Perkins 4-108 diesel

[capttman]

If you are coastal cruising years of towing insurance can be bought for cost of replacing the engine. Have the mechanic write down what he said and try to knock off 25k on the boat!! Haha
And see how that goes

[troppo1]

I would love to know how it went, I bought a 4108 that was 36years old and only had 835 hrs on it, now at 1100 hrs I have had to replace the the valve stem seals and the throttle shaft Orings, my Mechanic couldnt believe his eyes when he came to do the tappets. Never seen a 36year old 4108 lowline that ran like a new motor, which really it is, except all the rubbers will have gone hard and will be replaced bit by bit, expecting the back crankcase seal next, already have the replacement ready to go.

[oldcal46skipper]

We have re-manufactured 11 Perkins 4.108 long blocks this year. In all cases they had few hours and had failed due to owner neglect, improper maintenance, boat sunk, etc. None of these 11 failed due to excessive wear. I believe the Perkins 4.108 is one of the best mid size marine engines ever built.
Tom

[stepheno]

I know this is an old thread, and I'm considering a 4.108 for my yacht. The one I've found has no gearbox. Does the Perkins require a specific gearbox or is there a good choice of adapters, bell housing, etc.


I have a 40' 15 ton, yacht. The old motor is an 75HP Nissan SD25. Will the Perkins be okay with this size boat?


Thanks,
Stephen

[Lepke]

The 4108 will work, but short on hp. The Perkins pleasure rating is 48hp and continuous rating is 36hp. If you're mostly motoring to and from the dock, ok. But you'll probably loose a couple knots compared to the Nissan. There are usually Perkins engines and gear boxes on ebay.
It would probably be cheaper to rebuild the Nissan.
A different engine means modifying engine beds, a new alignment, probably a different prop, adapting to existing exhaust, fuel lines, shift/throttle linkage, gauges/control panel, salt water cooling and so on.

[stepheno]

Thanks Lekpe. Valid points.

I have quotes of AUD12,500 to rebuild the Nissan and so looking at alternatives. My boat is on the hard and a restoration project, running over 2 years so far. I can rework the engine bay to suit a different motor; it's fairly roomy.

Note taken of your HP comment.

[cburger]

Look closely at the starboard side of motor, our 4108 has a manual oil extraction pump attached to motor that makes oil extraction a snap.

[Cheechako]

Originally Posted by stepheno

I know this is an old thread, and I'm considering a 4.108 for my yacht. The one I've found has no gearbox. Does the Perkins require a specific gearbox or is there a good choice of adapters, bell housing, etc.


I have a 40' 15 ton, yacht. The old motor is an 75HP Nissan SD25. Will the Perkins be okay with this size boat?


Thanks,
Stephen

The 4-108 in my fairly heavy Tanton/CT44 was plenty of engine even up here in the PNW where 5 knots of current isn't unusual and up to 12 knots occur!. (My avatar) Very economical engine too, I kept track in a log the entire time I had the boat. The average over that time was .65 gallons an hour of fuel use. The boat would do nearly 8.5 knots in flat water as it had a long waterline. I had a 17" Max Prop.
We had the Hurth gearbox. They often came with Velvet Drives too... a much bigger transmission than the Hurth.

[Mike OReilly]

Originally Posted by stepheno

I know this is an old thread, and I'm considering a 4.108 for my yacht. The one I've found has no gearbox. Does the Perkins require a specific gearbox or is there a good choice of adapters, bell housing, etc.


I have a 40' 15 ton, yacht. The old motor is an 75HP Nissan SD25. Will the Perkins be okay with this size boat?


Thanks,
Stephen

My 4108 moves my 37’ 15-ton full keel sailboat quite well. Will hit hull speed (~7 knots) at around 2200 RPM. I usually cruise at around 1700 @ ~6 knots.

[Astral Blue]

Originally Posted by stepheno

I know this is an old thread, and I'm considering a 4.108 for my yacht. The one I've found has no gearbox. Does the Perkins require a specific gearbox or is there a good choice of adapters, bell housing, etc.


I have a 40' 15 ton, yacht. The old motor is an 75HP Nissan SD25. Will the Perkins be okay with this size boat?


Thanks,
Stephen

The 4.108 has a standard Borg Warner bolt pattern. This will mate to most marine transmissions with this pattern. One thing you need to check is your flywheel to ensure it will mate to the transmission you are considering. I repowered a powerboat with this engine and needed to make modifications to the flywheel to allow it to bolt to my drive.

[troppo1]

Not a hope. Stick to another 70hp. Under powered boats are dangerous.

Originally Posted by stepheno

I know this is an old thread, and I'm considering a 4.108 for my yacht. The one I've found has no gearbox. Does the Perkins require a specific gearbox or is there a good choice of adapters, bell housing, etc.


I have a 40' 15 ton, yacht. The old motor is an 75HP Nissan SD25. Will the Perkins be okay with this size boat?


Thanks,
Stephen

[sprousesan]

How much did you pay for the used 4-108?

[Boatyarddog]

Originally Posted by bsankey448

Just talked to the mechanic who did a survey on the engine. He says that a Perkins with that many hours is just about at the end of it's life span and I will need to do a re power in the not to distant future.

Maybe the engines he's built go 4000hrs.
Professional builders claim 10,000 to 12,000.
And, what's in your rebuild matters!
SV Cloud Duster