Perkins 4-108 Questions

[Mediator]

Hi all, new boat owner and new to CF so here goes:

My boat has a 1989 Perkins 4-108 with 3,500 hours on it. Lots of info about the engine online but I still have a few unresolved questions:

Idle Speed: the techometer works very intermittently (see below) so I don’t have hard numbers, but when I first bought the boat it idled at around 750 RPM in neutral and almost 500 in gear. The engine rattled like crazy so I made a habit of increasing RPM every time I shifted into gear. I’ve since changed the idle speed, first to 1200 RPM in neutral and then, out of concern for my clutch, back down to 1000 (about 800 RPM in gear). Does this sound about right to you guys? Sometimes in forward gear at idle I’ll get the crazy rattling again, once the alternator kicks on and the RPMs drop.

Gauges: of the four engine instruments (tech, voltage, water temp, and oil pressure) only the least useful one, the voltameter, works with any degree of reliability. The tech works about half the time, and the water temp and oil don’t really work at all. Is it worth buying a new panel, buying individual guages from defender, or looking into the sending units first? I only care about the tech, water temp, and most importantly the oil pressure, because...

Oil consumption: as others have said on this forum, the Perkins 4-108 is “externally lubricated.” We go off the dipstick (about a quart) every 12 hours, with most of it landing outside of the oil tray. It makes a mess, and there have been times on long passages where we had to run the engine for a day and were truely concerned about running out of oil. Most of it is coming from the front and rear seals - how do you replace the rear seal without pulling the engine? It seems like the transmission would be in the way. Also, I have some oil coming from higher up, maybe from the head gasket or valve cover? Is that likely?

Smoke in the exhaust: the engine doesn’t smoke at all except for when it is under very high load (such as full power from standstill when trying to make a congested bridge opening). Then I get a bit of blue smoke. Is this something worth investigating? Like I said, it’s based on load, not RPM.

Thanks a lot for the help, and looking forward to being a part of this community.

[Cheechako]

I can't help with all of it but here goes:
-You may have an alternator driven tachometer, These often will not come on until the alternator is charging. Do you know what type of alternator and regulator you have? Stock or higher power?
-Idle: It sounds like the engine lugs down a bit when you first start it due to the alternator producing a lot of current. So you may need to just run it a bit at higher fuel until the bulk of the charge is done... often 15-20 mins. IIRC my 108 would idle nice at about 850+ rpm. Been years though.
-By engine rattle do you mean just what you hear from the cockpit, or do you mean it's actually lugging down a lot? Often various things around the engine may rattle at low rpm with diesels.
-Gauges: Often it's not the gauges at all, but senders or wiring etc. Any movement at all when you first turn the key on on the dials? You need to get in and diagnose the viability of the wires and the senders. It would be worth you buying Caldwell's good book, Boatowner's Mechanical and Electrical Manual. Info on many of your questions in there. How gauges work etc.
- a quart every 12 hours is a bit much, but I guess it's obvious it's leaking. You need to remove the pan to reseal it. Is there room? usually there isnt. Surprisingly my 4-108 circa 1985 leaked no oil. I was evidently lucky!
-IME there should be little smoke under reasonable load,

I love those passport 40's, nice boat. Maybe worth getting that engine pulled, resealed. Maybe even have the head cleaned and checked and the injectors tuned up.

[Mediator]

Thanks for the advice. I love this boat, just slowly discovering it’s quirks.

“Lugging” is a good way to describe it. There is a very sharp divide, around 800RPM, between when the engine purrs (800+) and when it starts making a huge racket (-800). It is identifiable both by sound in the cockpit and vibration level. Part of the sound is the increased vibration rattling other things in the boat (namely the stove).

I’ve heard about the alternator-driven tachs. However the tachometer doesn’t have an identifiable pattern of when it does and doesn’t work. Sometimes it works on startup, sometimes not. After 12 hours of motoring, sometimes it’s working, sometimes not. It doesn’t seem to correlate to alternator load. The water temp gauge always moves but, unless my engine is really running at 250F, I don’t think it’s accurate. The oil pressure bounces all over the place.

Speaking of alternators, I think it’s a 100amp. However at most I’ve only been able to get 33 amps from it, according to the battery charge monitor. That was with my 400amp battery bank at 50% charge and the engine at 2,000 RPM. I’ll probably post in the electrical section of CF and investigate further.

I don’t think the oil is leaking from the oil pan, it seems to be from the front timing cover and the rear seal where it bolts to the transmission. The rear seal leak appears greater than the front.

[model 10]

Mine was using a qt in 8 hours!
You can change both seals with the engine in place and you don't need to remove the oil pan. The front seal is easy and the vibration damper probably has a groove worn in it. A speedy sleeve or install the seal a little proud of the cover.
The rear is a big deal. Remove the transmission, the starter, the rear engine mounts, the bell housing the damper plate and then the flywheel. The rear seal is in a cover plate over the rear of the crankshaft. It's pretty hard to get the seal to fit into the grooves of the plate but you can do it.

