20' Almar with Hamilton 773 Jet Drive won't plane with a load

[mrtoybox]

First the Secs. 1990 Almar with 350HP 350 Chev carbureted with a Pozi nozzle installed at 92mm diameter. A couple of months ago I took out all the flotation foam because it was holding 500 lbs of water. For real i weighed teh foam when I had it all out. I replaced it with Marine grade 2 part pourable foam. The boat ran fantastic, like a new boat. It handled 6 divers with tanks and all the gear and got on plane just fine. I added the Pozi nozzle and all was still well the boat ran great even under load.

Now it seems like suddenly it won't get up on plane with 4 divers and gear. I've lost about 250-300 RPM at WOT even when the boat is empty. It acts like it's full of water again so i pulled up part of the floor and their is now water in the foam that I can see. Once the boat finally and I mean it takes 1to 2 to 3 minutes, to get on plane it has to run at almoss WOT to keep it on plane. By the way WOT was 4500 RPM now it's down to 4200 to 4250.

i disconnected the drive shaft and the Jet turns easily by hand. One thing I noticed is the motor seems to be really working hard. Steam just boils out of the back end and it didn't used to do that.

This could be coincidental, but it is part os the story. This slow down in performance seems to coincide with an oil change. Yep, I went from 10W40 to 5W30 because when I would slow down from planing speed the engine adcted like it had a valve or lifter slightly out of adjustment and would tap,tap,tap. I also had an oil additive in the oil, a good quality, Lucas Heavy Duty Oil Stabilizer, that I haven't put in this oil change to see if that was causing the tapping. With only the 5W30 in the engine their has been no tapping after running hard.

Any suggestions?

 

[Bondo]

Re: 20' Almar with Hamilton 773 Jet Drive won't plane with a load

Ayuh,... It sounds like your motor is Sick,...
Give it a Diagnostic Tune Up,...

 

[NYBo]

Re: 20' Almar with Hamilton 773 Jet Drive won't plane with a load

How did the new foam get so wet? Sounds like you've got a leak and are again hauling around water.

From the rest of the post, I think he made a typo:

It acts like it's full of water again so i pulled up part of the floor and their is now water in the foam that I can see.

I think he meant to type "is no water in the foam that I can see."

I agree with Bond-o. Time to check the basics - spark, compression, etc.

 

[81 beachcomber]

Re: 20' Almar with Hamilton 773 Jet Drive won't plane with a load

ya i agree, maybe just a carb tune...my 350 in my car acted similarly when the carb was out, no power at all and pinned took forever to get up to redline. check all the basics, carb tune, defeinetly check your timing, spark, compression etc etc... good luck and let us know

 

[mrtoybox]

Re: 20' Almar with Hamilton 773 Jet Drive won't plane with a load

Sorry for the Typos. I cannot see any water in the new foam, However it does get wet because we climb into the boat with our dive gear on when we complete a dive and the plywood floor does not seal the foam from getting wet.

I talked with Randy at KEM in Oregon, about the issue and he doesn't think it's a problem with the jet either. He says most jet problems create over revving. He was surprised when I told him the motor was puling 4300 rpm's and the boat still would not plane. I am carrying an extra 1600 lbs when loaded with divers but it worked before.

That's what bugs me. It's only running about 250 rpms less but it won't put the boat on plane. Steam just boils out of the exhaust but does not smell like antifreeze.

Thanks for the advise. I'll check the motor and carb and let you know what I find.

 

[mrtoybox]

Re: 20' Almar with Hamilton 773 Jet Drive won't plane with a load

The compression checks out, the carb is clean and so are the plugs. I believe the motor is fine. Thanks for the help guys. I'll keep working on it.

The performance didn't drop when I put the nozzle on. I dug out some of the new foam today to see if it's holding water, and the section I p[ulled out was wet. I called the foam mfg and he says there should be no way with the foam I used it should be holding water. So I'm gonna dig out another chunk tomorrow to see if it is happening in other places. Bummer.... I'll let you know what I find.