

dino

Member
Feb 21, 2009
123
Boston MA
Boat Info
2002 380 Searay Sundancer
Engines
8.1s V-Drives
So my 7.0 Westerbeke generator was running extremely rough so we did a compression test
Came up with 210 210 and 209 readings with all plugs removed. Then did another test with plugs in came up with 180 180 90 added oil to the low cylinder an came right up to 250 so assuming bad rings ..
Not sure why plugs being in or out make a difference? Anyhow the question is with a 20 plus year old genny only 450 hours do I pull the genny and rebuild, or look for new? Starboard engine is going to need to come out unless I can disassemble mostly in boat and sneak by but to reinstall will need to come out for sure.I do know the cost of the new Westerbeke gas gennys are insane
 
I would rerun those compression tests. With the plugs in the RPM would be reduced a bit, which will lower the readings.

I wonder if that 90 was an accurate reading at all.

What did the plugs look like when you pulled them? Have you ruled out other problems like a dirty carb causing the rough running?

450 hours on a genset is "nothing", especially if it's an 1800RPM unit.
 
Agreed, bad gas, water in the gas (check the separator), dirty carb, etc. Sounds like a fuel issue to me.
 
I never quite get why the first reaction is a mechanical failure. Your would think, spark plugs, wires, distributor cap, fuel delivery, fuel quality would be have to be checked off before you got to rebuilding the engine.

Most of the 20 year old gas Westerbekes I see still have their original distributor cap, coil and wires. I would rerun the compression check for piece of mind then do a complete tune up on the engine.
 
So had a mechanic look at it few weeks ago and compression came back low on one cylinder on a warmed/hot motor, Very rough starting then when warmed up ran better until a load was put on it and bogged way down putting out like 90volts.
Starboard engine running fine from same fuel tank with valve tech fuel that is treated and used often. New Plugs looked ok maybe slight build up of carbon, new fuel/water Seperator, Carb could very well need a rebuild but all does not explain low compression
even cold should the readings be that far off?
 
One set of readings is off from the other. With or without plugs compression is relative. I like doing warm engines with the plugs out because it is far less stress on the starter and gets to the results quicker.

Before you go down the rabbit hole of a bad set of rings. Check it again.

Could it be a ring problem (or piston problem) .....sure. If the cylinder got water in it and it sat for a while.....that would cause a compression problem.

If the cylinder tests low again.......have your mechanic use a borescope in the spark plug hole to inspect the cylinder walls.

Some history on the generator would be helpful....did it just start doing this or has it had problems before.
 
dino said:
So my 7.0 Westerbeke generator was running extremely rough so we did a compression test
Came up with 210 210 and 209 readings with all plugs removed. Then did another test with plugs in came up with 180 180 90 added oil to the low cylinder an came right up to 250 so assuming bad rings ..
Not sure why plugs being in or out make a difference? Anyhow the question is with a 20 plus year old genny only 450 hours do I pull the genny and rebuild, or look for new? Starboard engine is going to need to come out unless I can disassemble mostly in boat and sneak by but to reinstall will need to come out for sure.I do know the cost of the new Westerbeke gas gennys are insane
Click to expand...
I believe you still have some investigating to do on the compression.

but I wanted to let you know, @Mig22

was able to take manifolds off to slip the genny out and back in….
 
Thanks all for the replies..Generator was running a bit rough this past summer and at one point was only producing 80-90 volts Thats when a genny mechanic looked at it and did a bunch of diagnostics both front end and back end and found capacitors to be bad. It sat for about 3 weeks during this process and when he came back found genny running rough with what he called excessive blow by thats when he did compression test and said that one cylinder was coming up low. I need to find the number but it was much lower than the other two. Someone suggested a leak down test but it just got too late and needed to winterize
 
dino said:
Thanks all for the replies..Generator was running a bit rough this past summer and at one point was only producing 80-90 volts Thats when a genny mechanic looked at it and did a bunch of diagnostics both front end and back end and found capacitors to be bad. It sat for about 3 weeks during this process and when he came back found genny running rough with what he called excessive blow by thats when he did compression test and said that one cylinder was coming up low. I need to find the number but it was much lower than the other two. Someone suggested a leak down test but it just got too late and needed to winterize
Click to expand...


We are trying to help but every story that begins with a compression test is bound to have more issues to understand. What you provided helps but essentially means your mechanic did not identify and solve the right problem. If it was only producing 80-90 volts before he touched it and it did no better after his "bunch of" diagnostics and capacitor replacements........he didn't really solve the problem.....did he? It is hard to trust anything else the guy says even if it may be correct.