[DougR]

- probably the low RPM noise you hear is damper plate and gear rattle. The 4-108 engines that I have been involved with were equipped with spring damper plates on the flywheel to absorb torsional pulses from the crankshaft and prevent the pulses from feeding into the transmission. At best, spring plates are marginal to begin with, and when they become worn they both rattle themselves and also pass vibrations into the gearbox which you hear as "gear rattle". Raising the RPM slightly smooths out the idle and brings the pulses closer together so they are not as abrupt and noisy. It would probably be a good idea to consider pulling the transmission and replacing the spring plate sometime soon, although if you are aware of the situation you can get by for a long time by avoiding low idle situations.

- You can change the front crankshaft seal easily with the engine in situ if you have decent access to the front of the engine, but before going that route make sure it's the seal that is doing the leaking, and not the timing cover gasket. If it's the gasket, this can also be changed fairly easily with reasonable access and you can do the seal at the same time.

- The rear crankshaft seal is a more complicated affair, as it's a "rope" type seal located in a carrier behind the flywheel. In all likelihood this will require pulling the engine out of the boat.

- As you mention, you might have a valve cover gasket leak, or perhaps the valve tappet cover gasket on the side of the block opposite the injection pump. All you can do is clean everything up and start start looking.

DougR

[hellosailor]

What Cheechako said.
The intermittent tach and gauges all sound like there is bad wiring involved. Time to spend a weekend getting dirty and literally taking apart the electrical system and mkaing sure everything is clean. Clean splices, clean contacts, by now the boat may literally need new wiring in places, not just tightening things up.

The alternator should have an identifying plate or stamp on it. If you don't see one, look harder. You really need to know what that alternator is. If there's absolutely no mark on it...it may be worth taking it to some alternator shops to see if anyone recognizes it. (And don't assume the first guy is right.)

Engine "noise" could be from the valves badly needing adjustment, or from other problems. Could be that the smoke under high load is also a valve blow-by problem. But again, the engine is old enough that it should be worthwhile to find a competent mechanic (that'll take a long while) and have them check it out. Valves, compression, in the main bearings are both leaking oil as well...it may be time to plan ahead for an overhaul or rebuild, before the engine decides in needs one "now". When they are left to make that decision on their own, somehow they always pick the least convenient moment.
Also, the "rubber" engine mounts, that secure the engine in place? Yeah, the folks who make the best ones (Gates, Goodyear, etc.) claim they have a five-year life and then should be replaced. They harden and eventually crack. They're supposed to be flexible.

3500 hours is no issue, the problem is it is going on 40 years, and even if the hour reading is true, that's a long enough time for an engine to go without service.

[rbk]

To ad to the alternator/tach issue you can install field disconnect switch which you can use to turn off your alternator and allow the engine to warm up before applying load. The surging could also be the field energising and de-energising as the charge controller attempts to float charge your full battery bank. The only catch to the above is you loose your tach when turned off but will save your engine, alt and tach and by now you can already tell about what rpm you're running at just by listening. The leaks have been covered above, id also start with the valve cover and check the valve clearances while in there as it may help reduce some of the smoke you're seeing (not the blue smoke though, just watch the cold loads and lay off the throttle when possible and gradually bring her up to speed) then the front seal then the back. It should be noted that removing the engine doesn't necessarily mean out of the boat, just out of the engine compartment; lots of cardboard, tape and plastic and do it in your cabin with a rope, cumalongs and pulley's.

[Almost-There]

There's been some great advice so far,all I'd add is to check your motor mounts. Chances are they're worn out and with the boats age I'd most likely just replace them.

As far as the oil leaks go. I'd clean the engine as good as possible with Brakleen etc and add a dye kit to the oil.this will identity the leaks. But to be honest I'd just go ahead and change the front cover gasket and seal along with the valve cover gasket and go from there. While you're in there I'd have the injectors cleaned/serviced and chances are you'll be able to live with the rear seal leak.

As for the gauges, chances are it's a wiring issue. Things like the temp and oil are real easy to check with a multi meter since they most likely work off of resistance. Just check for continuity between the sender and gauge and check the resistance at the sensor and then the gauges. Most times corrosion in the wiring is the issue and I'd assume that's why the tach acts up too.

Good luck,but they are great little motors once you get the leaks under control.

[BigAl.NZ]

Originally Posted by Mediator

Idle Speed: the techometer works very intermittently (see below) so I don’t have hard numbers, but when I first bought the boat it idled at around 750 RPM in neutral and almost 500 in gear. The engine rattled like crazy so I made a habit of increasing RPM every time I shifted into gear. I’ve since changed the idle speed, first to 1200 RPM in neutral and then, out of concern for my clutch, back down to 1000 (about 800 RPM in gear). Does this sound about right to you guys? Sometimes in forward gear at idle I’ll get the crazy rattling again, once the alternator kicks on and the RPMs drop.

Gauges: of the four engine instruments (tech, voltage, water temp, and oil pressure) only the least useful one, the voltameter, works with any degree of reliability. The tech works about half the time, and the water temp and oil don’t really work at all. Is it worth buying a new panel, buying individual guages from defender, or looking into the sending units first? I only care about the tech, water temp, and most importantly the oil pressure, because...

