WOT 24-26mph @4000rpm

[hausherrs]

I have 1996 400 with the 454XLi. They run well, no known problems.

I wanted to bounce a couple things off of the list.

1) WOT is 4000 RPM and 24mph or 27mph depending on the current and winds. This seems a little slower than it should for 4k rpm. I dont cruse at that speed but if I take it out for an hour, and its smooth out I like to run it up for a few minutes. Also seems like its struggling to get on a plane. I want to say crusing @ 3400 I hang around 20mph maybe 18 into the wind

2) I have a closed engine cooling system with heat exchangers. Temps run about 180 degrees, which I hear is normal. When I do these spirited runs it stays around that level but then the temp climbs about 10+ degrees when I idle it down. The stb can get close to 200. Is this what others are seeing?

Thoughts??

Thanks

Steven

[Viper]

Check the bottom of the hull. If it's fouled, it'll slow you down.

Closed cooling should run at 160. 180 is pushing it IMO and 200 is an indication that there is a raw water cooling problem such as insufficient volume, or a flow restriction, bad impellers, etc. There are several things that will cause this but they basically boil down to volume and flow. You may also have a problem with the closed cooled circuit such as low coolant, bad t-stat, heat exchanger issue, etc. The first thing I would do is actually confirm at the engines that they are indeed running this hot. You can do this with an IR temp gun pointed at the temp sender. Everyone should have one of these on board. It won't be exact but it'll give you a pretty good indication if there is indeed a cooling issue or if it's simply a sender or gage issue.

[AaHubb]

The only way my 404 would get to 24mph is down hill with a tail wind. I mostly run at hull speed ~1200 to 1400 rpm.
..Aaron

[bud37]

Source of the post The only way my 404 would get to 24mph is down hill with a tail wind. I mostly run at hull speed ~1200 to 1400 rpm.
..Aaron

Was thinking the same thing.. that is a big heavy boat.....

[hausherrs]

Check the bottom of the hull. If it's fouled, it'll slow you down.

I paid a guy to scrub the bottom 2 months ago. I am going to take my bore scope out there so I can see what it looks like without getting wet.

Closed cooling should run at 160. 180 is pushing it IMO and 200 is an indication that there is a raw water cooling problem such as insufficient volume, or a flow restriction, bad impellers, etc. There are several things that will cause this but they basically boil down to volume and flow. You may also have a problem with the closed cooled circuit such as low coolant, bad t-stat, heat exchanger issue, etc. The first thing I would do is actually confirm at the engines that they are indeed running this hot. You can do this with an IR temp gun pointed at the temp sender. Everyone should have one of these on board. It won't be exact but it'll give you a pretty good indication if there is indeed a cooling issue or if it's simply a sender or gage issue.

I will start with the strainers then impellers. I got a quote to get the heat exchangers cleaned but he wanted over $900 in labor. Ill figure out how to do it myself for that much. He said he flushes them with muratic acid. Is this the best way?

Thanks for the input.

Steven

[hausherrs]

The only way my 404 would get to 24mph is down hill with a tail wind. I mostly run at hull speed ~1200 to 1400 rpm.
..Aaron

I do too. When the broker met with me on the boat he was raving about how it tops out at about 29. I dont care to go that fast. When I took her out to stretch her legs I couldnt get over 27 with the wind and current. What would you say plaining speed would be?

[g36]

my 1997 405 is according to specs about 6000 lbs more than your 400. i have the same engines 454xli. i max out on my tachs at 4400 i think you should be able to reach this or closer . i dont run mine like this either but on occasion i still want to see if it will reach this. if i had a diesel i would think they should push it even better. i know these are not speed boats but it does seem like you arent running well if its struggles to get on plane. trim tabs fully working? all 3 fuel filters clean or replaced?

[hausherrs]

my 1997 405 is according to specs about 6000 lbs more than your 400. i have the same engines 454xli. i max out on my tachs at 4400 i think you should be able to reach this or closer . i dont run mine like this either but on occasion i still want to see if it will reach this. if i had a diesel i would think they should push it even better. i know these are not speed boats but it does seem like you arent running well if its struggles to get on plane. trim tabs fully working? all 3 fuel filters clean or replaced?

I bought the boat about 3 months ago. I have a list of maintenance things that I want to do so I have a baseline. Fuel filters are on the list. I also plan to do an oil analysis when I do my first oil change this winter.

I would like to have the filters before tearing it apart. Do you happen to have a parts list with numbers for the three filters? One is just a screen I believe. So only 2 are replaceable?

[g36]

Yes the oberg ufo you can open and clean it and reuse
The water seperator I have uses this
http://www.defender.com/product.jsp?pat ... &id=133957
The other is and of course the are choices on this bUT anyway
https://www.marinepartssource.com/newde ... fgno=23250

I just shop the Internet for the best prices I just referenced this links for info for you

[hausherrs]

Source of the post Yes the oberg ufo you can open and clean it and reuse
The water seperator I have uses this
http://www.defender.com/product.jsp?pat ... &id=133957
The other is and of course the are choices on this bUT anyway
https://www.marinepartssource.com/newde ... fgno=23250

I just shop the Internet for the best prices I just referenced this links for info for you

Ordered! Thanks for the info!