I have a mildy built 454 that runs with a mercruiser v6 module. When I tried the v8 module and reset timing etc. I couldn't get te engine to idle or start properly. I was just curious if there is a common reason why it requires the v6 module? Possibly too much cam or carb or not enough?

had same issue with my 454- 420 hp bumped to 485 hp

as soon as I would engage at idle, it would die almost instantly if I was not giving some throttle fast enough, like really quick after engaging. kept it like that 3 years till 2 months before selling. I could not think to sell it like that. was really not a user friendly boat!

So my engine builder came back, switched to V-6 module, retimed the engine and MAGIC !!! I should have done it way before! still have the V-8 module in case some day I need them

he told me , I think, the V-6 module have more advanced timing at idle than the V-8? or opposite? not sure wich but it really solved my problem! I could not believe it!!!

It's been discussed on here a few times. Sometimes running a big cam with a tall prop will cause an engine to want to stumble and die at idle when put into gear. This is especially prevalent when you have it set up to be a little lean at idle to cut down on burning eyes and black transom disease. Running the V6 module allows you to dial in more initial timing because the V6 module introduces a lot less advance, so your total timing will remain about the same. I have been planning to try one in mine because of similar issues. Mine will stay running, but the drop in idle speed is too much, with it idling in neutral at close to 1000 RPM, and dropping to around 650 RPM inn gear. That's hard on the cone clutches.

The v6 -14 module gives a 10* advance curve on a v8 allowing you a lot more initial timing. Very helpful with lower compression, big cam engines. With v6 module your base time can be 24* with a total of 34, even a v8hp module would put you at 44 with that much base timing

been running that for 20years with msd boxes ! merc an riggs been doing that for years! I change plugs just to change plugs

also play with air bleeds and power values