The issue that you may have is a rough running engine which developed a problem before he touched it. A rough running generator engine will not hold its proper rpm and fall off AC production. I believe your generator has a mechanical governor and if something is off with the engine.....it will not hold engine speed.

As to what is wrong......even though it is winterized.....a new compression test can be done as well as a cylinder inspection with a borescope. It is maybe an hour of work and would allow you to plan if the generator needs to be removed from the boat which is a lot of work.

Without a compression test and cylinder inspection we are all still guessing. All that said......if the cylinder wall is obviously scarred and will not build compression .....you are in for a rebuild but that is an very unusual event for a 450 hour Westerbeke. If the cylinder wall is not scarred that may suggest a couple more things to try before pulling the generator.
 
Play Date.....You are 100% correct and thanks for the great advice. Will get a cylinder inspection done and do a redo on the compression test and hope for the best
Thanks!!
 
Very little is known by doing a "compression test". More importantly I question a mechanic's credentials who only does this test. A Leak Down Test needs to be done for each cylinder to determine if a cylinder is leaking more than another. This test determines and isolates if there are issues with piston rings, valves, cracks, or head gasket. It is a standard test that all qualified mechanics do.
Here is another tidbit - piston rings do not all of a sudden cause an engine to run rough; they degrade slowly over run time. Valves essentially are the same they will degrade over time unless something externally damaged them.
It seems to me you might have discovered a tired engine but the rough running is due to other conditions; possibly amplified by the tired engine.
 
Highly unusual any piston or cylinder issues at 400hrs on these motors, unless there’s been some event such as overheat, hydro lock…. After the usual ignition maintenance pugs, wires, distributor I would start with checking both the mechanical Governor Oil level/adjustment and the engine valve adjustment’s definitely suspect with those compression numbers. Here’s a link to the service manual - start at page 26
https://www.westerbeke.com/operator's manual/44200_4.5bcgb_7.0bcgb_oper_man.pdf

Items to check related to Engine hunting:
1. Low battery voltage.
2. Generator is overloaded.
3. distributor cap.
4. Faulty high tension wires.
5. Faulty fuel pump.
6. High exhaust back-pressure.
7. Valves are out of adjustment
8. Governor is out of adjustment
9. Dirty fuel filters.
10. Throttlelinkageisbinding.
 
dino said:
So my 7.0 Westerbeke generator was running extremely rough so we did a compression test
Came up with 210 210 and 209 readings with all plugs removed. Then did another test with plugs in came up with 180 180 90 added oil to the low cylinder an came right up to 250 so assuming bad rings ..
Not sure why plugs being in or out make a difference? Anyhow the question is with a 20 plus year old genny only 450 hours do I pull the genny and rebuild, or look for new? Starboard engine is going to need to come out unless I can disassemble mostly in boat and sneak by but to reinstall will need to come out for sure.I do know the cost of the new Westerbeke gas gennys are insane
Click to expand...

Plugs in or out doesn't change anything for the most part, but adding the oil does. That is an old school test of the rings/walls being bad or not. The mechanic put oil in the cylinders to see if the valves or rings are bad. A leak down test would have been better but, that cylinder wouldn't produce much anyway. And to be honest a cylinder showing 90 when cold should then be done again when hot. You can use an inspection scope to see what the cylinder walls look like, but it sounds like to me that the engine may need to be rebuilt.

But before any of that, do a hot compression test. As mentioned the running rough can be other things and if the compression is up near 200 or so when hot.
 
I’ve been reading and following this post. Play and TT know much more about the engine and the things internally possible wrong. Towards the end on the post you’ve said the engine was hunting. Hunting leads me to the governor, could be as simple as oil. Could be linkage or just need adjusting.

Id like to add this. Today I started mine to warm her up for winterizing and fog.
Mine started to hunt right off the bat (when she is cold it does this) you can watch the linkage to the governor as it controls the engine carb. I took my finger and just stabilized the linkage and she ran like a top. When you start yours see if that linkage is taking control

One other story, before I took possession my Westerbeke was giving the dealer the fits. He spent many bucks trying to make it right. Even called in a Westerbeke certified mechanic from VA Beach to drive to Richmond VA. Nothing, no one could fix it. I went ahead and took possession thinking I’d replace it. I was in my slip one week when my neighbor and I got to talking. I told him about the issue, he had it fixed in about 10 minutes, it cost me 2.5oz of 30W oil. The governor needed oil and that’s all it was.
 
Thanks all! Genny never overheated or hydro locked so Im good there. Appreciate all the help...
 
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