Regular parts replacement

[groran]

Hello, I'm new here and new to boating. As I scan the forums or other info, I notice what seems to be regular postings of major parts replacement on a regular basis. Like exhaust items or heads or worse needing complete engine overhaul or replacement. Is this to be expected or is this a rare thing or say engine break down due to wear? I see the engine ingested water a lot. What causes an engine to ingest water? I'm looking at a 39' boat with twin Cummins diesels v504. I'm going to be in saltwater all the time and the boat will be moored. I wanted diesel due to the fuel economy. But then I read that they are so heavy the boat can't plane out with v504's. Seems like, with factory spec engines, the boat could plane. That may be due to the engine not getting up to full power I figure. Any advice is appreciated.

 

[RT Firefly]

Greetings,

Welcome aboard. Yep. Major work IS needed in some cases and members post about that. Seldom do they post of the tens of thousands of hours cruising without incident. A properly designed and maintained marine engine can easily run for decades with the only failures being the bolted on bits (alternators, water pumps, starter motors, heat exchangers, fluid coolers etc.)


NOT uncommon for some engines to run for 15K to 20K hours before major work being needed. It is said more engines die from not being used enough than being used too much.


That 39' boat that won't plane my not be designed to plane no matter how much HP it has (full displacement hull).

 

[Comodave]

Welcome aboard. In salt water there will be more routine maintenance than in fresh water. Things like exhaust risers will be on a 5 year or so replacement. Things rubber like impellers may be a year or two. There will be a curve bringing the boat and engines up to speed so the maintenance in the first year or two will be more intense. Not sure what HP those engines are or what boat you are looking at. So it will depend on the boats design and what power is in it whether it will plane or not.

 

[groran]

type of boat

Welcome aboard. In salt water there will be more routine maintenance than in fresh water. Things like exhaust risers will be on a 5 year or so replacement. Things rubber like impellers may be a year or two. There will be a curve bringing the boat and engines up to speed so the maintenance in the first year or two will be more intense. Not sure what HP those engines are or what boat you are looking at. So it will depend on the boats design and what power is in it whether it will plane or not.

1977 Uniflite 39’ Sportfisher. the twin 504 Cummins claims 400hp for both. The seller is claiming these specs.5.6 mph at idle
8.9 mph at 1200 rpm
12 mph at 1900 rpm
full throttle - 18 mph planing

 

[2savage]

A properly designed and maintained marine engine can easily run for decades
.

My detroit diesel is a 1969 engine, original to the boat but several rebuilds. Figure $15,000 for a rebuild. Then good for at least 10,000 hours with proper maint.

 

[Comodave]

1977 Uniflite 39’ Sportfisher. the twin 504 Cummins claims 400hp for both. The seller is claiming these specs.5.6 mph at idle
8.9 mph at 1200 rpm
12 mph at 1900 rpm
full throttle - 18 mph planing

Uniflites are not light weight boats. 400HP for a 39’ Uniflite would be marginal IMO if you intend to cruise it on plane. 18 MPH for full throttle isn’t very fast because you don’t want to run it at full throttle for very long. We have 900HP for our 41’ Formula. It cruises at 27MPH running 2200RPMs. If you will be happy at 10 to 12MPH then it would be fine. But only you can decide if that speed is good long term.

 

[mvweebles]

I gotta ask....how the hell can a sport fisher top out at 15-16 kts (18mph)?

Something doesn't make sense. For a SF, that's low for cruise let alone WOT

Peter.

 

[High Wire]

I gotta ask....how the hell can a sport fisher top out at 15-16 kts (18mph)?

Something doesn't make sense. For a SF, that's low for cruise let alone WOT

Peter.

In 1977, it was better than gas. Cruise in the teens was normal.

 

[JSK55]

Actually those numbers seem about right to me. That boat and engines (V504NA) being of 1977 vintage the hull probably plans at about 14 MPH plus or minus. Tolly's of that era run about the same numbers.

 

[mvweebles]

I guess you're right - 200hp each. No idea why anyone would buy a SF that was such a slug. Must be a convertible or something.

https://barringtondieselclub.co.za/cummins/v378-v504-and-v555.html

Did Uniflite even make a 39-footer? I owned a 1975 42ACMY, and I remember 36-foot hull, and a 37-foot hull. 39-foot doesn't ring a bell.

Peter

 

[Lepke]

v504s are a natural (no turbo) of about 200hp. They were used in tractors and industrial equipment like graders, etc., besides marine. If you're looking for parts, try farm and industrial suppliers first because they'll be cheaper than marine. They are a very common, reliable engine with proper maintenance and sensible use. A rebuild engine kit is about $1700. So if you're a mechanic and have a service manual, you can overhaul it yourself. The engine has sleeves so a kit includes new pistons and sleeves that will restore an engine to like new without boring, unlike a car engine that doesn't have sleeves.

The salt water side, heat exchanger needs to be flushed ever year or two with Rydlyme or Barnacle Buster to remove marine growth. Like others said, you have a rubber impeller in the salt water pumps that needs to be inspected every year. You don't want to let it get old enough to come apart and plug your heat exchanger.

 

[Group9]

Greetings,

It is said more engines die from not being used enough than being used too much.

.

I've lost count of how many marine mechanics have told me that.