No Accelleration

[stownsend]

I’m after a bit of help…

Some history, I had a VP 260 (AQ151 with 290 SP-A leg) in a 16 ft speed boat. Took this engine and installed it into a 23 ft cabin cruiser (Invader 2200).

I serviced / overhauled the engine, new head gasket; seals etc… spark plugs and leads, coil, alternator, etc, cleaned and rebuilt the crabs (twin solex) I replaced the timing belt, checked and rechecked the timing several times (all the notices line up as per the VP workshop manuals and Solec manual), she idles fine but under load I can’t get anymore than 1500 to 2000 rpm. If I rev her out of gear she revs fine, any ideas?

Could my timing be out by a couple of tooth on the top pulley, and she is just off when the valves open?

Fuel starvation / carbs issue?

Prop ?

Any help will be much appreciated as I’m going round in circles!

Cheers

Stu

 

[Wiggo]

Is it the original prop? If so, it's likely to be wrong for the bigger boat (and a 23 footer with only 150hp sounds marginal). Not sure that it would drag the revs that low, though...

 

[omega2]

Prop too big? maybe fine for a lightweight boat but now trying to shift heavier load.

 

[stownsend]

I'm planning to remove the prop and give it a try, should rev fine.

Cheers

Stu

 

[Wiggo]

If you tell us teh prop size, someone hereabouts will be able to advise if it's the right size or not...

 

[duncan]

gearing will be all wrong

combination of outdrive gear ratio and prop pitch

as others have suggested - change the props

the key issue you have to resolve is getting the engine power band matched to the new boats displacement hull speed and 'hump'

 

[stownsend]

thanks for the info, i'm doing the testing when tied up on the pontoon, would that have any impact ?

 

[omega2]

thanks for the info, i'm doing the testing when tied up on the pontoon, would that have any impact ?

do you mean wot in gear whilst tied to berth?? if so YES IT WILL.

 

[jax]

Think I would investigate for a fuel starvation problem before swaping prop esp as you say the engine revs OK with no load

 

[stownsend]

Fuel does seam to be flying into the carbs OK, could it be running too rich / lean, i'll check the plugs to see if they are damp when I down there next after I've run her a bit and tweak the carbs.

Would being tied up to the pontoon and wrong prop, reduce the RPM by that much ?

Cheers

Stu

 

[lovezoo]

As others have said, if you are using the prop from a 16' boat on a 23' boat it will almost certainly be the wrong size.

I also wouldn't recommend trying to get max revs in or out of gear whilst tied up - the engine and leg aren't designed to do that.

 

[volvopaul]

You cannot possibly test the set up that way, as said the prop or props will be far too big in size, to give you an idea a fairline sprint 21ft with a v8 5 litre petrol has 1.93 to 1 ratio drive and b4 duo props, id say that you will get on the plane with 150hp when its propped right but it wont be a speed boat with 150hp, another example is a fairline sport fury with 2x aq151s on single prop drives will give top 20s knots flat out.

 

[omega2]

prop size

this now sounds like a job for Paul Williams, www.clementsmarine.co.uk have the relevant info ready for him i.e. horse power, gear ratio, weight of boat, length at water line. He will give the low down.