PAC 22 acceleration problem

clumberboy · 21 November 2015, 12:32

Hi everyone,

hope somebody can point me in the right direction as im stumped at the moment,
My boss just bought a pac22 sight unseen and not tested, apparently it has only done 1000hrs from new,
The boat accelerates very slowly up to 1700rpm with a bit of black smoke and as soon as it gets up to this speed just suddenly accelerates away, the turbo was quite sticky and loads of play in the shaft, fitted brand new turbo and it has the same problem.
The engine is a 4lha stp, with borg warmer 72 gearbox and a 100 series sterndrive, no info came with this boat so unsure of gearset or prop

beamishken · 21 November 2015, 12:45

Those yanmars are quite prone to turbo lag.
First thing is the hull clean?
What rpm is the engine making at wot I think they should make just over 3400 with a clean hull
If it doesn't then it's possibly over propped or dirty
The intercooler can coke up on both the air & water side which reduces power too
Also is the exhaust system free from obstructions
Need more info to narrow down the possible causes

Pete7 · 21 November 2015, 22:27

That sounds about right for P22 with a standard 160hp engine. Should manage about 26 knots flat out at about 2600 revs. Make sure the weight is kept forward (people) if it struggles to get on the plane but it does take time compared to an outboard rib.

I added a set of foils to the rear chines which helped provide lift to the stern.

Lots of posts on here about Pacific 22s, worth doing a search back over 12 years.

Worth a read:

http://www.northernexposurerescue.or...s/Pac%2022.pdf

Searider · 21 November 2015, 22:31

Isn't the 4lha stp the 240hp one?

What rpm and boat speed are you getting?

Pete7 · 21 November 2015, 22:37

Quote:

Originally Posted by Searider

Isn't the 4lha stp the 240hp one?

What rpm and boat speed are you getting?

Ah good point, what is the number on the boat plate 8110 would be the 10th boat in 1981 so should give you an idea of its age.

beamishken · 21 November 2015, 22:54

[QUOTE=Pete7;700360]That sounds about right for P22 with a standard 160hp engine. Should manage about 26 knots flat out at about 2600 revs. Quote

I assume you mean 3600rpm?
Won't last very long if it's only making 2600rpm at wot!

Pete7 · 21 November 2015, 23:14

[QUOTE=beamishken;700366]

Quote:

Originally Posted by Pete7

That sounds about right for P22 with a standard 160hp engine. Should manage about 26 knots flat out at about 2600 revs. Quote

I assume you mean 3600rpm?
Won't last very long if it's only making 2600rpm at wot!

I posted that before Sea Rider pointed out it has a Yanmar in it. The quote was for the older Ford Dover 4.2 engine.

Pete

beamishken · 21 November 2015, 23:40

[QUOTE=Pete7;700370]

Quote:

Originally Posted by beamishken

I posted that before Sea Rider pointed out it has a Yanmar in it. The quote was for the older Ford Dover 4.2 engine.

Pete

Says in his first post it's a 4lh stp

Pete7 · 21 November 2015, 23:44

[QUOTE=beamishken;700372]

Quote:

Originally Posted by Pete7

Says in his first post it's a 4lh stp

Which I overlooked because he also mentioned the Borg Warner 72 box and stern drive 100. Would be interesting matching the Yanmar to the Borg Warner, wonder why they didn't use a Yanmar box and alter the jack shaft if the engine position is slightly different, still lets see what his answers to this thread are.

Pete

beamishken · 22 November 2015, 00:09

Isn't that a standard set up in the later pac's? The yanmar usually comes with a zf/ hurth box but the military spec some strange stuff or possibly buy the engines bobtail & fit the origional box during re powers

Pete7 · 22 November 2015, 00:19

Quote:

Originally Posted by beamishken

Isn't that a standard set up in the later pac's? The yanmar usually comes with a zf/ hurth box but the military spec some strange stuff or possibly buy the engines bobtail & fit the origional box during re powers

The early P22s had a Mermaid turbo Four with BW 72 box and sternpower 101 leg. The Mk2 has jets. In between well when you walked around Halmatic when they were building boats there was always a series of odd looking development ribs which you weren't allowed to photo graph, even for those of us serving at the time.

M.Thornton · 22 November 2015, 08:52

Try dropping your trim- tabs half way to lift your stern when you set off

clumberboy · 26 November 2015, 22:40

hi
everyone, the hull is immaculate, once turbo finally kicks in it quite happily tears away to 3400, was tracked doing 34 knots plus, these ribs are all ex military and the gearboxes and sterndrives are what they came with, the engines were a later addition when swapped from the 24v model yanmars. Exhaust system is clean, not sure when intercoolers were last cleaned as i have no history at all on this boat, just after a few pointers on what to try next, about to put another sterndrive on as suspect could be wrong gearset, not a new one the boss bought a spare one at the same time.

beamishken · 27 November 2015, 07:56

3400 is the max rpm for the engine so your not too far away on overall final drive ratio.it should be propped to about 3550 max (but never ran at over 3400) & the standard tach is notorious for over reading so you may be slightly over propped or possibly a little down on power overall.
Personally my next step would be strip intercooler and clean air and water sides then try again & double check rpm with a shop tach. Also worth doing a high idle test to check governor setting. It's no good trying to increase max rpm if it's governed to 3400
Obviously if you have a lower ratio drive to swap over then that gives the same result as reducing prop pitch