Replacing one engine in a twin setup

[pharaoh]

Hi,

I have two 1989 Yamaha 2-stroke 115's on my boat at the moment. One of the engines requires a LOT of work, around $4000-$5000 worth. And then how far away is the other one from going.

I am weighing up my options, do I purchase 1 brand new engine now and keep the stuffed one for what spares I can salvage to keep the other motor going, or do I purchase another of the same vintage second hand, or do I have to replace both engines.

I have had conflicting advice, one person said you need to replace both unless you can find an identical year/model because otherwise you will end up in more trouble having two different model engines on, and another person has said you can change just one as long as you replace it with the same horse power (and stroke). Can anyone confirm or deny this?

[FNQCairns]

It's a hard Q but I think you will find the yam 115 has not changed in any real way in all those years so in theory you could purchase good secondhand then use the stuffed one as spare parts for both that are working.

cheers fnq

[Scott nthQld]

is your boat a mono running twins or cat?

If mono, since the other is on its way out have you considered converting to just one big single, like a 225 or 250 even and running trim tabs? Dunno how you'd go doing it though, cos then you'd need all new steering setup, let alone plugging holes from the previous twins.

overall (without factoring any extra work becasue i don't know what would be involved) buying one big single would be initially cheaper than replacing the twins, plus then that means you are only paying to service one rather than 2, fuel economy should remain close, but I think the single should use less.

[pharaoh]

Its a 21' hydrofield. It can be fited with a single but I would like to keep twins, I have had to come home on one engine before and seen mates with singles have to get rescued when it fails. It might only happen once, but thats once to often.

[FNQCairns]

Out of interest the one that you came home on those time/s, is it the one that's stuffed?

cheers fnq

[pharaoh]

Thats a good question. It was probably 6 or 7 years ago and I honestly cant remember anymore. I think it might have been the same one. I remember I couldn't get it started, and later found it was a faulty emergency cut off switch. Nothing to do with whats wrong with the engine now.

[FNQCairns]

Ok it's interesting because often serious engine problems on twin rigs especially can be tracked directly back to even years before when the boat came home on one engine only, the constant lugging killed it or seriously shortened it's life.

I mention this because the safety factor of two identical engines is a bit of misnomer as a result, it might get you home but your wallet will be hanging open all the way. One big engine and a decently sized auxiliary ticks more box's if the boat is to be owned for a while.

cheers fnq

[ozbee]

http://i279.photobucket.com/albums/kk123/ozbee_photos/SANY0375.jpg
a good kicker set up can have more advantages than twins .will set you home at a good sailing speed . also a power source to re charge batteries (pull start as well as electric) with a thrust prop that 20 can push along quite well at half throttle .yes a twin may give you a false sense of security as one wont get you up anyhow unless you have a box of spare props. and can you change one at sea most unlikely so you may not end up much faster than the kicker .

[pharaoh]

Just thought I will update with what I ended up with. I finished up replacing one of the 115's with a new one. I looked into getting a single 200, but with the design of the hydrofield I would either need to add a pod or seriously modify the back above the transom to get the motor to tilt with the added hight of the extra 2 cylinders.

So I now have a 1989 and a 2010 model on the back. They work ok together, sure one throttle is further forward than the other to match revs and I had to play around a little finding where to trim each motor to get them perfect but now I have that sussed out its all good.

[Wet Work]

Hi Pharoah. I would prefer to stay with twins so i think you made the best decision. There is a good argument for a big single with a decent size auxilliary (25-30hp for a boat like yours). Going up a shaft length should have given you the clearance you needed for tilting.

Just a comment on the throttle positions. I would have thought you could adjust the throttle cables a bit too get them in alignment. There is a decent amount of adjustment with yamaha throttle cables and when you have 2 of them you should be able to get them set up really close.