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Ralphy

Looking for Hammerhead 365 Information.

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Ralphy
Posted (edited)

Hi guys, First post on the Malibu crew page. Have been scrolling around the page digging up whatever information I can find on the Callaway 365 hammerhead. We recently purchased a 1998 Malibu response lx with the hammerhead 365 with 1000hrs on it and the hull. so far what I know about the hammerhead is:

-The stock 1998 hammerhead is based on the 5.7L

-the Hammerhead had GM fast burn aluminum heads and a different cams then the monsoon 5.7. I assume that this is the 40 horsepower difference between the classic 5.7l and the Hammerhead.

What I know about our boat:

-Boat has a jasper block allegedly installed at 400 hull hours after the original owner did a poor winterization. All jasper could tell me from the sticker on the block was that it was installed pre 2014.

-The owner I purchased it from had had it for 9 years

-upgraded it to stargazer

-It will eventually need a exhaust manifold as there is a small crack right at where the manifold bends. It drips a very small amount of water when running,  will run as is and repair at a later date.

-kept the interior in absolutely incredible condition for its age.

So my questions to any hammerhead owners are what are you seeing for top speeds and RPM? So far we are happy with the boat but I am not really that impressed with the motor. We have three friends each with responses (1 98 and 2 99s) all have the monsoon and they are basically preforming the exact same to slightly better than the hammerhead. With a acme 449 on the boat we saw 47.8 mph at 5050rpm. I know these boats aren't built for speed, they are tow boats but I was expecting slightly better speeds than the monsoon. I have a 515 on the way and that will be the prop I consistently use. The boat appears to have some sort of vibration that I cant quite figure out, the prop is in perfect shape so maybe I am just not use to the cam of the hammerhead? The boat almost feels slower out of the hole than the monsoon as well? maybe having a fuel supply issue? I plan to change the fuel filter soon and it does still have the hard lines from indmar so it does have a fuel hammering if you back off the throttle rapidly. ANY other items I should watch for on this motor? I know oil consumption has been an issue on these motors but so far no signs of that.

 

 

 

 

 

Edited by Ralphy

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Eagleboy99

FWIW, the 98 Boat Buyer's Guide (IOk - I hoard old waterski magazines... until wife finds them) clocked the 98 RLX at 51.3 mph.   The 99 Monsoon RLX we have gets 47 with a tailwind (GPS verified).  The old CVP stainless prop got even higher speeds but it is gone now...

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Woodski

@Ralphy- I would expect a closer 100 RPM : 1 mph ratio at the higher speed with the 449 prop.  Those heads flow better than the Vortecs in the Monsoon (bigger valves) and I think the cam is a ZZ4 which has more lift than the marine cam.  Question would be:  did block repair get done as a block only using the Hammerhead internals or was it a short block replacement?  I am not sure if the ECU limits fuel or spark at over 5000 rpm.

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Michigan boarder
Posted (edited)

You seem like you know your way around a boat, but first eliminate the obvious: when was the last tune up?  Have you inspected the plugs?  Compression check?  A fouled plug will cause vibration, but with all that HP at speed you can run on 7 cylinders and still have a quick boat, without vibration even.

Edited by Michigan boarder

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Engine Nut

Are you sure that when the Jasper block was installed that the cam and heads from the original engine were swapped over? The fast burn heads on the hammerhead are aluminum ... have you checked with a magnet? 

 

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Ralphy
7 minutes ago, Engine Nut said:

Are you sure that when the Jasper block was installed that the cam and heads from the original engine were swapped over? The fast burn heads on the hammerhead are aluminum ... have you checked with a magnet? 

 

I have not checked with a magnet but I am pretty confident they are aluminum. They are stamped "GM Performance Aluminum" and they are not painted and there is no signs of rust on them. As far as the cam I will have no idea if it was swapped over. I am assuming if they swapped the heads they also swapped the cam

2 hours ago, Michigan boarder said:

You seem like you know your way around a boat, but first eliminate the obvious: when was the last tune up?  Have you inspected the plugs?  Compression check?  A fouled plug will cause vibration, but with all that HP at speed you can run on 7 cylinders and still have a quick boat, without vibration even.

This has made me start thinking. I ran a compression check when I bought it,all cylinders where +/-3 from 155. But I am now wondering if I didn't get all the plug wires back on exactly as they had been. Because it is a new boat to me I think it may be a good idea to do new plugs, wires, cap, just so I have a base line of when these items had been changed.  Running on 7 would explain the vibration, the average to mediocre performance. this will be the first place I check.

 

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MopedMedicks

Hammerhead Callaway 365 hp x 7/8 cylinders = 319.375 hp. That’s pretty close to a 325 hp gen 2 Monsoon.

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Ralphy

New plugs, new cap and rotor, new wires, and two new fuel filters. Ran 48.5 with the 449 at 5210 rpm. Ran 47.2 with footer behind. Happy with the improvements!

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Ralphy

Hi guys, going to stir up an old thread. I was searching around for timing information on the 365 hammerhead. Does anyone have the base timing specs for this motor? Or have any idea on where I can find this information? The boat is running almost perfectly. The only Issue we are having is on a heavy acceleration, especially under heavy load the boat will stall and occasionally backfire. There is the odor of fuel when this occurs. So my thought was maybe the timing is off by a little bit. I also saw on a another thread @BillFooter switched his thermostat to 180 degree thermostat? Is running to cool a common problem for the hammerheads? What is the boat supposed to have in it? Any information will be very helpful.

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UWSkier

Can't help with the timing but 160F thermostat should be good.

You've got a strong motor if you're pulling 5210 RPM with the 449!

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