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Jet boat restoration/mod

T

Tass 928

New member
Brief intro: My boating career has included two Checkmates, an Enchantor with a 200HP black max and a 2800OB with twin 200's. Kids, educations, other hobbies and just life in general have kept me away from boats for the last 20 or so years. One of the hobbies I picked up along the way is Porsche 928's. These are front-engined, watercooled v8 cars that are pretty much the orphans of the Porsche world.

And so, on to the current story. I have a 300hp Porsche V8 engine that I am going to transplant into a Checkmate jet boat. I have most of the details worked out and a jetmate candidate in mind. My first question, and it is an important one , is how much does an 18 ft jetmate hull weigh? 300 Hp is not much in the jetboat world...saving weight is important to this project. My goal is to get a minimum of 70MPH.

Any help from Jetmate owners or other members would be very much appreciated.


thanks
Dave T
 
Sorry, but 70 ain't gonna happen with that little motor N/A. It takes torque to spin that pump, thats why most jets have Big blocks. Now, if you are willing to break new ground, put a power adder on that thing and try a real loose impeller and spin it to the moon. Honestly, I would not do it because it would cost a ton and still be hard to achieve your goal. Oh, and 70 in a jet is not going to "Rule the River."
 
Im not sure on the hull weight but it cant be all that much.

From what I have seen, it takes big power to get 70 with a jet. A stock 350 is good for 55-60 mph.
 
According to the brochure in the gallery the boat weighs somewhere around 1600 to 1700 lbs.. assuming this represents the engine is in(putting the hull 6-700) the numbers were blury... . Alot goes into these pump boats, first you have the engine (air pump) then the water pump. 100% initial load factor + maintaining water flow.. I know the porsh cars go, but not so sure that engine's cam and related equipment are going to have what it takes to make it on the water at that speed.

I had a sidewinder long ago 18 foot started with the big block olds, got older and broker with the fords, dumb and dumber with the chevy's and the damn thing would go high 60's, and that was it..(a, b, or c impeller) it did 57 with the olds, based on the technology we had back then (YE OL GUESS N GO SPEEDO).
 
I also agree that Porsche engine needs to be left in a Porsche. You will only be pissing in the wind. It takes more Torque and HP to run a jetboat than any boat made outboard or I/O. Its even a waste of time putting a small block in one.
 
Yep, I don't think 70 mph is gonna happen in a jet with 300 HP. Jets usually ran Big block engines, something with a good amount of tork. Another thing a lot of guys forget about is the jet drive. You have to build the pump to match the horse power and tork of the engine. I'm guessing the bare hull weighs about 900 to 1000 pounds.

There are lots of web sights you can go to that will even calculate horse power to impeller size. Make sure you do you home work. Here's a few sights to check out.

http://www.americanturbine.com/

http://www.jetboatperformance.com/index.php?p=main

http://www.berkeleyjet.com/

http://www.berkeleyjet.com/impellers.aspx

http://www.performancejet.com/IMPELLERS.htm#top

Also grab a Hot Boat magazine, there's a lot of Jet Drive sources in there. I have a 72 Jetmate with .30 over 396 pushing about 500 HP. I'm doing around 70 MPH. I'm gonna put the GPS on it this summer and find out exactly. The old engine was radared at 69.8 mph.

Here's some pics of my ride. Good luck on your project.

http://checkmate-boats.com/forums/showthread.php?t=14018 :thumb:
 
Hey thanks for all the responses. :thumb:

Let me start by saying that I completely agree with all of your viewpoints . 300HP is pretty small for jet boat and a top speed of 70 is nothing to get excited about in the jetboat world. The purpose of this project is to showcase a fantastic engine that loves to rev and has good torque throughout it's range. The sound will be amazing.

I am a 928 enthusiest and one of my cars is running this engine with a centrifugal blower and air/water intercooler. If I need the extra power, I can make that happen but my starting point is going to be the stock 300 HP. Red line is 6,500 rpm.

Porsche actually dabbled in a marinized version of this engne and they were installed in jet boats. The claim was that it pushed a 28 footer to 70MPH. Now of course I think thats utter crap, but I have one of the marine kits and I think it will do a respectable job on a boat this small.

