also pre filter 100 microns before the boost pump ----- if you ordered the correct Merc kit then it will come with the boost pump filter ( metal canister filter) . Also cushion clamp that boost pump filter at the installed location.

Thanks BUP, yes the kit appears to come with pump, bracket, filter, filter clamp, electrical connections, plumbing fittings etc.

From what i can tell the bracket for the boost pump itself somehow piggybacks onto the mounting bolts for the fuel/water seperator. I assume the filter can be mounted down low in the bilge on a stringer somewhere.

Here is the data I collected on the fuel pumps. Motors only have 200 hrs

Stbd engine

Just key no motor running. 43 with pump running
After 30 seconds 37psi
After 5 minutes 34psi

With motor running at idle. 37-38
At 3000rpm. 34psi

Port engine

ust key no motor running 44.5
with pump running
After 30 seconds 39
After 5 minutes 34

With motor running at idle. 39
At 3000rpm. 37

Does this look ok?

anyone?

I would replace the fuel pumps and not install the boost pumps. The 500 EFI fuel for system is usually very problem free. I have solved the exact problem you describe by replacing pumps on three different applications over the years. Not really sure why but all were intermittent hot no start and a new pump fixed it. Boost pump makes sense and is probably useful but not sure it's necessary.

I had the same issue with vapor locking after converting from the VST system to the cool fuel system. Ordered the boost pump kit from Merc, installed it and have never had the issue again. That was 9 years ago. Still running on the same cool fuel pump and boost pump with no issues, fwiw..

Thx for the confirmation tgorbett.

Was it a 500EFI that you installed the merc vapor lock kit on? Looking at the instructions they say that the kit is for all Mercruiser V6 and V8 engines. Do you think there will be any issue with installing this on a Mercury Racing 500EFI?

Where are you at anyway ? We are out of vapor lock season here for the most part.
Even the 377 scorpion that is in a sealed box (long story) has been behaving

Meybe you got the early flip to winter blend fuel

Just as a follow up in case anyone else is having a similar issue and does a search:

I installed the merc booster pump kit in my boat over the winter. In the past for the first couple of runs of the season i would see 1-2 vapor lock conditions.

After booster pump installs, I have not seen any vapor lock conditions. Boat has been running great. Booster pumps appear to have solved the problem.

Thanks all