Motor length for Zodiac 550

DiabloLoco · 09 November 2021, 03:38

I have a 1994 Zodiac Pro II 550 with a 1994 Yamaha 90hp motor. I am not sure of the length, but what is the best size, a 20" or 25"? Thinking about getting a larger motor and want to get the correct length, since they are not cheap. Thanks in advance for any advice or help.

spartacus · 09 November 2021, 07:05

Pretty sure it will be long shaft, 20". Go with the speed rating (maximum hp) on the Zodiac transom build plate if you're looking to upgrade. Bear in mind that 90hp will be 2-stroke, so you're already getting good power to weight ratio, and 4-stroke equivalents add a few more pounds being wet-sump.

With the engine trimmed down, then the anti cavitation plate should line up with the base of the keel. You can then adjust the motor up slightly a hole at a time to get a perfect set up. Outboard propeller choice can make a heck of difference too.

To measure an outboard, go from the underside of the saddle where it mounts the transom to the top if the anti cavitation plate.

beamishken · 09 November 2021, 08:08

That 90 yam is one of the best engines ever made. I'd be very reluctant to change that if its running well, it will be a hard engine to beat

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DiabloLoco · 10 November 2021, 04:08

Quote:

Originally Posted by beamishken

That 90 yam is one of the best engines ever made. I'd be very reluctant to change that if its running well, it will be a hard engine to beat

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having issues with the motor that none of the mechanics around here can figure out. They are doing "trial and error" method of trying to fix it. That has cost me too much already. Reason for upgrading.

DiabloLoco · 10 November 2021, 04:10

Quote:

Originally Posted by spartacus

Pretty sure it will be long shaft, 20". Go with the speed rating (maximum hp) on the Zodiac transom build plate if you're looking to upgrade. Bear in mind that 90hp will be 2-stroke, so you're already getting good power to weight ratio, and 4-stroke equivalents add a few more pounds being wet-sump.

With the engine trimmed down, then the anti cavitation plate should line up with the base of the keel. You can then adjust the motor up slightly a hole at a time to get a perfect set up. Outboard propeller choice can make a heck of difference too.

To measure an outboard, go from the underside of the saddle where it mounts the transom to the top if the anti cavitation plate.

Boat is rated for a max 120hp outboard. Thanks for the advice. I will measure it in the morning.

beamishken · 10 November 2021, 08:08

Quote:

Originally Posted by DiabloLoco

having issues with the motor that none of the mechanics around here can figure out. They are doing "trial and error" method of trying to fix it. That has cost me too much already. Reason for upgrading.

Ah thats a shame but I'd be concerned about the ability of the tech if he cant diagnose a simple two stroke but I get your reasoning. Almost certainly going to be a 20" long shaft but easy to measure from bottom of keel line to top of transom. Should be around 19-22" for longshaft. Engine choice will be a lot up to brand preference or local dealer support Yamaha suzuki or mercury are all good in general probably need to go up in hp a little as those yams were strong for their size & weight

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tiverton_tom · 10 November 2021, 13:59

concur about that 90 being one of best motors every made

i have avon 620 - while completely different company/mfg - it is 20 inch

came with 115 - 20 inch - which we used a year or two

we used a 'jackplate' for a 25 inch F150 later.

90-115 is lots of power, unless carrying a lot of weight.
Adding jackplate in most cases means longer steering cable, we upgraded to hyrdaulic same time.

DiabloLoco · 14 November 2021, 04:09

Thanks for your help guys. Makes a big difference

spartacus · 14 November 2021, 21:29

Out of interest what's the faut with the Yammie 90?

DiabloLoco · 14 November 2021, 22:02

While driving the boat out, after about 5 minutes, the motor loses power and will not go past 700rpm. If i let it set at idle for a couple of minutes, I can make another run, for about 5 minutes. Then it does the same thing. I have replaced the fuel pump, replaced fuel lines, filter and the fuel. I also just removed and replaced the thermostat with a new one. Compression is even at 120 on all 3 cylinders. Spark plugs are new. The one mechanic that is an authorized dealer for Yamaha in my area is a crook and and asshole (I know him on a personal basis). All of the other mechanics that work on 2-strokes are using trial and error method to fix issues and it has cost me much more than the motor is worth. So, I have been working on the issues myself and buying parts from Partsvu.com and Boat.com. I still have to find time to take my boat for a test run since I did all of the work, but I am still trying to find a day I can go and do that.

office888 · 16 November 2021, 00:18

Quote:

Originally Posted by DiabloLoco

While driving the boat out, after about 5 minutes, the motor loses power and will not go past 700rpm. If i let it set at idle for a couple of minutes, I can make another run, for about 5 minutes. Then it does the same thing. I have replaced the fuel pump, replaced fuel lines, filter and the fuel. I also just removed and replaced the thermostat with a new one. Compression is even at 120 on all 3 cylinders. Spark plugs are new. The one mechanic that is an authorized dealer for Yamaha in my area is a crook and and asshole (I know him on a personal basis). All of the other mechanics that work on 2-strokes are using trial and error method to fix issues and it has cost me much more than the motor is worth. So, I have been working on the issues myself and buying parts from Partsvu.com and Boat.com. I still have to find time to take my boat for a test run since I did all of the work, but I am still trying to find a day I can go and do that.

Carb float problem. Bad adjustment of needle height or clogged jet. Remove the carb rack and have it professionally cleaned ultrasonically.

Matt · 16 November 2021, 09:40

I agree with all the above - the yam 90 is a good motor.

Carb setup is a good shout. You didn't give details of "how" it won't go past 700 rpm. For example, if you pump the primer bulb, does that change anything? If you turn the motor off, rather than idling, for 5 minutes - does that change anything?

On one of my old mercury V6 motors I had the high speed stator go intermittently bad - was fine when cold, but once it got hot, it broke down. A bit of idling and it cooled down again and I was good to go for a bit, again. Took me an age to diagnose that one. (Not your issue here - stator changeover speed low to high was about 2000 rpm)

Either way, Yam 90 is a good motor and worth fixing, even if you decide to upgrade - make sure the yammie doesn't get scrapped.

DiabloLoco · 19 November 2021, 22:47

Quote:

Originally Posted by Matt

I agree with all the above - the yam 90 is a good motor.

Carb setup is a good shout. You didn't give details of "how" it won't go past 700 rpm. For example, if you pump the primer bulb, does that change anything? If you turn the motor off, rather than idling, for 5 minutes - does that change anything?

On one of my old mercury V6 motors I had the high speed stator go intermittently bad - was fine when cold, but once it got hot, it broke down. A bit of idling and it cooled down again and I was good to go for a bit, again. Took me an age to diagnose that one. (Not your issue here - stator changeover speed low to high was about 2000 rpm)

Either way, Yam 90 is a good motor and worth fixing, even if you decide to upgrade - make sure the yammie doesn't get scrapped.

Good info and advice. thanks

jonp · 20 November 2021, 03:55

Long shaft on my 550 and also long shaft on my daughters 500 zodiacs. Ditch the stinky two stroke and get something you can run all day without smelling two smoke!!!!