Sealine S28 won't get on the plane

[dkclark001]

I have own my Sealine S28 for the last 12 years. The boat was sea trailed before it was purchased and it popped on the plane first time, every time - with a top speed of over 28 knots. We then moved the boat up to Norfolk and it remained on the Broads for 9 years doing no more than 5-7 mph. The boat was fully serviced in Norfolk every year by a Mercruiser main dealer.

3 years ago we moved the boat back down to Portland and back into the marine environment it deserves to be in, this when our troubles began. The boat will not go up on to the plane and the engines hit a wall at 2500 rpm. For your information, the boat is equipped with the following running gear:- Twin Mercruiser 2.8 D-Tronic 165 bhp diesels, bravo 3 duo props - currently pitch at 24. There has been no changes made to this specification during my ownership, other than brand new props fitted during 2015 from 26's to 24's in an attempt to produce more rev's. Since trying to get the boat back on the plane, we have suffered a lot of black smoke / soot and a lack of power (I have been told black smoke is 'better news' and is a sign of lack of air intake & is over-fuelling).

So far in the last three years the following work has been completed:-

1. Turbo waste gates fully refurbished and bench tested twice
2. Out drives fully serviced 2016
3. Hull scrubbed 5 times and anti fouled 3 times in three years
4. Props changed from 26's to 24's (the original props worked but I was advised to change them to get more revs)
5. Boost pressure checked on both sides of the inter-cooler and the differential appears to be in line with the manufacturers specification
6. Overall boost pressure was lower on starboard engine in comparison to the port engine.
7. Starboard turbo was removed and completely refurbished by a professional company and refitted today. Both engines now boost to a maximum of 12 psi before the engines hit a wall at approximately 2500 rpm, 9-10 knots and black smoke & soot. These sea trials were run with an empty water tank and 50% fuel and 2 adults on board.
8. Injectors removed and bench tested with satisfactory results.

It has now been suggested to change the props again down to 22's. As you can imagine I am very reluctant to spend another £2000 when the original props (26's) worked perfectly well 12 years ago.

I would be grateful for any ideas or further testing suggestions as I / local engineers are running out of ideas.

 

[KAL]

Welcome to the forum, although you might have more luck trying the motorboat section as well.

I presume that
1. The hull is clean, as are the props.
2. You are not carrying a load of water in the bilges, unbeknown to you.
3. Your fuel is clean and water-free.
4. The air intake for the engines is clear
5. The fuel filters and pipes are clean.
6. There isn't some form of engine rev limiter that has kicked in.
7. The engineers have queried the fault codes on the engine management system.

Just some thoughts and ideas. VicS may be along in a bit with other suggestions.

Best of luck with it.

 

[Topcat47]

You would be better posting this on the motor boat forum, however, this is my contribution. I hope it's helpful.

You took a seagoing boat, capable of 30 knots, to a river system with a 10 knot speed limit. For 9 years, you have been pottering about at little more than tick over. This is a common cause of many problems with Diesel engines, which like to be run fairly consistently at the peak of their power curves. I doubt they 've ever reached normal operating temperature.

I suspect there will be a combination of glazed bores, gummed piston rings and carbon build up on the heads and exhaust manifolds. These are the sort of problems best kept at bay by "Italian tune ups" ( a long run at top speed ). To cure these will involve a total strip down.

If you hunt down Vyv Cox of Cox Engineering, his website is an excellent "go to" resource for a wide range of engineering problems. As a retired professional marine engineer, I always look for his posts myself and am proud to say, still learning from his experience. He will also answer personal queeries and may even rock up on this one, if it catches his eye.

 

[macd]

dkclark: this is the link Topcat mentioned: https://coxengineering.sharepoint.com/Pages/Engine.aspx
You'll see various sub-links on the left of the page.

As said, you've much more chance of informed replies on the mobo forum. It's mainly yotties on here.
That said, Topcat's comments about chronic under-use of a diesel engine could well be right in your case.

 

[Murv]

Charge air coolers caked up?

 

[scottie]

If it did the speed before then how much weight have you added

 

[duncan99210]

On smaller yacht engines the symptoms the op describes of engines refusing to rev above 2500 rpm plus black smoke it would be taken as indicating blocked exhaust elbows. No idea if that applies to the sort of engines the OP has but perhaps worth considering, especially after years of slow running?

 

[[164147]]

Clearly not going to be a prop issue if you've had them before. It's an electronic engine - so short of a fuel / breathing issue as described above then any number of factors could be preventing the ECU from allowing the engine to rev past 2500rpm. I would suggest diagnostics to check all sensors with a VM Motori specialist.

 

[gordmac]

Black smoke tends to suggest too much fuel/too little air. Sounds like the engine is overloading when she tries to plane. I would suggest you now have more load or less power, if the hull is clean and you haven't added more weight then probably the latter. Engine down on power or excessive friction somewhere. Given it has been abused for years with slow running it may be coked up and/or bores glazed. were they run at operating temps or cold?
Is the engine breathing ok? check intercooler is clear, check exhaust is clear. Valves and ports may be clogged with carbon. Loading the engine as much as you can (not smoking a lot though) and letting it get hot might help as might de carboning additives, have a look at what some do to clean agr valves on cars.
Check engine compressions. Check injectors.

 

[Malish]

as per others, exhaust elbows would be where I would start

Forgot to ask - will it free rev to >2500 in neutral?

 

[andyb28]

Did you ever sort this?
I have exactly the same problem for the same reason.