1998 Twin 4.3 Mercruiser's Will not plane out!! Seems to have no power at WOT. Please Help!

Hello,

I am hoping someone can help with a problem that I having. I have twin 4.3L Mercruiser's engines with Alpha One GEN two outdrives. Engines have double barrel carbs, thunderbolt ignition. My problem is that I have no power when both engines are at WOT. The boat stands straight up, barely moving and never planes out. Both RPM gauges are reading around 4000 at WOT. Both outdrives and trim tabs are fully down as well. I changed the fuel/water separator filters as well as checked the inlet filters going into the carbs but did not see any sediment restricting fuel. Also no water could be seen in the filters. I am hoping this has happened to someone and could get some advise before getting compressions taken and digging deep into the engines. Pretty sure the props are not slipping as my RMP's are not going past 4000. Growth on the hull shouldn't be an issue either as I use the boat a few times a week. Any help would be greatly appreciated!

Thank you,

CW

unless your longer than 26 feet the twin 4.3`s should have ample power to plane Anything longer should have 5.7`s or 6.1`s
You would be surprised how fast a hull can foul. grab a set of goggles and take a look.

Bt Doctur said:

unless your longer than 26 feet the twin 4.3`s should have ample power to plane Anything longer should have 5.7`s or 6.1`s
You would be surprised how fast a hull can foul. grab a set of goggles and take a look.

Click to expand...

It's a 29ft (32ft overall) SeaRay Sundancer.

How long you own this boat?... always been like this?

Your craft sounds like a dealer special,Underpowered,thread#2 said it first

Is it possible the hull is waterlogged with a leaky double bottom or ??

Jeff

4.3ltrs will plane out a 290 Sundancer with no problem. Yes it is under powered. I had a 1989 280 Sundancer with 4.3 with Q-Jets that had a vacuflush system and a Kohler 5kw Gen set. It also had 300lbs of sand bags under the front v birth to lift the transom while docked and it would plane off in 3-4 seconds.

How long have you owned this boat?

How much unneeded crap do you have in the cabin?

Driving a boat regularly does not prevent growth.

Was any repair work done to the boat recently?

This is my 3rd season with this boat. I've always thoughtfrom day one that this boat is underpowered. Also I've always thought it tooklonger than normal to get on plane. Only this summer it's refusing to planeout. We don't really have much stuff in the cabin and I would thing by puttingmore weight in the in cabin, mainly under the V-birth would help the front ofthe boat go down when trying to get on plane. I actually thought of puttingsome type stationary weight light sand bags in V-birth.

As far as the growth on the bottom, I understand that operatingthe boat doesn't prevent build up. But what I mean is that the boat does notsit for long periods of time allowing abnormal growth build up. At the most itsits for 2-3 days without being used. Every year since I owned the boat I havebeen present when the boat is hauled out of the water for winter storage andeach year the growth on the bottom of the boat is very minimal. Believe me Iknow what's on there now isn't helping my issue but I am willing to bet it'salso not the main cause.

As far as repairs.... I've performed all the normalmaintenance on the boat. Oil changes, fuel filters etc.. Since purchase theboat three seasons ago I have not had a full tune up. Previous owner providedinvoice from having the plugs and wire's checked. Each year my marina checksthe gap on the plugs but have yet to tell me I need to replace anything. So Iam unclear when the last time both engines had plugs, cap, rotor changed. Maybethat's the issue? Also last summer one engine would stall in reverse. I checkthrottle cable adjustment, all my linkages but everything seemed ok. Readsomewhere that someone else was having that same issue and he had a gummed upcarb. So I purchased a carb rebuild kit and it fixed my problem and it workedjust fine. Still was a pain to get on plane but fixed the engine stalling. Sothat's where I am at right now. I have all the parts to do the tune up. I willprobably do it this weekend. Any thoughts?

FWIW... my experience is that I never get 3 good seasons on a disti cap/rotor on a T'bolt V system with a boat in NJ sitting in seawater for 5 to 6 months at a time and then winter stored 50 yards from the bay. Re: "paying a yard to check the gap on plugs...." mmm... I've owned and maintained boats since 1964 ( always in seawater) and NEVER did that, either myself or paid someone to do it. Given the trouble (read labor cost! @ today's rates) to do this ( unless you have an inline 4) vs the cost of plugs, if the plugs come out, they get replaced... which I do every 3rd or 4th season IF engine runs OK, sooner if not. I just replaced a set of OEM wires after 9 seasons and they were apparently still OK. If you don't know when the parts were replaced (cap/rotor) I'd replace them.

Bottom growth: hull pressure washed IMMEDIATELY (bottom still damp!) on haulout every season. Since I've been using a multiseason (water based) ablative, I just repaint the bad spots every season, and the whole bottom every third or fourth season depending on results @ haulout. Its not just the barnacles that are an issue, its slime as well.

Always start with a tuneup,then troubleshoot from there,good luck

Give it a tune up with Quick sliver parts. If the dist pick ups are Two wire (No ground) replace them.