1984 3.7 Mercrusier 470 another hot start issue

[carguy001]

i have read most everything that is out there about this motor and its temperment and have done the following within the last 2 months and still have the hard or now no start after running the boat for 1/2 hour to 1 hr.


new point and condensor
new cap and rotor
new spark plugs
new plug wires
new coil
and rebuilt the carb
adjusted timing runs best at 2 degrees btc

had the boat out on the 5th it ran great for about 2-1/2 hours plenty of power and when we were finished i loaded it on the trailer let it set for about 5 min. after shuting it off and tried to restart it. it was a little hard to start but it did start because it was flooded due to float being a little high. brought the boat home lowered the float 1/16" and took it out an the 6th, boat ran great again as always kids wanted to swim so I shut it down and swam for about 45 min., went to re start and would not start it cranked a little slower than normal so i let it set about 15 mins. cracked the throttle about 1/2 open and it tried to start but backfired, i cranked it 2-3 more times waiting 5 mins between and never did start before the battery seemed to give out. another boater came to help us and he had 2 fully charged batterys so we tried one of his and stilll acted like a dead battery cranked very slow. we got a tow to the ramp and got the boat home the next morning put the muffs on it 1 pump of the throttle with my 1/2 dead battery and she fired right up and ran great.

so now my thoughts are re place the starter but don't think thats my problem or low compression once hot have not check hot yet but cold it is 130-145. also i pulled the #4 plug there was no water in it.

i have done so much and feel i am so close to having this thing trouble free the thought of sinking it or burning keeps crossing my mind


any thoughts i might still have to adjust the float but i am thinking i have block swelling issue?


thanks,

Scott

 

[stonyloam]

Re: 1984 3.7 Mercrusier 470 another hot start issue

As far as the starter goes, 470's have a starter with a rather long armature shaft, that can bend or brake causing the armature to rub against the field coils. Could be your problem.

 

[southwest395]

Re: 1984 3.7 Mercrusier 470 another hot start issue

Sounds like to me you have a bad voltage regulator. Had same issue before. When my voltage regulator was going bad it was over charging the battery. It was charging in between 15 and 16 volts. I would have to let the motor cool down for a hour and half then i could drive again but if shut motor off had same issue again. I didnt have the money to buy a conversion kit to switch to the altenator kit which get rid of the hard start as well. I bought a used voltage regulator and had to replace the impeller. Never had the issue again. The reason why you need to make sure impeller is good. Cause the raw water sucks up from the impeller runs threw a hose to the copper pipe on the voltage regulator to the heat exchanger. The raw water is what cools the voltage regulator.

 

[a1nowell]

Re: 1984 3.7 Mercrusier 470 another hot start issue

carguy,

I have had my 470 since 2008. The 1st year I had it it would do exactly what yours is doing. I cannot explain why but I did the altenator conversion eventhough volt meter read 12-13 volts. After the conversion, I haven't had the hot start problem even once.
www.breezeworks.net

Larry

 

[carguy001]

Re: 1984 3.7 Mercrusier 470 another hot start issue

i forgot to say it already has the alternator conversion done, but i guess it could be over charging as well. i did check the voltage at the alternator at an idle and was get 14.2 volts. so i might need to check it once i am out on the water running at 3000 rpm.

 

[carguy001]

Re: 1984 3.7 Mercrusier 470 another hot start issue

thanks for all quick responses i am going to try to get to the lake one night this week with my brother in-law to run thru some at speed trouble shooting.

 

[southwest395]

Re: 1984 3.7 Mercrusier 470 another hot start issue

Yes cause some alternator system charge different at certain rpms.

i forgot to say it already has the alternator conversion done, but i guess it could be over charging as well. i did check the voltage at the alternator at an idle and was get 14.2 volts. so i might need to check it once i am out on the water running at 3000 rpm.

 

[carguy001]

Re: 1984 3.7 Mercrusier 470 another hot start issue

update on my issue today i ran the boat on the trailer for about 30 mins, before i started it i checked the battery voltage with my dvm and it read 12.53v. i then put the muffs on and started the boat 2 pumps of the throttle she fired up and idled perfect at about 800 rpm i checked the voltage running at the back of the alternator with no electrical items on and the reading was 12.56 volts. i then check the coil volts and it was 8.5v i let run for about 10 mins then ran the rpm up to 1600 rpm and the alternator volts where 13.26v i backed it back down to an idle and turned on the blower and check the voltage at idle and it 14.26v then w the blower on ran it at 1600 rpm and the reading was 14.38 volts returned to idle and volt at alternator was 13.5v and coil volt were 9.2v. i kept the cover closed beteween test to help build heat in the motor and componets. i then shut the boat off waited about a 2 mins she fired right up. so now i am going to let it sit for about 20 mins and try to re-start it and see what happens. my borther in-law and i are heading to the lake tomorrow after work for the lake test to see what happens with a load put on the motor.

 

[Eric 3.7LX Alpha 1]

Re: 1984 3.7 Mercrusier 470 another hot start issue

The coil is suppose to have a lower voltage since you have points. The coil is getting power thru a resistance wire while the key is in the run position, which lowers voltage to extend the life of the points. The coil gets full 12v from the starter solenoid only when cranking the engine thru the purple/yellow wire.