No pics of the boat yet...I am supposed to pick it up tomorrow and I don't want to jinx my purchase:sssh:

I try and post some pics of the engine. Thanks again for the responses.

Dave T
 
Tass 928 said:
Sorry guys..my "forum rules" box looks like this...guess I can't post pics for some reason. Maybe a noob thing? Need a minimum number of posts?

Posting Rules You may post new threads
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You need to be a supporting member or use photobucket to load pictures.
Click to expand...
 
That boat with that engine wont run no where near 70. I think its a totally bad idea. And please direct me to the article that Porsche ran 70 mph in a 28 foot boat with this engine.

I also had a Checkmate jetboat and I know what kind of Torque it takes to move these boats. The Porsche is a high reving Torqueless engine, it will take over 400 footpounds of torque to hit 70 mph.

You can do this project if you want to its your boat but nobody here will agree in anyway that its anywhere near a good idea.
 
Big Red said:
That boat with that engine wont run no where near 70. I think its a totally bad idea. And please direct me to the article that Porsche ran 70 mph in a 28 foot boat with this engine.

I also had a Checkmate jetboat and I know what kind of Torque it takes to move these boats. The Porsche is a high reving Torqueless engine, it will take over 400 footpounds of torque to hit 70 mph.

You can do this project if you want to its your boat but nobody here will agree in anyway that its anywhere near a good idea.
Click to expand...


I agree that there is no way they were getting 70 out of the 28 footer. The boat is really loaded with luxury crap and the HP number is inflated, they were claiming 550HP. I have a car with the same motor from that era and max power is 325 at the crank. It's a 32valve, 4-cam.

Here is a link to sale ad for the boat. I don't have the original Porsche specs at hand but this ad writer seems to have taken his notes from the original info.

http://miami.olx.com/porsche-boat-iid-60188530

The components I have were produced by Porsche in Germany to couple their engine to a jet drive. I have factory water jacketed exhaust manifolds, a closed loop coolant system and a special bell housing with splined shaft coupler. The new porsche museum has a twin turbo'd version of this motor on a stand and a complete hydroplane type boat hanging from the ceiling with the engine installed.

They did a lot of research and made a lot of cool parts for a project that eventually fizzled out. All I'm trying to do is recreate a bit of this interesting 928 history. My end result may be a performance disaster when compared to state of the art jet boats, but it will still be a great piece for a 928 collector like myself.

I do appreciate your opinions and comments. Don't be to hard on me when I appear to ignore good advice and forge ahead anyway :cheers:

Thanks
Dave t
 
How much torque and Horse power do you think you will get out of that engine when you are finished with it? Do you know what the cubic inch is? What's the bore and stroke, max rpm, and what rpm range will it develop the maximum horse power and torque when your done? This is all important for the pump to do what it has to, to move that boat.

I'm kinda interested in how it will turn out. I'm Chevy Big Block Fan, but I like odd ball stuff a lot too!! Still would like to see some pics of your Jetmate and engine. Mine is in the picture this section under vintage Vintage Jetmate.

Good luck on your project. Sounds like you already have a lot of the marine parts you need to get started.
:cheers:
 
Boat is here!

Well I just got back from picking up the jetmate. I think I got a pretty good deal (1,200) considering it's overall condition and the fact that it is 100% complete. The boat has no damage anywhere. The gelcoat is tired but I did not intend to go with the original color anyway. The engine (460) turns over but wiring issues keep it from starting. I'm not using the engine but having it in place answers a lot of the plumbing questions I had. The trailer is usable but about as ugly as trailers can get. It looks more "cabin cruiser" than sport boat. Wood appears decent but I had counted on gutting it anyway.
The owner was a real nice guy. Seemed a little bummed to see it go.
I'll post some pictures of the boat, engine and some dyno charts as soon as I figure out how to make that happen.


Dave T
 
A few things...;)

1.. I do agree 70mph in a jet boat takes some work to nail. It needs big power & Rpms.. 300hp will probably get you around 50-55mph depending on where your weights overal come in. You will also need to adapt the Porsche v8 to a jet pump & make the engine's efi system run in a marine environment as well as get a marine wet exhaust for it. all difficult to do.. It would be unique & cool though from a wow perspective..

