Zodiac Pro II 470 engine installation

[ssobol]

I have a Zodiac Pro II 470 with a Yamaha 40hp engine on it. The spec for the boat says that the engine should be a long shaft. According to the Yamaha owner's manual the motor should be installed so that the anti-cavitation plate is even with the hull bottom when the engine is down. I have noticed that on my boat the fin (?) at the front of the lower unit (about 4" above the anti-cavitation plate) is even with the bottom of the hull. The anti-cavitation plate is a few inches below the bottom of the hull. The motor on the boat is already raised up on the transom about 1.5" (the hooks on the motor mount are not resting on the top of the transom). The motor is mounted with bolts that go through the transom.

I cannot trailer the boat with the motor down. If the motor is in the normal position the skeg is about an inch (maybe a little less) from the ground with the boat on the trailer.

It seems that the spec for the boat is incorrect.

I have run the boat several times and it works fine. Goes just over 30mph with just me in it.

I bought it used from a dealer that only does inflatable boats. It was set up this way when I got it. It is probably not worth changing the motor, but I might consider changing the lower unit for a short one.

Are there any particular advantages to doing this, or should I just leave things alone?

 

[azzurro]

Re: Zodiac Pro II 470 engine installation

I have a Zodiac Pro II 470 with a Yamaha 40hp engine on it. The spec for the boat says that the engine should be a long shaft. According to the Yamaha owner's manual the motor should be installed so that the anti-cavitation plate is even with the hull bottom when the engine is down. I have noticed that on my boat the fin (?) at the front of the lower unit (about 4" above the anti-cavitation plate) is even with the bottom of the hull. The anti-cavitation plate is a few inches below the bottom of the hull. The motor on the boat is already raised up on the transom about 1.5" (the hooks on the motor mount are not resting on the top of the transom). The motor is mounted with bolts that go through the transom.

I cannot trailer the boat with the motor down. If the motor is in the normal position the skeg is about an inch (maybe a little less) from the ground with the boat on the trailer.

It seems that the spec for the boat is incorrect.

I have run the boat several times and it works fine. Goes just over 30mph with just me in it.

I bought it used from a dealer that only does inflatable boats. It was set up this way when I got it. It is probably not worth changing the motor, but I might consider changing the lower unit for a short one.

Are there any particular advantages to doing this, or should I just leave things alone?

I believe that engines must always be trailed in a tilted position to avoid stress on the transom. Just get a transom saver to ensure the engine does not move.

I'm sure a short leg engine will not work. Probably the motor is bolted up that way to avoid some splash. Put some wood between the transom top and the stern brackets if you do not like the way it's secured.

 

[Syzygy]

Re: Zodiac Pro II 470 engine installation

SSOBOL,

What year is your Pro II 470? Last two digits of the serial number. Earlier versions of the Pro II 420 and Pro II 470 required a short shaft motor. If you tell me what year your boat is (or give me the complete serial number) I can give you a little guidance.

Syzygy

 

[Syzygy]

Re: Zodiac Pro II 470 engine installation

ssobol,

I found an earlier image of your transom and the serial number. Your boat appears to have been built in 1997 and is a 1998 model year. That would mean your Pro II 470 would require a short shaft motor (15" leg), NOT a long shaft motor (20" leg). Your boat was built before the higher transoms were used by Zodiac.

Whomever set it up that way, did not measure the transom, which is likely between 15"-16.5" in height where the motor mounts. They sold you the wrong motor for that boat.

Best bet is to raise the engine with a jack plate or to modify the transom so that the engine you have fits it properly.

Syzygy

 

[Sea Rider]

Re: Zodiac Pro II 470 engine installation

Cheaper and faster is to buy an engine transom mount than modifying transom height or changing long for short shaft leg. I had the opposite problem with my 420 rib, long shaft transom with a short leg engine, finally ended cutting transom 5" down, state of the art, works perfectly.

Happy Boating

 

[ssobol]

Re: Zodiac Pro II 470 engine installation

It seems that whoever had the boat before me were the ones that got the wrong engine. The boat is a '98 model and the motor is an '06. I got the boat in '10. I boat the boat from a dealer who changed the console and detailed the boat, but they did not do anything with the motor (I saw the boat before they cleaned it up).