 

[fmalott]

Re: 1984 3.7 Mercrusier 470 another hot start issue

i don't know if this is your problem but you should have 14 volts at idle i would purchase a new alternator first

 

[Eric 3.7LX Alpha 1]

Re: 1984 3.7 Mercrusier 470 another hot start issue

i don't know if this is your problem but you should have 14 volts at idle i would purchase a new alternator first

I think some 1-wire alternators don't charge at idle. The 3-wire alts have the sense wire so they charge at lower RPMS.

 

[carguy001]

Re: 1984 3.7 Mercrusier 470 another hot start issue

after a few more times of letting it run and reving it up to 1500 rpm and letting it sit i got in to act up so that proves it is NOT alergic to the lake water!

it is a 1-wire alternator and found that once i ran the blower and started a few times and let it run it will produce 13.6-13.85v at idle and 1500 rpms

so this last time it cranked normal about 4-5 revs and i stopped cranking checked that i had spark which i do, cranked it again for 3-4 revs and it cranked a little slower i stopped pulled the spark plugs in #1 and #2 cyl. both were a little soot covered and dry, re-installed and pumped the throttle 2 pumps and cranked it about 4-5 revs it was slower cranking but started let it run about a min. shut it off and now it cranks slow like the timing is 30 degrees advanced pulled #1 plug and is dry and has some black soot on it . checked battery volts and they are 12.51v pushed the throttle and have 2 nice streams of fuel.

thanks for all tips and ideas

 

[wrestling coach]

Re: 1984 3.7 Mercrusier 470 another hot start issue

It's my understanding these engines can be hard to crank because of the rather large pistons even though there are only four of them. I am running a group 27 marine cranking battery from NAPA rather than the smaller group 24. You have thrown a lot of parts at this and I am just offering this as a suggestion.

Along similar lines are all points of contact from your battery cables clean and tight? At the battery,starter,ground to block and voltage regulator to starter? Just thinking out loud.

Dennis

 

[carguy001]

Re: 1984 3.7 Mercrusier 470 another hot start issue

you might be onto something Dennis my battery is only 1 year old but is a group 24 with only 675 cca i did look over all the conections at the starter and selonoid the nuts looked a little rusty so i will try disconecting & cleaning those conections and see about borrowing a group 27 battery from a guy i work with he has 3 batterys for his bass boat. i would feel better buying a x-tra battery vs. a starter and alt. and still not fix this issue at 150-250.00 each.

 

[wrestling coach]

Re: 1984 3.7 Mercrusier 470 another hot start issue

Let me also add this. Heat soaking in your starter. This is a common symptom in older engines like C2 Corvette engines of the 60's. Restarting following a run up to temp. Just a thought as well.

Dennis

 

[carguy001]

Re: 1984 3.7 Mercrusier 470 another hot start issue

i was thinking that too and the starter has seen a lot of cranking last year due to the carb flooding issue and this year with chasing the coil issue.

 

[wrestling coach]

Re: 1984 3.7 Mercrusier 470 another hot start issue

Well these things do run in closed spaces. Not a lot of air cooling going on. Heat soaked C2 starters are in similar spaces but can have added exhaust temps from headers and exhaust pipes. Not so much in a boat though.

Try running your blower or open the doghouse for a few minutes as you shut down to swim or have an adult beverage. Pull some of that heat out of that engine area.

In addition. Go inside your distributor and remove the breaker plate that holds your points. Inspect/clean and lightly lube your advance weights and springs. Be sure they work freely. See if you notice any excessive play in the main distributor shaft that might cause your dwell to kind of wander around. Reinstall breaker plate and adjust your dwell carefully. Now put a little more timing in it. Go up to 4*BTDC and see how it behaves.


Dennis

 

[wrestling coach]

Re: 1984 3.7 Mercrusier 470 another hot start issue

you might be onto something Dennis my battery is only 1 year old but is a group 24 with only 675 cca i did look over all the conections at the starter and selonoid the nuts looked a little rusty so i will try disconecting & cleaning those conections and see about borrowing a group 27 battery from a guy i work with he has 3 batterys for his bass boat. i would feel better buying a x-tra battery vs. a starter and alt. and still not fix this issue at 150-250.00 each.

Hit them with some PB Blaster a few minutes before you wrench on them. Put some Dielectric grease on them and retighten. Go easy and take the hot lead off the battery first while you do the rest..

Dennis

 

[carguy001]

Re: 1984 3.7 Mercrusier 470 another hot start issue

well i tried the group 27 battery and cleaned the connections at the starter and selonoid and had the same results once everything got heat soaked it did spin the motor a little fast a little long but after 3 trys of cranking for about 5-6 revs each it was slowed quite a bit and never started. so next place to look at is the distributor check the shaft play and the counter weights. how much side to side play should be acceptable? i have a dial indicator and mag base so i can check the play to with in .001". just by feel in seems to be .010-.015" of play with motor hot.

battery was new 3 months ago and is 715 cca and the guy just used it last sunday

 

[carguy001]

Re: 1984 3.7 Mercrusier 470 another hot start issue

I have now cleaned and lubed the counter weights everything seemed to be in good working order there. i put everything back together set the points gap to .024" and the dwell was @ 31 degrees. 4-5 revs and fired up set the idle to about 750 rpm and set the timing to 5 degrees. boat idled well reved up to 2000 rpm nice let it run about 15 mins shut it off waited about 2 mins fired right up let run for about 5 mins shut it off and let it sit for about 15 mins cranked about 4-5 revs then started cranking slow. waited about 2 mins still cranked slow no start. guess i am going to try a new starter. found a reman for 95.00