Hi,

I also have a 4.108 of similar vintage. We have two alternator's, but its the starter one that drives the tach. The issue that we had was a either the tach didn't go at all or the needle 'bounced'.

The alt was a Valeo and it looked very old - perhaps original to the engine. In the end we fixed it by replacing the alt. The old one ended up in a state where if the starter battery was in float it not sending out its pulses properly.

We verified this theory before changing our alternator by purposely taking some charge off the starter battery and the bouncing would go away.

The new alternator we got from Trans Atlantic Diesels (TAD) and its a Delco. (TAD are very good with 4.108 stuff).

We have it hooked up to a analog gauge,and installed a Actisense EMU-1 which puts the engine data on N2K backbone.

In terms of the temp gauges, I replaced the sender on that as I was suspicious about our temps - she runs a little hot. They are very simple devices, and replacing the sender is cheaper than getting a new panel or gauge.

And yes our engine drinks oil too. Hence the Actisense giving us oil alarm (switch) and oil pressure (sender) is piece of mind.

I have the manual here somewhere if you want a copy in PDF.

[Wainui]

I have just replaced my 52 yo 4108 with a BM 50. Big improvement
My Perkins was leaking oil from the rear main big time. I removed the transmission and fly wheel and replaced the rope seal. 10 hrs later it leaked again. The chrome journal on the crankshaft was scored so it chewed up the new seal. Definitely check yours.
I also had installed a longer HE which lowered the top temperature by 15 deg.
Good luck

[BigAl.NZ]

Don't suppose you want to sell that HE?

[Wainui]

Sure would love to
It made a big difference in temp

http://www.cruisersforum.com/forums/...le-202171.html

[lifeofreilly57]

The tach could be a normal issue, if it's alternator driven the tach may drop off intermittently when the alternator is not charging, turning on something on the boat to use power will bring it back on.
A good way to test it is to see when it goes out and then turn something on that loads the alternator, if that brings it back you know the cause. Some of the more advanced charge controllers have the tach feed on them and will maintain a small load to keep the tach working. Find out what your charge controller is and get the paperwork to look into it.
The other controls probably need to have the wiring checked or the sending units checked. I recently rebuilt the 4108 on my boat, I pulled it for just the reason your seeing, my engine leaked a quart every 8 hours, I pulled it mainly for the oil seals but rebuilt it because pulling it is 3/4 of the work and you might as well do it while you have it out. It had 4000 hours on it and when I measured the crank and cylinders everything was within spec, it could have gone 10,000 more hours easily. The only thing that might have required servicing before that were the valve guides, they were a bit more worn than I would have liked, I replaced them and installed new valves. Of course, you can pull the head with the motor in the boat.
Having the injectors serviced would go a long way.
If you don't know the service history, adjust the valves, change the oil, have the injectors cleaned, you might be surprised at how much of a difference this can make.
As for the idle issue, see which injection pump you have, if it's the hydraulicly controlled idle speed type (older) their is an adjustment for the idle speed and air. If it's out of adjustment you'll get erratic idle speeds and sometimes stalling when going into gear. It might need to be adjusted, but don't do it until you've done the other service points.
The gaskets for the valve cover, lifter cover, main timing case seal and main front crank seal can be changed in the boat. If you remove the the front timing case cover to replace that seal you'll have to re-center the raw water pump drive. To replace the timing cover seal or front crank seal will require pulling the crank damper, but it's not that hard.
These are mechanically injected motors, so they will run even if hit by lightning, which is a good thing, but making sure they're set up properly can make a world of difference in how well they run.
How good are your mechanical skills? Do you have the factory manual for it? If you don't have the manual, get one. Their a little quirky but pretty simple once you get familiar with them.

[Mediator]

Hi all,

Excellent advice everyone; I really appreciate all the expertise here.

I’m not a mechanical engineer but willing to get my hands dirty. I’ve pulled and cleaned the heat exchanger (it used to overheat) so I can do some work. Engine access on the Passport 40 is second to none. I’ll probably start with the front seals and valve cover, those look easy to do.

I’m not enthusiastic about pulling the engine. We’re putting her on the hard this winter for some bottom work, so if I’m feeling ambitious maybe I’ll tackle the motor mounts/rear seal/damper plate. Or I could just idle the engine a little higher and put down some more oil absorbent pads.

I’ll start looking into the wiring. I am suspicious about the current alternator/regulator setup - it charges far slower than it should. I’ll look into it some more next time I’m on the boat.

Thanks all,
Sawyer

[Lepke]

When you change the rear main (rope) seal you need to grease it where it comes into contact with the crank. Failure to do so will usually cause the seal to shift and start leaking. Replacement rope packing is available with lubricants built in, better than old style, but you still need the grease at break in.
These guys sell a replacement new style seal:
https://www.foleyengines.com/
Some people say they're a PIA, but I had no trouble.

I currently run a 1972 4108 on a generator. Fine engine, always starts with ease. I use SW gauges, no tach. Since rebuild uses a minuscule amount of oil. Rebuilt because of glazed cylinders, po ran continuously with light loads.
To change the rear main seal, everything behind the engine needs to be removed from the flywheel back. Pan can stay. It may be easier to lift the engine.