Mercruiser 188 302 (888) 1974 Marlin Libra 21ft

[Marlin74]

I am trying to get just a little more power out of my 188. It is in a 1974 Marlin Libra 21ft with a 19p prop. No i do not want to do an engine swap. I have been trying to find a merc 225 intake manifold so I can go from a 2barrel carb to a 4 barrel carb but i am having no luck. I am looking for some input on cam/intake mainfold and carb set up. I know I need a cam that works well in lower RPM up to about 4200RPM. I am just hesitant to pick one and it not work well with marine application or the set up I am going for. Does any one have any incite or has done any upgrades to a 188? Any recommendation or websites would be a great help!

 

[Bondo]

Ayuh,.... Welcome Aboard,..... When shoppin' for a boat motor cam, look for a grind that builds maximum power from idle, to 5000 rpms,.....

They're usually known in the catalogs as a R/V cam,....

Yer 4200 rpm redline will advance to 4800/ 5000 rpms with a 4 bbl. carb, 'n cam,.....

 

[Marlin74]

Awesome thanks for the reply! It seems like it is slim pickens for cams on some of these sites though.

 

[jones01m]

Marlin,

If I did not toast my 302 I would have put in Comp 31-216-2 cam, dual plane edelbrock 2121 intake, edelbrock 1409 4bbl carb.
This and a set of lifters $700 ish. May also need new rockers, but not sure.
I had this all picked out but found water in cylinders that corroded too deep to machine. I have no experience with this but it was my plan. maybe this helps.

 

[Marlin74]

Jones,

That does help a lot! Thank your for the info!

 

[Marlin74]

Marlin,

If I did not toast my 302 I would have put in Comp 31-216-2 cam, dual plane edelbrock 2121 intake, edelbrock 1409 4bbl carb.
This and a set of lifters $700 ish. May also need new rockers, but not sure.
I had this all picked out but found water in cylinders that corroded too deep to machine. I have no experience with this but it was my plan. maybe this helps.

You don't think that cam would be too big for a 8:1 compression ratio?

 

[jones01m]

I would have thought the 888 to have closer to 8.5:1 or a bit higher. There is a bit of a dish on the pistons, but not sure the volume (10cc?). The previous owner of my 302 had flat top pistons. The head chamber volume should be around 60cc - these are very desirable heads I found out when I posted in the automotive parts portion of CL. Compressed gasket right around .040. Again, I am not an engine expert, but the cam seems pretty close for the flat top pistons, but maybe a bit aggressive on dished pistons. Also, the previous owner of my 888 may have made other mods I was not aware of. I calculated my CR from measurements.

 

[Marlin74]

I would have thought the 888 to have closer to 8.5:1 or a bit higher. There is a bit of a dish on the pistons, but not sure the volume (10cc?). The previous owner of my 302 had flat top pistons. The head chamber volume should be around 60cc - these are very desirable heads I found out when I posted in the automotive parts portion of CL. Compressed gasket right around .040. Again, I am not an engine expert, but the cam seems pretty close for the flat top pistons, but maybe a bit aggressive on dished pistons. Also, the previous owner of my 888 may have made other mods I was not aware of. I calculated my CR from measurements.

Copy that again thank you for the info. It is very helpful!