Turbos and Boat engines

Renegade_Master

Renegade_Master

Well-Known Member
Joined
27 Jan 2003
Messages
4,434
Location
Spain
Visit site
Why is it that Turbos on boats are so bloody unreliable? yes I know they work in a salt water environment, but that alone cannot excuse them.

You get two identical engines with turbos lets say a Cat 3126 like on my new jet boat,
put one i a car/lorry and one in a boat. Drive for approx 350 hours and guess which one will need replacing.

By the way in this case cant blame it on the old "boat engines are under different strains" chessnut cos with waterets unlike props, the engine does not have suffer from such strains.

Is there anyone who has owned the same boat for say 3 years, single or twin, who has not had to attend to turbo problems? ................rant over
 
In a truck the engine
The max Hp rating is lower
The engine runs on salt free air
When the engine is running it probably averages 40% of max power rating
The engine runs on clean fuel because it gets through several tanks full a week
A truck engine often runs for 40 hrs a week every week of its life



In a boat the engine:
Is often uprated Hp per litre compared with a truck
the engine runs at a much higher continual load cruising say 75% max rating
The turbo runs on salt laden air
The fuel sits in the tank for up to 8 months
The boat engine rarely runs and when it does it goes from cold to 75% rating
Boat engines offten do between 50 and 100 hours a year
 
turbo's

We have two prehistoric Ford Sabre 180's in our Aquabell, they do about 400 hours a year, mainly fishing trips, the turbo's to my knowledge have been trouble free for 13 years, and prior to that not sure but they were commisioned in 1973, we got them second hand in 1996. Plus they run on old fashioned oil none of your synthetic stuff. They are never hammered too hard generally at 2100 were the max is 2450, she is not a high speed vessel though only cruises at 14 knots for those revs.
 
turbos and boat engines

We had four boats with turbo diesels the first was a
fletcher zingaro single ad 40 with 165 hp I think then
sealine 328 twin ad41 then sealine 350 fb twin kad 42
then princess 440 twin tamd 73p edc and never a single
problem except for one ecu unit on one of the 73p s,

dont think stale diesel fuel has any influence on the turbos.

Always in turbo engines whether petrol or diesel warm up
slowly and cool down slowly.Also always use the best engine
oil possible,personally i think shell
 
Bandit said:
In a truck the engine
The max Hp rating is lower
The engine runs on salt free air
When the engine is running it probably averages 40% of max power rating
The engine runs on clean fuel because it gets through several tanks full a week
A truck engine often runs for 40 hrs a week every week of its life



In a boat the engine:
Is often uprated Hp per litre compared with a truck
the engine runs at a much higher continual load cruising say 75% max rating
The turbo runs on salt laden air
The fuel sits in the tank for up to 8 months
The boat engine rarely runs and when it does it goes from cold to 75% rating
Boat engines offten do between 50 and 100 hours a year
Click to expand...


Take on board your points however as I said this engine does not have the same loads a prop engine has. The fuel is regularly used cos its trip boat, it gets warmed up just getting out the Marina, during the season she is used every day, regarding hours good point most boats dont do more than 50 to 100 per year.

All that said Turbos on boats are **** grrrrr
 
Sun_Coast said:
Take on board your points however as I said this engine does not have the same loads a prop engine has. The fuel is regularly used cos its trip boat, it gets warmed up just getting out the Marina, during the season she is used every day, regarding hours good point most boats dont do more than 50 to 100 per year.

All that said Turbos on boats are **** grrrrr
Click to expand...

All the same, the engine in the jet boat is still producing a much higher power output than the truck engine. The more power you extract from an engine, the shorter it's life. The jet boat engine may not have a prop to drive but it's driving a big pump
 
You cannot say that all turbo's in boats cause trouble... loads of them run for 10's of years trouble free... and sorry to hear about your trouble...

We demand more and more from our engines and we rely more on technology and aids to extract higher output from smaller blocks at lower weight, increasing overall strain on the engine parts...

Now... back to the turbo ... which spins at a rather high RPM ... which means that the most sensitive issue is oil and lubrication.... not helped by turbo being at end/late of oil flow route from pump...... so bringing an engine up from standstill to 1000 RPM at startup and low oil pressure could be a real killer... so startup procedures is essential... Never bring engine up above idle, until oil pressure is brought up ... or perhaps think about cranking engine for 5 - 10 sec., with fuel shut off (stop solenoid activated), just to get the oil circulating and start building up that vital oil pressure... getting that extra drop of oil in there that little bit earlier..

Engine manufacturers today will see a turbo as a consumable and to be replaced, so is not made to be easily re-built, but to be replaced.

I know this does not fix your engine... but may help someone prevent turbo damage...
 
Last edited:
Another point worth noting is that in a truck engine the turbo has cool air flowing over it as the vehicle moves along; no such luxury for the turbo in the boat which has to cook in an oven with (relatively) little airflow.

Given the already high temps it's already operating in, it could make all the difference especially for the bearings when the engines are switched off after a run. Are they cooking? Are they getting enough oil flow?

Even if the air through them is salt laden, if it's properly filtered that shouldn't make too much difference I wouldn't have thought.. unless the reason for the failures has been corroded turbine blades?

It would be worth looking further into the failure modes you've experienced, they should give you some pointers as to how you might prevent further problems, or at least delay them.

