Wet foam

[Cphil]

So I have an X70 that I did some layout mods to. I made a hole in the floor and ran an auger style bit through my foam by hand to make a hole for a cooler drain tube. When doing this my bit came back out pretty wet. Dried it off. Ran it up and down again. Still wet...and on and on. Do you guys think this is a pretty good indication that most likely all my foam under my floor panel is soaked?? Another thing is I should run 5500 RPM, (WOT) and probably 55-58 with my set up and average load. I can barely get 5100 at 52 MPH on a great running 150 Vmax.
I believe I’m slowed down by heavy wet foam? Any opinions?

[mittenbass]

Yes, sounds like it’s water logged. It’s a known problem on these older xpress models if they were left outside a lot uncovered and/or with the drain plug in. I have an X70 with a 150 Yamaha and run 59mph loaded and 62mph light. Setup and prop can make a big difference though so just because your speed is off doesn’t necessarily mean the foam is wet, but it sounds like it is in your case. Dents on the bottom of the hull, particularly at the back of the pad can slow you down too.

[alli ss]

Do the new ones have foam in the floor? Thats a pretty dumb idea.

[T-Bob]

Do the new ones have foam in the floor? Thats a pretty dumb idea.

Yes they do. They claim its a closed cell foam and does not absorb water but I would beg to differ if its left out in the rain for long periods of time.

[alli ss]

Thats some dumb chit. They should at least provide access to the foamed areas for observation. That closed cell foam absorbs water just like its cheap cousin. The foam chunks i have found in my new xpress is no different than the old foam they put in boats in the 70’s

[Cphil]

Yes, sounds like it’s water logged. It’s a known problem on these older xpress models if they were left outside a lot uncovered and/or with the drain plug in. I have an X70 with a 150 Yamaha and run 59mph loaded and 62mph light. Setup and prop can make a big difference though so just because your speed is off doesn’t necessarily mean the foam is wet, but it sounds like it is in your case. Dents on the bottom of the hull, particularly at the back of the pad can slow you down too.

Im running 3 3/4” prop to pad and I’ve tried 4 different props with very little success. Three 3 blade props in 23, 24, and 25 pitch and one 4 blade 23P. Best all around in RPM and speed has been the 24 Tempest on there now. What’s weird is my (WOT) RPM is the same wether it’s a 23 or even a 25. My motor checks out great so that is why I think the extra weight is only letting the motor spin to lower RPMs and slowing the boat down.
Thanks for replies

[Cphil]

Also, smooth dent free hull too. Nothing there to worry about.
Thanks

[Arkyarcher]

A 22 four blade or 21 three blade should spin up past 5200 if not, you aren't getting full throttle. IMHO

[Cphil]

I’ve gone over those normal checks. Plus when I drop in pitch I do really start to loose top end speed. I can’t have that. It’s a carbed motor so when I open the throttle completely with the control it does open the throttle blades completely on all 6. Unless the timing advance is wrong. I don’t know. It’s weird. Besides this lack of speed issue it does run flawlessly. Fires on all cylinders has perfect compression and so on

[Arkyarcher]

In theory losing one inch per revolution but gaining 600 revolutions per minute should have a higher top end. Of course that's in theory and your results may prove it wrong.