my 300 vmax hdpi can't plane my boat....

last yr, i pour some seafoam into my tanks, to take it out for one last outing to get the seafoam thru the lines. got to the lake n the boat won't plane. can't get any higher than 3.4k rpm. had someone sit up front, got her to plain but took 25 secs to plane. even then on plane will not go over 3.4k rpm. so i said f.. it n stored it for the winter. assuming it was the sefoam. spring comes along, i refuel with more fuel, took her out to the lake n same result. don't know what's wrong, am stumped. haven't changed plugs yet, could it be the plugs, blown cylinder, ???.

Just curious, but when you seafoamed it, what concentration (ie, a can in how many gallons)? I don't think it's a blown cylinder as you would probably notice it running very rough & vibrating at 3400.

A few thoughts related to the seafoam.

1) A very heavy concentration of seafoam will tend to bog down engines. Just because you put fresh fuel in the tank after letting it sit, you still need to purge the old seafoamed fuel out of the lines between the tank and the cylinders (assuming that the mix is part of the problem). Did it run long enought to do this?

2) Pull the plugs and see if they are gunked up. Like you said, it can happen. If you have a compression gauge, test the cylinders since you are pulling plugs anyway. Double check the manual for your year 300 HPDI as most of the HPDI's do not have the same compression ratio for all cyclinders. Most have 2 with a slightly different ratio.

3) How old a boat is it and what is the fuel tank made of? One of the issues folks in salt water boats with alluminum tanks saw a lot of when ethonol first came out was it actually worked as a solvent and loosened up crud in their tanks and in the fuel lines clogging filters and in extreme cases the fuel lines in the boat. A related complaint I've seen a lot of posts on is after the first switch to e10 fuel in an boat with an alluminum tank, there is a whitish deposit that clogs the VST filter in the HPDI's. Seems to be related to the alluminum tank it's self and looks like some real fine oxidation residue. From what I've read it will get by a 10 micron Racor which is what most boats have. Seafoam is also a solvent and may have contributed to this as well. Sounds like it could be a classic VST filter issue if it's starving for fuel on top end.

4) crappy fuel in the tank to start with (ie, water & ethonol?).

Here is what I would start with. Pull the VST tank and inspect, clean and/or change the filter. A HPDI needs this done regularly anyway. I suspect that you will find it will be mostly clogged. Once it's good to go, inspect the plugs and change as necessary. I would then take a 3 or 6 gallon portable tank of brand new fuel and plumb it straight into the engine fuel line. That way you have eliminated the internal boat tank and the old fuel. Another plus of using the portable tank is if it clears up you know it's in the on board tank, the on board fuel, or the on board fuel lines or on board filter. If it still runs at 3400 max then you know its somewhere in the engine. If it is still giving you problems after running enough to get the fresh fuel circulated, then you can move on to other suspects (and it involves more filters for starters - I swear they went filter crazy in designing those HPDI's).

I'm sure others will chime in shortly, but that's my initial 2 cents worth

the seafoam ratio was 1 gallon of seafoam vs 8 gallons of gas. i assumed it was the seafoam concentration, so i waited till spring n filled another 10 gallons of gas to help dilute the seafoam. but it didn't change the result. i even idled around for 15-20 mins, same outcome.

if it doesn't rain tomorrow, i'll go change the plugs then take her out to the lake to see if it's the seafoam/gas issue. it couldn't hold idle for long the day i pour the seafoam in but it idled fine this spring when i took her out since filling more gas. plus i gotta fix that leaking water hose on the motor anyways.

Change the metal fuel filter on the motor. Mine lost top end would not go past 5000 Rpms..... Brace yourself that filter is around 100 bucks!!

That would be the metal filter in the fuel line coming out of the VST canister. That was going to be next on my list. And if it's clogged, you can bet the VST filter is gunked up also as it is upstream in the flow.

I just ordered one of those cannister filters for my 200HPDI and I think it was $117. I would change it every 3 years "no matter what".

found my prob. i'm still in aw that my motor didn'tt seize. found out i had a major leak on the front side of gasket part number 6D0-15462-00-00 spraying water a urine size stream straight forward into the air intake. my motor ingest the water into the bottom 3 cylinder. this caused the plug to wet n not fire. no wonder my boat can plain. Phew!!!!!!

WOW! I've never heard of that before. Glad you found the problem because nobody would have guessed it.

My dads 300 hpdi did the exact same thing twice. They said he wasn't draining the water out before storing it in winter.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ricqik &raquo;</TD></TR><TR><TD CLASS="quote">my motor ingest the water into the bottom 3 cylinder.</TD></TR></TABLE>

Just what do you mean by bottom 3 cylinders? You have 2 at the bottom 2 in the middle and 2 on top. http://www.bassboatcentral.com/smileys/Laugh.gif

i'm looking at it from the throttle intake side. http://www.bassboatcentral.com/smileys/wink.gif

http://www.bassboatcentral.com/smileys/eek.gif

Nice looking deer! Would love to find one like that!!!!