1987 Starcraft SS 201

[dozerII]

I have a 1986 StarCraft SS201. I spent the last year rebuilding the entire boat. Here is the specs. 20'8"long 8' beam, weight with fuel and 2 males one fat one skinny 2600#s 1989 4.3 Mercruiser LX 205hp, Current prop Mercruiser # 48-78122-21 I believe it is 14"X 21P, WOT 4200rpm, Gps speed is 38mph. What would the Gurus recommend?

Thanks

 

[steelespike]

Re: 1987 Starcraft SS 201

delete

 

[steelespike]

Re: 1987 Starcraft SS 201

Using a 1.62 gear ratio at 4200 and 38 your slip is 26%,really high. The low rpm could account for some of the slip.
Is the prop worn?Does the boat respond to up trim? I think something isn't right.
It appears you need to drop to a 18" prop to gain about 600 rpm to get you to about 4800 rpm.
While you might need a little less prop I just wonder if the rpm solution is elsewhere.Is the motor healthy?Compression good?Timing
set right and advancing as it should?

 

[dozerII]

Re: 1987 Starcraft SS 201

Using a 1.62 gear ratio at 4200 and 38 your slip is 26%,really high. The low rpm could account for some of the slip.
Is the prop worn?Does the boat respond to up trim? I think something isn't right.
It appears you need to drop to a 18" prop to gain about 600 rpm to get you to about 4800 rpm.
While you might need a little less prop I just wonder if the rpm solution is elsewhere.Is the motor healthy?Compression good?Timing
set right and advancing as it should?

Thanks for the reply SS, the prop is in real good shape, the motor has good compression, and runs well. I have to check the distributer, but the timing is bang on. It responds to up trim but will blow out real easy. When trimmed it almost sounds like the engine is labouring.

 

[bunker108]

Re: 1987 Starcraft SS 201

Hey Dozer...like others have said a drop in pitch is in order. I also run a 4.3 although a slightly lower gear ratio, while I can spin a 21p aluminum to 4600 at wot loaded, but it took forever to plane and blew out quickly with trim. I picked up a 19p 3 blade SS and a 4 blade 19p aluminum and I will water test on Thursday. A 4 blade 18p or 19p SS would probably do well on your big tin boat.

 

[dozerII]

Re: 1987 Starcraft SS 201

Hey Dozer...like others have said a drop in pitch is in order. I also run a 4.3 although a slightly lower gear ratio, while I can spin a 21p aluminum to 4600 at wot loaded, but it took forever to plane and blew out quickly with trim. I picked up a 19p 3 blade SS and a 4 blade 19p aluminum and I will water test on Thursday. A 4 blade 18p or 19p SS would probably do well on your big tin boat.

Thanks 108, I have a few things to try now.

 

[dozerII]

Re: 1987 Starcraft SS 201

Okay I have a little more info. Had the boat out again this time with a 19p, same as the 21p only a mile or two slower, RPM stayed the same. I double checked the timing and it was out so that is now set properly and changed back to the 21p, I picked up 100 rpm and 1mph. I have also found the gear ratio on the drive is 1.84, any suggestions?

 

[steelespike]

Re: 1987 Starcraft SS 201

I think the 21" prop should get you to 4800 which is about 46 mph.
While a little sluggish its possible a 23" prop could get you to about 50.
Assuming it could twist it up to 4800.
Unfortunately it can't get the 21 up to 4800 not to mention a 23.
Did you confirm the timing advances as it should?
Is the outdrive at its original design height?

 

[dozerII]

Re: 1987 Starcraft SS 201

I think the 21" prop should get you to 4800 which is about 46 mph.
While a little sluggish its possible a 23" prop could get you to about 50.
Assuming it could twist it up to 4800.
Unfortunately it can't get the 21 up to 4800 not to mention a 23.
Did you confirm the timing advances as it should?
Is the outdrive at its original design height?

Thanks for the reply Steelespike. as far as the timing advance I don't have a way to check that. There are no advance plates in the distributor as it is a Thnderbolt. I am leaning to a problem with the ignition module.

 

[steelespike]

Re: 1987 Starcraft SS 201

If you have to set the initial timing can't you simply watch the timing as the boat speed advances.
Wouldn't that be one way to indicate a possible module fault?

 

[dozerII]

Re: 1987 Starcraft SS 201

If you have to set the initial timing can't you simply watch the timing as the boat speed advances.
Wouldn't that be one way to indicate a possible module fault?

Kinda a DUH moment for me, Thanks SS that will tell me if I'm getting advance.