Right sized engine for my boat

DiabloLoco · 26 August 2019, 17:16

I have a 1995 Zodiac Pro II 550. I presently have a 2-stroke 1994 90hp Yamaha on it. I am looking to upgrade the engine. The information plate on my transom says MAX HP is 120. What I am not sure about is the weight is designed to hold. Is the 120hp max recommendation based on a 2-stroke weight or a 4-stroke weight? Or is the limit based on power. I do not want to end up damaging my transom because I make a wrong decision.

Bern Hanreck · 26 August 2019, 18:49

Have you tried asking Zodiac for a definitive answer to your question rather than asking for opinions on here . They may have a different answer for a boat approaching 25 years old or might want to actually inspect it before giving an answer ( that might stand up in court ! ). Genuinely curious to know !

DiabloLoco · 26 August 2019, 23:19

Quote:

Originally Posted by Bern Hanreck

Have you tried asking Zodiac for a definitive answer to your question rather than asking for opinions on here . They may have a different answer for a boat approaching 25 years old or might want to actually inspect it before giving an answer ( that might stand up in court ! ). Genuinely curious to know !

I live in the USA. Calling Zodiac in France is not going to happen. It would be a very expensive call. I have asked 3 Zodiac dealers here in the US and they are not sure, as they don't deal with boats as old as mine, other than to do repairs. They are also concerned about liability, telling me something wrong and then having me suing them.

So, I ask people on this board what they might know or have experienced. There is a lot of info to be found here, that dealers can't or will not tell you, due to liability issues.

jonp · 27 August 2019, 01:47

Personaly I would be looking at the Yam f90 or Suzuki 90 as the minimum but either of those two manufacturers in the 115 as the max. Remember it comes down to correct propping and normal carrying loads. If you are mostly 2-4 people joy riding then your requirements will be different than 5 people scuba diving with two tanks each and dive weights etc. Both a 90 and 115 will push either weight load, however the smaller engine will need less pitch in the prop and therefore be slower.

DiabloLoco · 27 August 2019, 04:42

Quote:

Originally Posted by jonp

Personaly I would be looking at the Yam f90 or Suzuki 90 as the minimum but either of those two manufacturers in the 115 as the max. Remember it comes down to correct propping and normal carrying loads. If you are mostly 2-4 people joy riding then your requirements will be different than 5 people scuba diving with two tanks each and dive weights etc. Both a 90 and 115 will push either weight load, however the smaller engine will need less pitch in the prop and therefore be slower.

Usually, 3 divers, 6 tanks, gear and ice chest

smallribber · 27 August 2019, 07:22

Quote:

Originally Posted by DiabloLoco

I have a 1995 Zodiac Pro II 550. I presently have a 2-stroke 1994 90hp Yamaha on it. I am looking to upgrade the engine. The information plate on my transom says MAX HP is 120. What I am not sure about is the weight is designed to hold. Is the 120hp max recommendation based on a 2-stroke weight or a 4-stroke weight? Or is the limit based on power. I do not want to end up damaging my transom because I make a wrong decision.

The old is it weight or power re the transom is a very good question that is seldom answered. The issue was with so many older boats heavy four strokes were not thought about. Are you able to get a nice 115 second hand 2 stroke as that would be ok re both weight and power ?

jonp · 27 August 2019, 08:11

30-40kg difference isn't going to make much difference at all. Most new ones here in Australia are fitted with 4 strokes to the max power. Think you will find it goes of kw power not weight, it does on mine.

mhb100 · 27 August 2019, 22:09

Quote:

Originally Posted by jonp

30-40kg difference isn't going to make much difference at all. Most new ones here in Australia are fitted with 4 strokes to the max power. Think you will find it goes of kw power not weight, it does on mine.

Hi, I had a similar zodiac 1998, and that was something like 163kg transom weight , so really for 2 stroke design. I think the weight was stated in the handbook so hopefully someone will have a copy to confirm. It had been fitted with a Honda 90bf 4 stroke that was about 30kg over the weight although I did not know that at the time of buying. Spoke with a zodiac dealer and was told the transom was upgraded around year 2000. Personally I'd stick to the weight you have and avoid any insurance issues. Good luck

jonp · 28 August 2019, 06:25

According to the info I got, this is the weight and power for the mk2 550, which the engines I mentioned earlier all come under.

cgoing · 31 August 2019, 02:34

I had an older Pro 530 with same weight rating. Having a good connection at Zodiac at the time, i was told it that since most outboards back then were two stroke stick to an outboard less than weight of a 120hp two stroke.

DiabloLoco · 31 August 2019, 02:50

Quote:

Originally Posted by cgoing

I had an older Pro 530 with same weight rating. Having a good connection at Zodiac at the time, i was told it that since most outboards back then were two stroke stick to an outboard less than weight of a 120hp two stroke.

That is the answer I have been looking for. I figured that in 1995, when they build my boat, they did not have these 4-strokes like today, only 2-strokes. So, they based the rating on what was the current technology in engines. The only 120hp at that time was Force. Thank you for confirming what logic dictated.