260 Sundancer can’t get on plane.

Captain Gary

New Member
Aug 20, 2018
26
Boat Info
1999 260 Sundancer, 7.4 Litre 454 MPI Single Screw Bravo III Stern Drive; Reformed Sailor!
Engines
7.4 MPI 454 Mercruiser; Bravo III Stern Drive
After getting out of winter storage everything on my 1999 260 Sundancer (injected 7.4 MPI with Bravo drive) fired right up and seemed fine just like last year while motoring slowly in the harbor to my slip. When I got out on the big water (finally!) and tried to run it up and get on plane, it didn't have the power. She seems to run fine up to about 1600-1800 RPM (and around 8 knts) but higher than that she just seems to dog with no power and will quietly "pop" occasionally and just not run "right". I can only get her up to about 2800 RPM at full throttle in gear, well below normal, but there's not enough speed/power to get up on plane. She seems to run smooth to 4500 RPM+ in neutral. The Prop spins easily by hand when not in gear and nothing fouling it. I changed the fuel filer and cleaned the air intake filter unit but it didn't help. Any idea on the problem with no power above 1800 RPM when under load?
 
You are not on the Chain of Lakes in IL are you?
 
No we have a place on the Chain O’Lakes in Waupaca Wi, but we also have a 260 Sundancer in the Port Washington Wisconsin Marina on Lake Michigan.
 
Nice.

There is another thread talking about a 260 on the IL Chain. Not complementary on his boating skills.
 
Different guy fortunately.
 
Been boating for 35+ yrs inland and Lk Michigan. Smaller power boats (18’-20’) inland and mainly a sailor on Lk MI until about 2yrs ago, sold the rag bag and went to the Sundancer on the big pond. The Admiral (AKA my wife) is a game boater but never got used to a boat that heels in the wind so I gave in to her and my bad hand joints and made the change. I have a 50 Ton USCG Masters license but I’m not a mechanic so this has me scratching my head.
 
I’m not a engine expert but if get RPMs in neutral but not in gear, I would be looking at your outdrive.
 
I’m not a engine expert but if get RPMs in neutral but not in gear, I would be looking at your outdrive.
Making RPMs in neutral and not under load indicates a lack of power rather than an out drive issue in my mind.
Not an expert, either but I’d be looking at fuel pressures and or plugged injectors.
 
Popping noise could be your valves or springs.
 
Thanks guys. I’m hoping it’s the fuel system and not the outdrive. I thought maybe the subtle little pop I mentioned was from running to lean. I changed the main fuel filter first thing (looks like an oil filter) and cleaned the air intake flame arrestor to, thought that would do it but no dice. Are there other fuel filters anywhere? Added some seafoam to clean the injectors yesterday and idled in the slip for a while but didn’t have time to take her out and see if that helps. Been thinking a lot about it and I had planned to repaint the bottom with biocide bottom paint this winter but didn’t get to it and then had to rush to get it out of storage this spring because the place was going out of business. It needed painting when I bought it last fall. I can’t see much under there without going in the 50° water but I’m wondering if anybody knows if some algae growth (no barnacles here) on the hull could cause enough drag to cause this?
 
Not saying this is your issue, but this sounds eerily similar to what happened to me on our first boat (Bayliner 245 w/Mercruiser 5.0). The lack of power, inability to get on plane, and the *popping*. Engine would putter sporadically at certain rpm’s. No issue in neutral. Engine could not get up on plane with anyone aboard. It ended up being bad valves on 7 and 8. Valves were embedded and jammed up into the heads. Had to do a complete upper engine rebuild, new heads both sides. It was a festering problem that got progressively worse. Being new to boating at the time, I kept re-propping thinking the prop was bad. Changed fuel filters, symphoned gas and replaced with fresh, nothing worked. I also cleaned and repainted the bottom. I sincerely hope this isn’t your issue but you mentioned the popping. Thats was the giveaway for my mechanic. As soon as he heard the engine do that during a sea trial, he knew it was the valves.
 
Valves or compression. Check your compression and get back to us.
 
Agreed,
I’m a technician, seen worn cam lobes, burnt valves, broken springs , bent pushrods, rocker studs come out or break , siezed lifter , blown head gasket between cylinders etc.. all can cause popping noise only on acceleration
 

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