20 vs. 25 mid sections

[fantastixvoyage]

My motor has a 25" mid and it appears there is a spacer to make it such. It appears that a 20" would be perfect. How difficult is it to convert with my stock parts or do I have to get all new parts. Also, how do you tell what is the best length for a particular set-up. I have a 20' cat and 25" seemed excessive. Thanks

[Dave S]

What kina cat? Show some Pic't . 25 inch can be made short, just take out the spacer and have the drive shafts cut.You can pull the shift shaft out whithout pulling the power heads, just drive out the rolled pin up top.:)

[fantastixvoyage]

The cat is a 20' Awesome. Check out the "for sale 21 and over". At this point I don't really care if I sell it or not, I just want to enjoy it. Here is my reasoning for thinking the reed is my problem:
It will idle all day long, and I've even used it as a cruiser staying below 3700.
When brought above 3700 it pops out on one cylinder and I'm assuming the bleed system is then carrying the excess, unburned fuel to the other cylinders to cause them to bog as well.

I thought this motor has a high rpm winding for the ignition but I was since told it does not. If you have any other suggestions let me know. The motor seems to have low hours so I'm trying to check all the simple things first.

[Ro Yale]

True you can pull out that 5" extention. Then you will need to shorten the drive shaft, shift shaft and brass water tube. It's not that bad to switch them but it sounds like you have another problem. Don't know what motor you have but it sounds like you could have a bleeder problem or head gasket or scored cylinder. Do a compression check and that will tell you if you have a head gasket or cylinder problem.
Later, Ro:cool:

[fantastixvoyage]

Thanks for the input. I have tried all the basics including compression, fuel pressure, spark, etc. Is there a test for checking high rpm spark? I never got a definite answer if there are high rpm windings for the Merc 3.0L. It bogs at a very specific rpm and it runs better on a trailer than with a load.

[Dave S]

Hi. I did not know you had 3.0s. :o And it has spacers?:confused: Most 3.0s have a 25 inch housing. to have 20 inch is a good start. If the props are too big in pitch, and too low on the boat it can cause bogging problems. Especially with the 1.75 ratios. Did this boat combo ever run fast? 3.0s do not have stator hi speed probs. What year and style motors? I did not find your boat for sale.:confused: Just trying to help.:)

[fantastixvoyage]

Sorry the boat is posted on fastboats.info I was told the majority of the 3.0s come with 25" and so thats what I assumed I had. After measuring it appears its a 20" It would seem that a 15" would be perfect. The prop has been thinned so the pitch numbers are gone so I not sure what pitch it is. It cavitates bad when I try to take off (must feather the gas). The motor is a '95 and I'm not sure of the drive ratio. The boat used to run 80+ easy.