That said..

It is true that there were a few Porsche v8 marinized engines done. It was done in the 80's with the use of the older 928 engine. They were put into a Tempest hull & did run well & it was pretty quick.. The boat was a mean machine for what it was.. ( I think there is a picture of one of these boats with the Porsche V8 928 base in the book Muscle Boats, by Henry Ramusen. I believe the boat was silver with clear engine hatches ).. ;)

The reason you don't see it done now & why there wasnt more of them to see back then other than a small few....

COST...... It isnt that they were bad, but they were very expensive in comparison to GM marine v8 power, even though they were light & packed with power in comparison to most other non SC v8's back in the day.. There wasn't enough volume to bring the $ into being more sale able..

I am pretty big into Porsche stuff my self. I have one now & have had several others. We also do work on them & customize them as well. I have been doing it for many years. I actually used to do diag for Porsche many years ago. Cool vehicles.

I'm not sure what platform Porsche v8 you are looking to with as I don't know if your engine is out of a 928 or a Cayenne. But it would be cool to see matrerialize, I just hope you have a lot of know how from an engineering perspective to do it, as you will have your work & wallet cut out for you.. ;)

Keep us posted if you continue into doing it, while it may not achieve all that you are looking for, it would be a unique piece.. :)


:) Jamie / Lakeside


.
 
Tass 928 said:
Here is a link to sale ad for the boat. I don't have the original Porsche specs at hand but this ad writer seems to have taken his notes from the original info.

http://miami.olx.com/porsche-boat-iid-60188530
Click to expand...

Actually, that is not the one I was thinking of, but they are almost correct in the listing. The boat is rare, but there were a few others out there. The one made By tempest in the 1980s was what I was thinking of. Also, there is also a boat company called Fearless. It was designed by Porsche, built by Donzi for them & did not have Porsche power in it.. lol .. These were done a pretty recently & within the last few years before the economy tanked.. ;) Jamie / Lakeside

Below is a pic of the Fearless that was recently done.. If I find o pic of the Tempest I will post it as well.. I would have to go looking in my library for the book that it is in..
 

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LAKESIDE HE HAS THE HARD STUFF TO FIND ALREADY

The components I have were produced by Porsche in Germany to couple their engine to a jet drive. I have factory water jacketed exhaust manifolds, a closed loop coolant system and a special bell housing with splined shaft coupler.
 
Big Red said:
LAKESIDE HE HAS THE HARD STUFF TO FIND ALREADY

The components I have were produced by Porsche in Germany to couple their engine to a jet drive. I have factory water jacketed exhaust manifolds, a closed loop coolant system and a special bell housing with splined shaft coupler.
Click to expand...

:confused::confused::confused: :sssh:

No need to shout or get upset at me.. Maybe, you didn't realize I read the post where he did say that..

I guess that I probably should have elaborated a bit more on what I was talking about before. Like about hard to find things, custom things, etc...... I didnt realize that I may have confused or offended anyone.

I had seen where he found stuff to work with, however it will really depend on which variation he is actually working with. Also on this type of project there are always unforeseen things that you will run into that you usually have not thought of on that type of project.

Thats what I was trying to convey.. Thats all.. :surf:

Jamie


.
 
Lakeside Restorations said:
:confused::confused::confused: :sssh:

No need to shout or get upset at me.. Maybe, you didn't realize I read the post where he did say that..

I guess that I probably should have elaborated a bit more on what I was talking about before. Like about hard to find things, custom things, etc...... I didnt realize that I may have confused or offended anyone.

I had seen where he found stuff to work with, however it will really depend on which variation he is actually working with. Also on this type of project there are always unforeseen things that you will run into that you usually have not thought of on that type of project.

Thats what I was trying to convey.. Thats all.. :surf:

Jamie


.
Click to expand...

Not upset here, I would sell the parts and build a BBC. It reminds me of that 69 Chevy truck I seen awhile back. I guy restored the whole truck and stuck a 4cyl. Perkins diesel in it. He said it would run around 55 mph but got around 40 miles to the gallon.
 
No problem & cool .. :)

I too think it would probably be less costly & less time consuming to do a BBC application. However it would not be quite as unique.. :) J
 
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