Seward 25 prop size

[john m]

I have a seaward 25 with twin Yanmar 4jh2ute the hull and props are clean and clear but I can only achieve 12 kts and get black smoke I’m thinking it’s overproped is there anyone on here could tell me the size of prop they have and what speed I should be getting

 

[AllanG]

Sorry I can’t help with an answer, but I’m sure if you contacted Seaward directly, they should be able to advise.

 

[Bod]

Unfortunately Seaward went into liquidation last year, so wont be able to help. I have the 110hp Yanmars on a 25 and can reach 21 knots with clean bottom and props (3100rpm).
I’d be surprised if the props have been changed from factory supplied size - so should be matched.
What rpm can you reach? - I’ve found the turbos are susceptible to coking up - may be worth checking out.

 

[Alicatt]

The 4JH2UTE is 46hp?
the 4JH3-te is around 125hp and fitted to the Seward 25 which should give 21knots

 

[Montemar]

I have just seen specced as 100hp on Mrs Google

 

[Boathook]

I have just seen specced as 100hp on Mrs Google

Found this
http://marx-ftp.de/Downloads/Marine/Innenborder/Datasheet_old/Datasheet_4JH2-UTE_englisch.pdf

100hp and 3600rpm. The OP really needs to give the maximum rpm that they are achieving.

 

[john m]

Thanks for the reply’s I can only get 2600 rpm and then the black smoke starts the hull is clean and no fouling anywhere

 

[Bod]

Is this something that has just started, or is this a new to you boat?
If the former I’ll bang the turbo problem drum again - the turbos kick in at ~2400. Even if only one is malfunctioning, it seems to prevent the boat accelerating enough to let the other engine ‘spool up’.
Do the engines rev freely put of gear?
Re. Prop pitch - as a rough check you should find 800rpm gives you about 4.5 kn, 1200 about 6.5 kn. and 2000 about 10 kn. (Seaward 25 with yanmar 110’s so similar configuration).

 

[john m]

Is this something that has just started, or is this a new to you boat?
If the former I’ll bang the turbo problem drum again - the turbos kick in at ~2400. Even if only one is malfunctioning, it seems to prevent the boat accelerating enough to let the other engine ‘spool up’.
Do the engines rev freely put of gear?
Re. Prop pitch - as a rough check you should find 800rpm gives you about 4.5 kn, 1200 about 6.5 kn. and 2000 about 10 kn. (Seaward 25 with yanmar 110’s so similar configuration).

Yes it’s a new to me boat I replaced one engine with a good used one your calculation for the speed ar roughly what we’re getting

 

[scottie]

was the replacement unit bobtail!

 

[Tranona]

It is unlikely that the props are the wrong size if it has been on the boat all the time so sounds more like the turbo(s) are not giving full boost. The other possibility hinted at in 10 is that the replacement engine might have a different ratio gearbox.