Connecting a PWC muffler to a Perkins 4.108-gctid391250

[Guest]

I have access to used but in very good condition muffler from a 1994 Seadoo similar to the one in the attached picture. It is rated for a 78 horsepower gasoline engine. I'm considering connecting it to my Perkins 4.108 as a part of my repower. The exhaust will be exiting from the transom, above the waterline.

Considering PWC's have a wet exhaust; and considering this muffler is rated for a 78 horsepower engine (and my Perkins is 48 horsepower), I'm wondering if there are any drawbacks to using this unit instead of a marine waterlock muffler. This unit is available locally for $30, which is 1/8th of the cost of a brand new Centek waterlock muffler.

Thanks in advance for any input.

Attached files [img]/media/kunena/attachments/vb/694860=28707-seadoo muffler.jpeg[/img]

[Guest]

For that kind of money, why don't you just buy it and try it with the motor. If it works, great. If not, throw it back out there for sale.

[2850Bounty]

Ed, I don't see why that would not work.

If the inlet/outlet OD is correct or close, give it a try.

.

[Guest]

Astral Blue wrote:
I have access to used but in very good condition muffler from a 1994 Seadoo similar to the one in the attached picture. It is rated for a 78 horsepower gasoline engine. I'm considering connecting it to my Perkins 4.108 as a part of my repower. The exhaust will be exiting from the transom, above the waterline.

Considering PWC's have a wet exhaust; and considering this muffler is rated for a 78 horsepower engine (and my Perkins is 48 horsepower), I'm wondering if there are any drawbacks to using this unit instead of a marine waterlock muffler. This unit is available locally for $30, which is 1/8th of the cost of a brand new Centek waterlock muffler.

Thanks in advance for any input.

Because diesel engines work without any restrictions to airflow you would be choking your engine with that small muffler.

Diesel engines need a muffler at least 3 times as large as a gas engine.

[2850Bounty]

Any wet exhaust muffler will offer some restriction simply due to it being wet.

The jet ski engine that this muffler came from was 78 hp.

The little Perkins is only 50 hp.

The RPM that the jet ski engine operates at is no doubt much higher than the Perkin's RPM.

Higher operating RPM should equate to a muffler design that is capable of more exhaust volume.

With the water lock style muffler, the diesel exhaust must over-come the water lift!

With the jet ski muffler, the diesel exhaust will not need to over-come as much water lift..... at least not in the same fashion!

Water Lock muffler principle;





Food for thought!

.

[Guest]

check737 wrote:
Because diesel engines work without any restrictions to airflow you would be choking your engine with that small muffler.

Diesel engines need a muffler at least 3 times as large as a gas engine.

I'm not sure I understand the second part of what you stated, indicating Diesel engines needing a muffler three times the size of gas engines because they function without backpressure?

The Centek waterlock mufflers specified for my engine are not larger than this PWC muffler. The only major difference I see is that (I believe) the PWC muffler uses baffles whereas the waterlock mufflers just use a chamber.

[Guest]

Astral Blue wrote:
I'm not sure I understand the second part of what you stated, indicating Diesel engines needing a muffler three times the size of gas engines because they function without backpressure?

The Centek waterlock mufflers specified for my engine are not larger than this PWC muffler. The only major difference I see is that (I believe) the PWC muffler uses baffles whereas the waterlock mufflers just use a chamber.

Just look at the mufflers on diesel pick-up trucks.

Same HP as gas, muffler and tail pipe 3 times the volume.

[kwb]

check737 wrote:
Just look at the mufflers on diesel pick-up trucks.

Same HP as gas, muffler and tail pipe 3 times the volume.

This is a terrible comparison for so many reasons, first water cooled exhausts, second Turbo v. NA, third not all of them are all that different.

Diesel pickup is Turbo - usually running at least 15psi of boost which means that there is roughly double the volume of air going through the engine as a NA gas engine of same displacement. A Turbo engine also needs much less muffling than a NA engine.

I say price point is low enough to give it a shot but be careful in testing things before you stop paying attention.

[itsabowtime2]

My question is the potential savings worth the risk? $30 vs. $240 on an engine that is $1,000's to replace. If it was $30 vs. $1,000, yes i would be tempted, but IMO, the $200 savings is not work the risk.

[yachtman]

I have a vernal lift exhaust muffler ill make you a deal on. It looks like the one in bounty2850 post. I took out my generator and I wont be putting it back in.

Pm me if interested.

[Guest]

kwb wrote:
This is a terrible comparison for so many reasons, first water cooled exhausts, second Turbo v. NA, third not all of them are all that different.