Good luck with the next one..

T
 
Turbo durability

Actually turbochargers have easier life on a marine engine.

Most have water cooled turbine housings, marine engines have steady temperature gradients unlike automotive engines where true steady state running even on motorway duty cycles are not really steady state.

The problems you have are;

#1 CAT 3126 is fundamentally an engine of very poor base design. IF you have the mid, low mount turbo location, one answer is staring you right in the face. CAT finally got religion when they did radical re-design of the exhaust manifold and put it in the logical place at the rear of the motor with a higher location.

CAT also tend to use KKK marine turbochargers which are renowned for having turbine housings of bizarrly poor quality iron, hopeless in marine enviroment.

#2 Poorly designed fuel systems are my pet hate, however the design of marine exhaust systems is not far behind.

Take the likely turbo location, couple this with a possibly suspect turbo material then add the chance of a marginal exhaust system into the mix and fair chance that you will continue to replace turbos.
 
Last edited:
There are various different ways that Turbos can "fail" - each failure will have it's own set of possible causes.

e.g.
Broken blades: Foreign Object Injestion, manufacturing defect
Corroded blades: installation problems, design problems, salt water getting into the airstream somehow
Bearing Problems: oil feed issues, repeatedly stopping without allowing to cool
Variable geometry turbos have a load of additional moving parts that can gum up or jam...

dv.
 
Well to answer your original question, the turbo on our KAD 32 is almost 7 years old with no problems yet.

We have owned the boat for a year, however know her previous owner had her for 6 years trouble free and we have had no trouble this year having done over 300 hours.

So yes you can have a trouble free turbo
 
How is the boat used? Is it thrown about like alot of jet boats are? Is the oil pump picking up air in the sump as the oil sloshes about in there? Turbos don't like any interuption in oil flow at the speeds they run at.

How is the exhaust system run? Is there any chance of sea water being able to enter the turbo when suddenly slowing down?

In my experiance the common turbo faults occur in outdrive driven boats where the sea water level always quite close to the turbo. The Volvo Kad engines seem to be most prone to this problem causing the supercharger to cut in and out just as the turbo should take over.
 
aquatom said:
...causing the supercharger to cut in and out just as the turbo should take over.
Click to expand...

Huh?

The main situation I am of aware of that can cause a problem in a KAD outdrive boat, is if you do an "emergency stop" and power off the engines at the same time - water can come back up the exhaust pipe.

dv.
 
Sun_Coast said:
Why is it that Turbos on boats are so bloody unreliable? yes I know they work in a salt water environment, but that alone cannot excuse them.

You get two identical engines with turbos lets say a Cat 3126 like on my new jet boat,
put one i a car/lorry and one in a boat. Drive for approx 350 hours and guess which one will need replacing.

By the way in this case cant blame it on the old "boat engines are under different strains" chessnut cos with waterets unlike props, the engine does not have suffer from such strains.

Is there anyone who has owned the same boat for say 3 years, single or twin, who has not had to attend to turbo problems? ................rant over
Click to expand...

Me. Previous 2 boats both had turbos, no problems in about 15 years. And did about 300 hrs per year. But they were both Ford Mermaids so not overly stressed.
 
A good rant

In the 1960's I was involved with fitting and testing the ford truck engine with a turbo the results were stunning a 50% increase in power coupled with a 99% reduction in service life. Obviously that changed as we learned what broke and why but the turbo was the weakness in may respects.

They obviously put more stress on the main components because of the extra power generated and fail they do - I ask you why do you want a thing spinning at 23,000 rpm or more on a boat thats pitching and yawing? its got to fail. (Take a look at the warranty they give the turbo) So I will never have a turbo on a boat.

The trouble is designers just cant resist the power to weight ratio the dreaded turbo promises and in power boats in particular the end result is an engine (s) that must be run flat out for most of its short life in order to meet the requirement, but hey thats what the custome wanted! Ragged edge engineering.
 
Please excuse me if this is slightly off topic, why dont boat builders fit superchargers to their engines, i believe they are more reliable than turbo's, or am i wrong?
regards
Tony
 
Tank said:
Please excuse me if this is slightly off topic, why dont boat builders fit superchargers to their engines, i believe they are more reliable than turbo's, or am i wrong?
regards
Tony
Click to expand...

You are correct as far as the booster is concerned but superchargers dont get their power for free, turbo chargers make use of the power in the exhaust stroke to spin the turbine, superchargers sap "good" power from the crankshaft so are thought to be less efficient.

Turbo chargers need high exhaust gas velocity to work hence they tend to "cut in" at higher revs, superchargers pump air relative to crankshaft revs so there is no abrupt cut in of power, the boost is present throughout the rev range. Turbos have turbo lag - but that is more noticable with road vehicles.

However what ever boost device you use a boosted engine is still producing more power than the normal aspirated version so it's under more stress and will wear out faster.
 
>it's under more stress and will wear out faster.
Than what? A cruise ship engine?

You won't find many modern engines that have a turbo and non-turbo version with exactly the same cylinder heads, pistons, conrods, injection systems etc. so it's almost a meaningless statement.

If you are comparing two engines of the same output, the non turbo one will be much heavier, and of little interest to the average leisure boater.
 
You must log in or register to reply here.

Share this page

Top