sealine 22 very slow

[jwilky]

Can anyone out there help.I have recently fitted a recon motor to a 22 foot sealine cruiser.the boat is about 12 yrs old and fitted with a 3.9 v6 GM petrol engine.It weighs about 2 tons. The performance is very disapointing.It will do six knotts at 1500 rpm and only 10 a t3500rpm .It won't rev above this under load .The carb has been cleaned new fuel added the lift pump has a good constant delivery.The carb is opening fully Iv'e tried altering the trim tabs etc bit nothing seems to help.I dont know how it should perform as Ive only been used to sail boats and it was out of commision when purchase the previous owner has passed on.

 

[duncan]

it sounds like a prop or gearing issue.

the boat should get up and go with about 160hp or so - does the 3.9 deliver enough? Would have thought so as the 4.3 provides around 210 - 220

 

[spannerman]

When you say a recon motor, was it originally a marine motor or a marinised car engine, if so it could have the wrong type of cam for marine use. If the prop and gearing is correct have you checked the ignition timing, it could even be the cam timing is out, I have come across several motors that were timed up wrong but still ran although were down on power. It should wind up to 4400-4800rpm.

 

[JKay]

what revs with no load?

cheers Joe