The question I have is while the boat runs fine as it is, are there any particular issues I should be concerned about with having a long shaft motor on a short shaft boat? Is it worth doing something to correct this? What are the advantages of switching to a short shaft motor?

The boat goes fast enough as it is, so changing the motor in order to increase the boat speed is not something I'm interested in. However, if there is a noticeable increase in fuel economy I might consider it. It seams that with the prop running deeper there might be an efficiency improvement as far as the propeller is concerned, there is also less likely hood of ventilating the prop in turns or from wave action.

 

[ssobol]

Re: Zodiac Pro II 470 engine installation

Clearly the motor is too long. However, most of the Yamaha 40's seem to be 20" shaft length. Where/how is the shaft length measured? Can I measure this from the exterior of the engine?

 

[Sea Rider]

Re: Zodiac Pro II 470 engine installation

If you have a long shaft engine mounted on a short shaft engine will probably have water splash issues side to tubes or even worst againt back transom and entering middle transom (side of engine) that's probably the water in you had and haven't seeing it while boating ? Water splashes gives more tail resistance/drag against water as flow might not be passing through triangular shaped lower leg which is ideal for max spped and general performance once on plane, if so, will lose some general speed and worst, consume more gas while on plane. 20" shafts are too long for 15"-16.5" height transoms.

You are experiencing good power because you have a 40 HP, if you had a smaller 25/30 engine mounted will see the power lose from water splashing issues. See bottom pics for refference. Check same issue treated on non repair outboard discussion, read 3 post down page. http://forums.iboats.com/showthread.php?t=503688

Sorry to give same repetitive answers, there's a lot of guys that asks issues about ideal engine height, or that have long shaft engines mounted on short transoms or viceverse, but all of them are jumping the fence with this very important proper height issue if wanting boating cruising perfection.

Happy Boating

 

[ssobol]

Re: Zodiac Pro II 470 engine installation

Sea Rider,

Thanks for the pictures.

I have not had any issues with water entering the boat hull since I put an o-ring on the hull drain and caulked the aft end of the tube slots. At speed, I have noticed a spray that comes from the front of the engine shaft that goes out to both sides and hits the back end of the tube cones, but this does not enter the boat.

The attached pictures show the engine on the boat. You can see that the motor is raised up about 3 inches on the transom (higher than I first said). This means that the lower unit is only about 2 inches lower than it should be.

Since the motor is only a little low, I would think that it might be more trouble than it is worth with trying to get it up higher.

View attachment 106118View attachment 106119View attachment 106120

 

[Sea Rider]

Re: Zodiac Pro II 470 engine installation

Attachments are not visible, why don't you perform the proper height test and check the flow, if you need to rise the engine and if your stern brackets have slots so engine moves vertical without making new holes, probably could add a wooden shim under engine where it sits on transom to compensate appropriate height raise, but that's a wild guess, know this is a tedious work, but once you have engine set at correct height the better performance achieved at plane/wot speeds it's worth the extra job.

Test actual conditions at sea, will not gain anything measuring as stated, it's a dry talk, boat's hull shapes and engine's lower legs are not same between brands and behave differently even on same boat. This pic shows a modified transom height, the sib came with 38 cm height, had awfull performance, excesive water splash inside deck no matter how well was top inflated or weight distributed forward, transom was raised to 40 cm height, now performs excellent, best top speed compared to before, check perfect water flow at turn, can see the small upper plate out of water at mediun speed. Boater has now sideburn to sideburn smile

Happy Boating

 

[ssobol]

Re: Zodiac Pro II 470 engine installation

The motor mount has slots at the lower end and a series of holes at the top. While I could move the lower bolts higher to be able to slide the motor up in the slots, the bolts at the top are already close to the top of the transom, so there is no room to move the upper bolts without extending the transom.

 

[Sea Rider]

Re: Zodiac Pro II 470 engine installation

In that case check stainless steel transom motor mounts that closes the gap, and forget rising transom. Is it possible to post some pics of transom slots arrangement ?

Happy Boating