Question on 342 performance

buggyjdav

Looking for feedback. We have an 04 342 with the Merc. 350 Horizon engines. When it was surveyed the mechanic did compression tests and stood in the engine compartment taking temp readings off the engines while we ran full out. He said the engines were in amazing shape, said he could tell they were never abused, clean just excellent. I swear that we reached 40 MPH on the sea trial with 6 people on board, 1/4 tanks of fuel, holding tank was fairly empty as was fresh water tank. 

I ran the boat the other day with 6 people on board in pretty choppy ocean and struggled to get to 25 MPH at WOT. Now that we have had the boat for over a month we have loaded a lot of gear on, fuel tanks were at 3/4 full, fresh water was full so a lot of additional weight on this run vs. the sea trial. 

My question is does the performance sound normal?

MarkB

Sounds like you did not come off plane.  In choppy conditions it is very difficult to do that.  There is a huge performance difference between displacement cruising (when the whole boat is dragging in the water) and planning (when the boat is pretty much skipping on top of the water). 

Did you have your trim tabs all the way down before you rev'd the engine? This helps get you onto plane, especially with lots of gear and people on board. If there's too much weight at the bag, your stern is loaded and you are going to have difficulty getting it out of the water. Think about distributing some of that weight to the front of the boat (in the compartments in front) - so switch you towels to the back, and heavy stuff to the front.

Also, do not run the engine at WOT for extended periods of time, you will hurt that engine. You will also burn a lot of oil if you do that. Short spurts to WOT are okay, but for general use, try and stick to 80% of WOT, which should be around 4000 RPM.

buggyjdav

Thanks MarkB. The trim tabs were down but only after I wad having trouble getting on plane. I only ran WOT to test performance, I usually try to run very conservatively. 

MarkB

So what about your weight distribution? Did you have everyone sitting at the back? How heavy? Where's your heavy gear positioned?

MarkB

And remember your gas tank full is probably 600 to 700 lbs.  That's a big difference. Water tank is probably another 100 - 120 lbs full.

raybo3

Were your outdrives all the way down??? Is the bottom clean? 

TonyWalker

My experience with the Volvo 280's when I had them was much better than what you are describing.  I never had a load situation that did not allow me to get up on plane.  I am thinking that there must be a cause for this lack of performance..

Tony
Salt Shaker 342

TonyWalker

You might want to investigate your props to see that you have ones with the correct ptich.

MarkB

Tony, issue is he got the performance during the sea trial. Unless they changed the props on him, it either has to do with weight, maintenance or operating procedure.

Black_Diamond

An rpm check at WOT, trimmed out and on plane will help if you have the correct prop pitch. Running B-3 drives?  

TonyWalker

MarkB, I reread the original post.  You are correct, not likely incorrect props.

LaRea

In flat water, you should still get close to 40 mph even with fuel and load.  Next time out, take a look at your wake and make sure it looks normal (symmetrical port-to-stbd, and no big rooster-tail).  

Maybe you have something fouling one of your drives, like a stick or rope.

summerx

is the bottom clean?  if it has been sitting in salt water for the last 4-6 weeks and has a lot of growth, it can really affect the performance. 

Stodge

I normally run about 3600-3700 RPM and get to 28-30 MPH depending on lake conditions.  One of these days I need to see what I get at WOT.