Diesel pickup is Turbo - usually running at least 15psi of boost which means that there is roughly double the volume of air going through the engine as a NA gas engine of same displacement. A Turbo engine also needs much less muffling than a NA engine.

I say price point is low enough to give it a shot but be careful in testing things before you stop paying attention.

I had 4 diesel tractors on my farm, none were turbo, all had oversized exhaust systems.

Even without a turbo a diesel should always have minimun back pressure to run well.

[2850Bounty]

check737 wrote:
Even without a turbo a diesel should always have minimun back pressure to run well.

Cliff, I don't think that anyone is disagreeing with you on that issue alone.

But please note that Ed's little Perkins is 50 hp, and it will be using a wet muffler no matter what!

I still suggest that if the engineers designed the jet ski muffler for 78 hp, and within the RPM range that the jet ski engine operates (much higher), it should be more than adequate for 50 hp and at a much lower RPM.

Here's a few online CFM calculators for sizing carburetion CFM requirements.

http://www.carburetion.com/calc.asp

This one allows for Turbo vs Non-Turbo in both Gasoline and Diesel.

http://www.widman.biz/English/Calculators/CFM.html

Here's a real simple calculator.

http://www.4secondsflat.com/Carb_CFM_Calculator.html

Why not use one of these calculators to approximate the CFM requirement on the incoming side?

While this may not equate to the CFM of exhaust gasses that are produced, it will at least approxiamate incoming combustion air requirements.

Add a fudge factor for the Diesel expansion, and make a rough comparison.

All Ed needs is cu in displacement and RPM, and he can plug in the numbers.

.

[Guest]

2850Bounty wrote:
Cliff, I don't think that anyone is disagreeing with you on that issue alone.

But please note that Ed's little Perkins is 50 hp, and it will be using a wet muffler no matter what!

I still suggest that if the engineers designed the jet ski muffler for 78 hp, and within the RPM range that the jet ski engine operates (much higher), it should be more than adequate for 50 hp and at a much lower RPM.

Here's a few online CFM calculators for sizing carburetion CFM requirements.

http://www.carburetion.com/calc.asp

This one allows for Turbo vs Non-Turbo in both Gasoline and Diesel.

http://www.widman.biz/English/Calculators/CFM.html

Here's a real simple calculator.

http://www.4secondsflat.com/Carb_CFM_Calculator.html

Why not use one of these calculators to approximate the CFM requirement on the incoming side?

While this may not equate to the CFM of exhaust gasses that are produced, it will at least approxiamate incoming combustion air requirements.

Add a fudge factor for the Diesel expansion, and make a rough comparison.

All Ed needs is cu in displacement and RPM, and he can plug in the numbers.

.

Rick I totally agree with you. My trouble is saying a gas engine part is ok for a diesel application without doing a comparison of the engine requirements and HP is not the one CFM is.

As you know many people will read this thread and my only thought is a non-rational approach to comparing gas and diesel applications will be made without proper research.

Cheers

[2850Bounty]

check737 wrote:
Rick I totally agree with you. My trouble is saying a gas engine part is ok for a diesel application without doing a comparison of the engine requirements and HP is not the one CFM is.

As you know many people will read this thread and my only thought is a non-rational approach to comparing gas and diesel applications will be made without proper research.

Cheers

Cliff, I hear ya, and I do agree that the correct research would ultimately be in order......... but Ed is installing a 50 hp Perkins diesel engine in a 2750 Bayliner, where previously a GM SBC was installed.

How many others will follow suit?

Now...., if Ed and I, or Ed and you were to go into production on these, we'd best do our research! :kidding

.

[smitty477]

This is interesting....

And I truely do not know the answer but I would not risk it as an experiment to find out.

I have jet skiis and I have diesels and there are quite a few differnces in the way they call for the design criteria.

Certainly waste exhaust flow and backpressure are one key as mentioned clearly above.

But how that would exactly equate to intake air between a 2 stroke jet skii turning 8,000 rpms and a non turbo 4 stroke diesel at half that I cannot value.

Then you have a few other variable 'things' to conssider:

- rating of diesel backpressure vs 2 stroke

- height of elbow above water line

- height of new muffler above/below elbow

- exhaust hose routing and potential required 'loop(s)'

- angle of muffler mounting and orientation

Most all waterlift mufflers come with some clear guidelines on hp, heights, loops, exit heights, potential heeling issues etc etc.

So no way would I be able to help without worrying that I may have indavertently contributed to the early failure of your new engine configuration.

I would error on the safe side here as there are too many potential pitfalls.

Hope this helps